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Walia A, Shew MA, Varghese J, Lefler SM, Bhat A, Ortmann AJ, Herzog JA, Buchman CA. Electrocochleography-Based Tonotopic Map: II. Frequency-to-Place Mismatch Impacts Speech-Perception Outcomes in Cochlear Implant Recipients. Ear Hear 2024:00003446-990000000-00298. [PMID: 38880958 DOI: 10.1097/aud.0000000000001528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
OBJECTIVES Modern cochlear implants (CIs) use varying-length electrode arrays inserted at varying insertion angles within variably sized cochleae. Thus, there exists an opportunity to enhance CI performance, particularly in postlinguistic adults, by optimizing the frequency-to-place allocation for electrical stimulation, thereby minimizing the need for central adaptation and plasticity. There has been interest in applying Greenwood or Stakhovskaya et al. function (describing the tonotopic map) to postoperative imaging of electrodes to improve frequency allocation and place coding. Acoustically-evoked electrocochleography (ECochG) allows for electrophysiologic best-frequency (BF) determination of CI electrodes and the potential for creating a personalized frequency allocation function. The objective of this study was to investigate the correlation between early speech-perception performance and frequency-to-place mismatch. DESIGN This retrospective study included 50 patients who received a slim perimodiolar electrode array. Following electrode insertion, five acoustic pure-tone stimuli ranging from 0.25 to 2 kHz were presented, and electrophysiological measurements were collected across all 22 electrode contacts. Cochlear microphonic tuning curves were subsequently generated for each stimulus frequency to ascertain the BF electrode or the location corresponding to the maximum response amplitude. Subsequently, we calculated the difference between the stimulus frequency and the patient's CI map's actual frequency allocation at each BF electrode, reflecting the frequency-to-place mismatch. BF electrocochleography-total response (BF-ECochG-TR), a measure of cochlear health, was also evaluated for each subject to control for the known impact of this measure on performance. RESULTS Our findings showed a moderate correlation (r = 0.51; 95% confidence interval: 0.23 to 0.76) between the cumulative frequency-to-place mismatch, as determined using the ECochG-derived BF map (utilizing 500, 1000, and 2000 Hz), and 3-month performance on consonant-nucleus-consonant words (N = 38). Larger positive mismatches, shifted basal from the BF map, led to enhanced speech perception. Incorporating BF-ECochG-TR, total mismatch, and their interaction in a multivariate model explained 62% of the variance in consonant-nucleus-consonant word scores at 3 months. BF-ECochG-TR as a standalone predictor tended to overestimate performance for subjects with larger negative total mismatches and underestimated the performance for those with larger positive total mismatches. Neither cochlear diameter, number of cochlear turns, nor apical insertion angle accounted for the variability in total mismatch. CONCLUSIONS Comparison of ECochG-BF derived tonotopic electrode maps to the frequency allocation tables reveals substantial mismatch, explaining 26.0% of the variability in CI performance in quiet. Closer examination of the mismatch shows that basally shifted maps at high frequencies demonstrate superior performance at 3 months compared with those with apically shifted maps (toward Greenwood and Stakhovskaya et al.). The implications of these results suggest that electrophysiological-based frequency reallocation might lead to enhanced speech-perception performance, especially when compared with conventional manufacturer maps or anatomic-based mapping strategies. Future research, exploring the prospective use of ECochG-based mapping techniques for frequency allocation is underway.
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Affiliation(s)
- Amit Walia
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine in St. Louis, St Louis, Missouri, USA
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Sturm JJ, Ma C, McRackan TR, Schvartz-Leyzac KC. Frequency-to-Place Mismatch Impacts Cochlear Implant Quality of Life, But Not Speech Recognition. Laryngoscope 2024; 134:2898-2905. [PMID: 38214299 PMCID: PMC11078615 DOI: 10.1002/lary.31264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 01/13/2024]
Abstract
OBJECTIVE To retrospectively compare frequency-place mismatch among adult cochlear implant (CI) recipients with lateral wall (LW) and perimodiolar/Mid Scala (PM/MS) arrays, and to quantify the impact of these factors on early post-activation (3 months) speech recognition abilities and CI-specific quality of life. METHODS One hundred and twenty-six adult participants were separated into two groups: (1) 83 participants who underwent CI with a PM/MS array and 43 patients who underwent CI with a LW array. All participants completed the Cochlear Implant Quality of Life Profile (CIQOL-35 Profile) instrument. Angular insertion depth and semitone mismatch, which contribute to frequency-place mismatch, were assessed using post-operative CT scans. Word and speech recognition in quiet were determined using the Consonant-Nucleus-Consonant (CNC) and the AzBio tests, respectively (n = 82 patients). RESULTS LW arrays were more deeply inserted and exhibited less semitone mismatch compared to PM/MS arrays. No significant relationship was found between semitone mismatch and early post-operative speech perception scores for either PM/MS or LW arrays. However, greater degrees of semitone mismatch were associated with lower CIQOL-35 profile scores for PM/MS arrays. CONCLUSIONS AND RELEVANCE The results of this study indicate that both the degree of frequency-place mismatch, and its impact on CI-specific quality of life, vary by CI array design. LEVEL OF EVIDENCE 4 Laryngoscope, 134:2898-2905, 2024.
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Affiliation(s)
- Joshua J Sturm
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, U.S.A
| | - Cheng Ma
- Department of Otolaryngology-Head and Neck Surgery, Penn State College of Medicine, Hershey, Pennsylvania, U.S.A
| | - Theodore R McRackan
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, U.S.A
| | - Kara C Schvartz-Leyzac
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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Fletcher MD, Akis E, Verschuur CA, Perry SW. Improved tactile speech perception using audio-to-tactile sensory substitution with formant frequency focusing. Sci Rep 2024; 14:4889. [PMID: 38418558 PMCID: PMC10901863 DOI: 10.1038/s41598-024-55429-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 02/23/2024] [Indexed: 03/01/2024] Open
Abstract
Haptic hearing aids, which provide speech information through tactile stimulation, could substantially improve outcomes for both cochlear implant users and for those unable to access cochlear implants. Recent advances in wide-band haptic actuator technology have made new audio-to-tactile conversion strategies viable for wearable devices. One such strategy filters the audio into eight frequency bands, which are evenly distributed across the speech frequency range. The amplitude envelopes from the eight bands modulate the amplitudes of eight low-frequency tones, which are delivered through vibration to a single site on the wrist. This tactile vocoder strategy effectively transfers some phonemic information, but vowels and obstruent consonants are poorly portrayed. In 20 participants with normal touch perception, we tested (1) whether focusing the audio filters of the tactile vocoder more densely around the first and second formant frequencies improved tactile vowel discrimination, and (2) whether focusing filters at mid-to-high frequencies improved obstruent consonant discrimination. The obstruent-focused approach was found to be ineffective. However, the formant-focused approach improved vowel discrimination by 8%, without changing overall consonant discrimination. The formant-focused tactile vocoder strategy, which can readily be implemented in real time on a compact device, could substantially improve speech perception for haptic hearing aid users.
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Affiliation(s)
- Mark D Fletcher
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK.
- Institute of Sound and Vibration Research, University of Southampton, University Road, Southampton, SO17 1BJ, UK.
| | - Esma Akis
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK
- Institute of Sound and Vibration Research, University of Southampton, University Road, Southampton, SO17 1BJ, UK
| | - Carl A Verschuur
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK
| | - Samuel W Perry
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK
- Institute of Sound and Vibration Research, University of Southampton, University Road, Southampton, SO17 1BJ, UK
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Creff G, Lambert C, Coudert P, Pean V, Laurent S, Godey B. Comparison of Tonotopic and Default Frequency Fitting for Speech Understanding in Noise in New Cochlear Implantees: A Prospective, Randomized, Double-Blind, Cross-Over Study. Ear Hear 2024; 45:35-52. [PMID: 37823850 DOI: 10.1097/aud.0000000000001423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
OBJECTIVES While cochlear implants (CIs) have provided benefits for speech recognition in quiet for subjects with severe-to-profound hearing loss, speech recognition in noise remains challenging. A body of evidence suggests that reducing frequency-to-place mismatch may positively affect speech perception. Thus, a fitting method based on a tonotopic map may improve speech perception results in quiet and noise. The aim of our study was to assess the impact of a tonotopic map on speech perception in noise and quiet in new CI users. DESIGN A prospective, randomized, double-blind, two-period cross-over study in 26 new CI users was performed over a 6-month period. New CI users older than 18 years with bilateral severe-to-profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on the Greenwood function. Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa. Each setting was maintained for 6 weeks, at the end of which participants performed speech perception tasks. The primary outcome measure was speech recognition in noise. Participants were allocated to sequences by block randomization of size two with a ratio 1:1 (CONSORT Guidelines). Participants and those assessing the outcomes were blinded to the intervention. RESULTS Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (one in each sequence) had to be excluded due to the COVID-19 pandemic. Twenty-four participants were analyzed. Speech recognition in noise was significantly better with the tonotopic fitting at all signal-to-noise ratio (SNR) levels tested [SNR = +9 dB, p = 0.002, mean effect (ME) = 12.1%, 95% confidence interval (95% CI) = 4.9 to 19.2, standardized effect size (SES) = 0.71; SNR = +6 dB, p < 0.001, ME = 16.3%, 95% CI = 9.8 to 22.7, SES = 1.07; SNR = +3 dB, p < 0.001 ME = 13.8%, 95% CI = 6.9 to 20.6, SES = 0.84; SNR = 0 dB, p = 0.003, ME = 10.8%, 95% CI = 4.1 to 17.6, SES = 0.68]. Neither period nor interaction effects were observed for any signal level. Speech recognition in quiet ( p = 0.66) and tonal audiometry ( p = 0.203) did not significantly differ between the two settings. 92% of the participants kept the tonotopy-based map after the study period. No correlation was found between speech-in-noise perception and age, duration of hearing deprivation, angular insertion depth, or position or width of the frequency filters allocated to the electrodes. CONCLUSION For new CI users, tonotopic fitting appears to be more efficient than the default frequency fitting because it allows for better speech recognition in noise without compromising understanding in quiet.
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Affiliation(s)
- Gwenaelle Creff
- Department of Otolaryngology-Head and Neck Surgery (HNS), University Hospital, Rennes, France
- MediCIS, LTSI (Image and Signal Processing Laboratory), INSERM, U1099, Rennes, France
| | - Cassandre Lambert
- Department of Otolaryngology-Head and Neck Surgery (HNS), University Hospital, Rennes, France
| | - Paul Coudert
- Department of Otolaryngology-Head and Neck Surgery (HNS), University Hospital, Rennes, France
| | | | | | - Benoit Godey
- Department of Otolaryngology-Head and Neck Surgery (HNS), University Hospital, Rennes, France
- MediCIS, LTSI (Image and Signal Processing Laboratory), INSERM, U1099, Rennes, France
- Hearing Aid Academy, Javene, France
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Dillon MT, Helpard L, Brown KD, Selleck AM, Richter ME, Rooth MA, Thompson NJ, Dedmon MM, Ladak HM, Agrawal S. Influence of the Frequency-to-Place Function on Recognition with Place-Based Cochlear Implant Maps. Laryngoscope 2023; 133:3540-3547. [PMID: 37078508 DOI: 10.1002/lary.30710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 04/21/2023]
Abstract
OBJECTIVE Comparison of acute speech recognition for cochlear implant (CI) alone and electric-acoustic stimulation (EAS) users listening with default maps or place-based maps using either a spiral ganglion (SG) or a new Synchrotron Radiation-Artificial Intelligence (SR-AI) frequency-to-place function. METHODS Thirteen adult CI-alone or EAS users completed a task of speech recognition at initial device activation with maps that differed in the electric filter frequency assignments. The three map conditions were: (1) maps with the default filter settings (default map), (2) place-based maps with filters aligned to cochlear SG tonotopicity using the SG function (SG place-based map), and (3) place-based maps with filters aligned to cochlear Organ of Corti (OC) tonotopicity using the SR-AI function (SR-AI place-based map). Speech recognition was evaluated using a vowel recognition task. Performance was scored as the percent correct for formant 1 recognition due to the rationale that the maps would deviate the most in the estimated cochlear place frequency for low frequencies. RESULTS On average, participants had better performance with the OC SR-AI place-based map as compared to the SG place-based map and the default map. A larger performance benefit was observed for EAS users than for CI-alone users. CONCLUSION These pilot data suggest that EAS and CI-alone users may experience better performance with a patient-centered mapping approach that accounts for the variability in cochlear morphology (OC SR-AI frequency-to-place function) in the individualization of the electric filter frequencies (place-based mapping procedure). LEVEL OF EVIDENCE 3 Laryngoscope, 133:3540-3547, 2023.
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Affiliation(s)
- Margaret T Dillon
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Luke Helpard
- School of Biomedical Engineering, Western University, London, Ontario, Canada
| | - Kevin D Brown
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - A Morgan Selleck
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Margaret E Richter
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Meredith A Rooth
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Nicholas J Thompson
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Matthew M Dedmon
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Hanif M Ladak
- School of Biomedical Engineering, Western University, London, Ontario, Canada
- Department of Electrical and Computer Engineering, Western University, London, Ontario, Canada
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Department of Otolaryngology - Head & Neck Surgery, Western University, London, Ontario, Canada
| | - Sumit Agrawal
- Department of Otolaryngology - Head & Neck Surgery, Western University, London, Ontario, Canada
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Fletcher MD, Verschuur CA, Perry SW. Improving speech perception for hearing-impaired listeners using audio-to-tactile sensory substitution with multiple frequency channels. Sci Rep 2023; 13:13336. [PMID: 37587166 PMCID: PMC10432540 DOI: 10.1038/s41598-023-40509-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 08/11/2023] [Indexed: 08/18/2023] Open
Abstract
Cochlear implants (CIs) have revolutionised treatment of hearing loss, but large populations globally cannot access them either because of disorders that prevent implantation or because they are expensive and require specialist surgery. Recent technology developments mean that haptic aids, which transmit speech through vibration, could offer a viable low-cost, non-invasive alternative. One important development is that compact haptic actuators can now deliver intense stimulation across multiple frequencies. We explored whether these multiple frequency channels can transfer spectral information to improve tactile phoneme discrimination. To convert audio to vibration, the speech amplitude envelope was extracted from one or more audio frequency bands and used to amplitude modulate one or more vibro-tactile tones delivered to a single-site on the wrist. In 26 participants with normal touch sensitivity, tactile-only phoneme discrimination was assessed with one, four, or eight frequency bands. Compared to one frequency band, performance improved by 5.9% with four frequency bands and by 8.4% with eight frequency bands. The multi-band signal-processing approach can be implemented in real-time on a compact device, and the vibro-tactile tones can be reproduced by the latest compact, low-powered actuators. This approach could therefore readily be implemented in a low-cost haptic hearing aid to deliver real-world benefits.
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Affiliation(s)
- Mark D Fletcher
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK.
- Institute of Sound and Vibration Research, University of Southampton, University Road, Southampton, SO17 1BJ, UK.
| | - Carl A Verschuur
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK
| | - Samuel W Perry
- University of Southampton Auditory Implant Service, University of Southampton, University Road, Southampton, SO17 1BJ, UK
- Institute of Sound and Vibration Research, University of Southampton, University Road, Southampton, SO17 1BJ, UK
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Dillon MT, Buss E, Johnson AD, Canfarotta MW, O’Connell BP. Comparison of Two Place-Based Mapping Procedures on Masked Sentence Recognition as a Function of Electrode Array Angular Insertion Depth and Presence of Acoustic Low-Frequency Information: A Simulation Study. Audiol Neurootol 2023; 28:478-487. [PMID: 37482054 PMCID: PMC10948008 DOI: 10.1159/000531262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 05/23/2023] [Indexed: 07/25/2023] Open
Abstract
INTRODUCTION Cochlear implant (CI) and electric-acoustic stimulation (EAS) users may experience better performance with maps that align the electric filter frequencies to the cochlear place frequencies, known as place-based maps, than with maps that present spectrally shifted information. Individual place-based mapping procedures differ in the frequency content that is aligned to cochlear tonotopicity versus discarded or spectrally shifted. The performance benefit with different place-based maps may vary due to individual differences in angular insertion depth (AID) of the electrode array and whether functional acoustic low-frequency information is available in the implanted ear. The present study compared masked speech recognition with two types of place-based maps as a function of AID and presence of acoustic low-frequency information. METHODS Sixty adults with normal hearing listened acutely to CI or EAS simulations of two types of place-based maps for one of three cases of electrode arrays at shallow AIDs. The strict place-based (Strict-PB) map aligned the low- and mid-frequency information to cochlear tonotopicity and discarded information below the frequency associated with the most apical electrode contact. The alternative place-based map (LFshift-PB) aligned the mid-frequency information to cochlear tonotopicity and provided more of the speech spectrum by compressing low-frequency information on the apical electrode contacts (i.e., <1 kHz). Three actual cases of a 12-channel, 24-mm electrode array were simulated by assigning the carrier frequency for an individual channel as the cochlear place frequency of the associated electrode contact. The AID and cochlear place frequency for the most apical electrode contact were 460° and 498 Hz for case 1, 389° and 728 Hz for case 2, and 335° and 987 Hz for case 3, respectively. RESULTS Generally, better performance was observed with the Strict-PB maps for cases 1 and 2, where mismatches were 2-4 octaves for the most apical channel with the LFshift-PB map. Similar performance was observed between maps for case 3. For the CI simulations, performance with the Strict-PB map declined with decreases in AID, while performance with the LFshift-PB map remained stable across cases. For the EAS simulations, performance with the Strict-PB map remained stable across cases, while performance with the LFshift-PB map improved with decreases in AID. CONCLUSIONS Listeners demonstrated differences with the Strict-PB versus LFshift-PB maps as a function of AID and whether acoustic low-frequency information was available (CI vs. EAS). These data support the use of the Strict-PB mapping procedure for AIDs ≥335°, though further study including time for acclimatization in CI and EAS users is warranted.
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Affiliation(s)
- Margaret T. Dillon
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Emily Buss
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Alec D. Johnson
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Michael W. Canfarotta
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Brendan P. O’Connell
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Charlotte Eye Ear Nose & Throat Associates, P.A., Charlotte, NC, USA
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Dillon MT, Canfarotta MW, Buss E, Rooth MA, Richter ME, Overton AB, Roth NE, Dillon SM, Raymond JH, Young A, Pearson AC, Davis AG, Dedmon MM, Brown KD, O'Connell BP. Influence of Electric Frequency-to-Place Mismatches on the Early Speech Recognition Outcomes for Electric-Acoustic Stimulation Users. Am J Audiol 2023; 32:251-260. [PMID: 36800505 PMCID: PMC10166189 DOI: 10.1044/2022_aja-21-00254] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 05/21/2022] [Accepted: 11/28/2022] [Indexed: 02/19/2023] Open
Abstract
PURPOSE Cochlear implant (CI) recipients with hearing preservation experience significant improvements in speech recognition with electric-acoustic stimulation (EAS) as compared to with a CI alone, although outcomes across EAS users vary. The individual differences in performance may be due in part to default mapping procedures, which result in electric frequency-to-place mismatches for the majority of EAS users. This study assessed the influence of electric mismatches on the early speech recognition for EAS users. METHOD Twenty-one participants were randomized at EAS activation to listen exclusively with a default or place-based map. For both groups, the unaided thresholds determined the acoustic cutoff frequency (i.e., > 65 dB HL). For default maps, the electric filter frequencies were assigned to avoid spectral gaps in frequency information but created varying magnitudes of mismatches. For place-based maps, the electric filter frequencies were assigned to avoid frequency-to-place mismatches. Recognition of consonant-nucleus-consonant words and vowels was assessed at activation and 1, 3, and 6 months postactivation. RESULTS For participants with default maps, electric mismatch at 1500 Hz ranged from 2 to -12.0 semitones (Mdn = -5 semitones). Poorer performance was observed for those with larger magnitudes of electric mismatch. This effect was observed through 6 months of EAS listening experience. CONCLUSIONS The present sample of EAS users experienced better initial performance when electric mismatches were small or eliminated. These data suggest the utility of methods that reduce electric mismatches, such as place-based mapping procedures. Investigation is ongoing to determine whether these differences persist with long-term EAS use. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.22096523.
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Affiliation(s)
- Margaret T. Dillon
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill
| | - Michael W. Canfarotta
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
| | - Emily Buss
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
| | - Meredith A. Rooth
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
| | - Margaret E. Richter
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill
| | | | | | | | | | - Allison Young
- Department of Audiology, UNC Health, Chapel Hill, NC
| | | | - Amanda G. Davis
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, The University of North Carolina at Chapel Hill
| | - Matthew M. Dedmon
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
| | - Kevin D. Brown
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
| | - Brendan P. O'Connell
- Department of Otolaryngology/Head & Neck Surgery, School of Medicine, The University of North Carolina at Chapel Hill
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Dillon MT, O'Connell BP, Canfarotta MW, Buss E, Hopfinger J. Effect of Place-Based Versus Default Mapping Procedures on Masked Speech Recognition: Simulations of Cochlear Implant Alone and Electric-Acoustic Stimulation. Am J Audiol 2022; 31:322-337. [PMID: 35394798 DOI: 10.1044/2022_aja-21-00123] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Cochlear implant (CI) recipients demonstrate variable speech recognition when listening with a CI-alone or electric-acoustic stimulation (EAS) device, which may be due in part to electric frequency-to-place mismatches created by the default mapping procedures. Performance may be improved if the filter frequencies are aligned with the cochlear place frequencies, known as place-based mapping. Performance with default maps versus an experimental place-based map was compared for participants with normal hearing when listening to CI-alone or EAS simulations to observe potential outcomes prior to initiating an investigation with CI recipients. METHOD A noise vocoder simulated CI-alone and EAS devices, mapped with default or place-based procedures. The simulations were based on an actual 24-mm electrode array recipient, whose insertion angles for each electrode contact were used to estimate the respective cochlear place frequency. The default maps used the filter frequencies assigned by the clinical software. The filter frequencies for the place-based maps aligned with the cochlear place frequencies for individual contacts in the low- to mid-frequency cochlear region. For the EAS simulations, low-frequency acoustic information was filtered to simulate aided low-frequency audibility. Performance was evaluated for the AzBio sentences presented in a 10-talker masker at +5 dB signal-to-noise ratio (SNR), +10 dB SNR, and asymptote. RESULTS Performance was better with the place-based maps as compared with the default maps for both CI-alone and EAS simulations. For instance, median performance at +10 dB SNR for the CI-alone simulation was 57% correct for the place-based map and 20% for the default map. For the EAS simulation, those values were 59% and 37% correct. Adding acoustic low-frequency information resulted in a similar benefit for both maps. CONCLUSIONS Reducing frequency-to-place mismatches, such as with the experimental place-based mapping procedure, produces a greater benefit in speech recognition than maximizing bandwidth for CI-alone and EAS simulations. Ongoing work is evaluating the initial and long-term performance benefits in CI-alone and EAS users. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.19529053.
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Affiliation(s)
- Margaret T. Dillon
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
- Division of Speech and Hearing Sciences, Department of Allied Health Sciences, University of North Carolina at Chapel Hill
| | - Brendan P. O'Connell
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Michael W. Canfarotta
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Emily Buss
- Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill
| | - Joseph Hopfinger
- Department of Psychology and Neuroscience, University of North Carolina at Chapel Hill
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Dutrieux N, Quatre R, Péan V, Schmerber S. Correlation Between Cochlear Length, Insertion Angle, and Tonotopic Mismatch for MED-EL FLEX28 Electrode Arrays. Otol Neurotol 2022; 43:48-55. [PMID: 34538852 DOI: 10.1097/mao.0000000000003337] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To investigate the relationship between cochlear length, insertion angle, and tonotopic mismatch and to compare the tonotopic mismatches with respect to the spiral ganglion and the organ of Corti. STUDY DESIGN Retrospective. SETTING Tertiary referral center with cochlear implant program. PATIENTS Analyses of patients' computed tomography images after cochlear implant surgery. INTERVENTION Cochlear implantation with 28-mm-long straight lateral wall electrode arrays. MAIN OUTCOME MEASURE Cochlear length, insertion angle, and insertion depth were assessed using the OTOPLAN software. Tonotopic mismatch for each electrode contact was estimated using the Greenwood (organ of Corti) and the Stakhovskaya (spiral ganglion) maps and compared. RESULTS 106 cochleae were analyzed. 99% of the electrode arrays were located in the tympanic ramp. The insertion was complete in 96% of cases. The mean cochlear length was 34.5 mm and the mean insertion angle of the apical electrode was 545°. Cochlear length was negatively correlated with the insertion angle of the contacts E1 to E9 (all p < 0.004). The tonotopic mismatch was greater at the organ of Corti than at the spiral ganglion. It was also greater at the organ of Corti in larger cochleae (correlation with mismatch for E1 r = 0.421, p < 0.0001) and in the apical than in the middle and basal regions of the cochlea. CONCLUSION Small cochlea size corresponded to higher insertion angle and reduction of tonotopic mismatch on a 28-mm-long straight lateral wall electrode array. Tonotopic mismatch could be minimized preoperatively by choosing electrode arrays according to the individual cochlear morphology and postoperatively by appropriate frequency fitting.
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Affiliation(s)
- Noémie Dutrieux
- Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Grenoble Alpes University Hospital, France
- Medical Faculty, University of Grenoble Alpes, Grenoble, France
| | - Raphaële Quatre
- Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Grenoble Alpes University Hospital, France
- Medical Faculty, University of Grenoble Alpes, Grenoble, France
| | | | - Sébastien Schmerber
- Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Grenoble Alpes University Hospital, France
- Medical Faculty, University of Grenoble Alpes, Grenoble, France
- Brain Tech Inserm Laboratory, UMR 1205, University of Grenoble Alpes, Grenoble, France
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Thomas M, Willis S, Galvin JJ, Fu QJ. Effects of tonotopic matching and spatial cues on segregation of competing speech in simulations of bilateral cochlear implants. PLoS One 2022; 17:e0270759. [PMID: 35788202 PMCID: PMC9255761 DOI: 10.1371/journal.pone.0270759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 06/16/2022] [Indexed: 11/18/2022] Open
Abstract
In the clinical fitting of cochlear implants (CIs), the lowest input acoustic frequency is typically much lower than the characteristic frequency associated with the most apical electrode position, due to the limited electrode insertion depth. For bilateral CI users, electrode positions may differ across ears. However, the same acoustic-to-electrode frequency allocation table (FAT) is typically assigned to both ears. As such, bilateral CI users may experience both intra-aural frequency mismatch within each ear and inter-aural mismatch across ears. This inter-aural mismatch may limit the ability of bilateral CI users to take advantage of spatial cues when attempting to segregate competing speech. Adjusting the FAT to tonotopically match the electrode position in each ear (i.e., increasing the low acoustic input frequency) is theorized to reduce this inter-aural mismatch. Unfortunately, this approach may also introduce the loss of acoustic information below the modified input acoustic frequency. The present study explored the trade-off between reduced inter-aural frequency mismatch and low-frequency information loss for segregation of competing speech. Normal-hearing participants were tested while listening to acoustic simulations of bilateral CIs. Speech reception thresholds (SRTs) were measured for target sentences produced by a male talker in the presence of two different male talkers. Masker speech was either co-located with or spatially separated from the target speech. The bilateral CI simulations were produced by 16-channel sinewave vocoders; the simulated insertion depth was fixed in one ear and varied in the other ear, resulting in an inter-aural mismatch of 0, 2, or 6 mm in terms of cochlear place. Two FAT conditions were compared: 1) clinical (200-8000 Hz in both ears), or 2) matched to the simulated insertion depth in each ear. Results showed that SRTs were significantly lower with the matched than with the clinical FAT, regardless of the insertion depth or spatial configuration of the masker speech. The largest improvement in SRTs with the matched FAT was observed when the inter-aural mismatch was largest (6 mm). These results suggest that minimizing inter-aural mismatch with tonotopically matched FATs may benefit bilateral CI users' ability to segregate competing speech despite substantial low-frequency information loss in ears with shallow insertion depths.
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Affiliation(s)
- Mathew Thomas
- Department of Head and Neck Surgery, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
| | - Shelby Willis
- Department of Head and Neck Surgery, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
| | - John J. Galvin
- House Institute Foundation, Los Angeles, California, United States of America
| | - Qian-Jie Fu
- Department of Head and Neck Surgery, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
- * E-mail:
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Xu K, Willis S, Gopen Q, Fu QJ. Effects of Spectral Resolution and Frequency Mismatch on Speech Understanding and Spatial Release From Masking in Simulated Bilateral Cochlear Implants. Ear Hear 2021; 41:1362-1371. [PMID: 32132377 DOI: 10.1097/aud.0000000000000865] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Due to interaural frequency mismatch, bilateral cochlear-implant (CI) users may be less able to take advantage of binaural cues that normal-hearing (NH) listeners use for spatial hearing, such as interaural time differences and interaural level differences. As such, bilateral CI users have difficulty segregating competing speech even when the target and competing talkers are spatially separated. The goal of this study was to evaluate the effects of spectral resolution, tonotopic mismatch (the frequency mismatch between the acoustic center frequency assigned to CI electrode within an implanted ear relative to the expected spiral ganglion characteristic frequency), and interaural mismatch (differences in the degree of tonotopic mismatch in each ear) on speech understanding and spatial release from masking (SRM) in the presence of competing talkers in NH subjects listening to bilateral vocoder simulations. DESIGN During testing, both target and masker speech were presented in five-word sentences that had the same syntax but were not necessarily meaningful. The sentences were composed of five categories in fixed order (Name, Verb, Number, Color, and Clothes), each of which had 10 items, such that multiple sentences could be generated by randomly selecting a word from each category. Speech reception thresholds (SRTs) for the target sentence presented in competing speech maskers were measured. The target speech was delivered to both ears and the two speech maskers were delivered to (1) both ears (diotic masker), or (2) different ears (dichotic masker: one delivered to the left ear and the other delivered to the right ear). Stimuli included the unprocessed speech and four 16-channel sine-vocoder simulations with different interaural mismatch (0, 1, and 2 mm). SRM was calculated as the difference between the diotic and dichotic listening conditions. RESULTS With unprocessed speech, SRTs were 0.3 and -18.0 dB for the diotic and dichotic maskers, respectively. For the spectrally degraded speech with mild tonotopic mismatch and no interaural mismatch, SRTs were 5.6 and -2.0 dB for the diotic and dichotic maskers, respectively. When the tonotopic mismatch increased in both ears, SRTs worsened to 8.9 and 2.4 dB for the diotic and dichotic maskers, respectively. When the two ears had different tonotopic mismatch (e.g., there was interaural mismatch), the performance drop in SRTs was much larger for the dichotic than for the diotic masker. The largest SRM was observed with unprocessed speech (18.3 dB). With the CI simulations, SRM was significantly reduced to 7.6 dB even with mild tonotopic mismatch but no interaural mismatch; SRM was further reduced with increasing interaural mismatch. CONCLUSIONS The results demonstrate that frequency resolution, tonotopic mismatch, and interaural mismatch have differential effects on speech understanding and SRM in simulation of bilateral CIs. Minimizing interaural mismatch may be critical to optimize binaural benefits and improve CI performance for competing speech, a typical listening environment. SRM (the difference in SRTs between diotic and dichotic maskers) may be a useful clinical tool to assess interaural frequency mismatch in bilateral CI users and to evaluate the benefits of optimization methods that minimize interaural mismatch.
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Affiliation(s)
- Kevin Xu
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, USA
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Frequency-to-Place Mismatch: Characterizing Variability and the Influence on Speech Perception Outcomes in Cochlear Implant Recipients. Ear Hear 2021; 41:1349-1361. [PMID: 32205726 DOI: 10.1097/aud.0000000000000864] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The spatial position of a cochlear implant (CI) electrode array affects the spectral cues provided to the recipient. Differences in cochlear size and array length lead to substantial variability in angular insertion depth (AID) across and within array types. For CI-alone users, the variability in AID results in varying degrees of frequency-to-place mismatch between the default electric frequency filters and cochlear place of stimulation. For electric-acoustic stimulation (EAS) users, default electric frequency filters also vary as a function of residual acoustic hearing in the implanted ear. The present study aimed to (1) investigate variability in AID associated with lateral wall arrays, (2) determine the subsequent frequency-to-place mismatch for CI-alone and EAS users mapped with default frequency filters, and (3) examine the relationship between early speech perception for CI-alone users and two aspects of electrode position: frequency-to-place mismatch and angular separation between neighboring contacts, a metric associated with spectral selectivity at the periphery. DESIGN One hundred one adult CI recipients (111 ears) with MED-EL Flex24 (24 mm), Flex28 (28 mm), and FlexSOFT/Standard (31.5 mm) arrays underwent postoperative computed tomography to determine AID. A subsequent comparison was made between AID, predicted spiral ganglion place frequencies, and the default frequency filters for CI-alone (n = 84) and EAS users (n = 27). For CI-alone users with complete insertions who listened with maps fit with the default frequency filters (n = 48), frequency-to-place mismatch was quantified at 1500 Hz and angular separation between neighboring contacts was determined for electrodes in the 1 to 2 kHz region. Multiple linear regression was used to examine how frequency-to-place mismatch and angular separation of contacts influence consonant-nucleus-consonant (CNC) scores through 6 months postactivation. RESULTS For CI recipients with complete insertions (n = 106, 95.5%), the AID (mean ± standard deviation) of the most apical contact was 428° ± 34.3° for Flex24 (n = 11), 558° ± 65.4° for Flex28 (n = 48), and 636° ± 42.9° for FlexSOFT/Standard (n = 47) arrays. For CI-alone users, default frequency filters aligned closely with the spiral ganglion map for deeply inserted lateral wall arrays. For EAS users, default frequency filters produced a range of mismatches; absolute deviations of ≤ 6 semitones occurred in only 37% of cases. Participants with shallow insertions and minimal or no residual hearing experienced the greatest mismatch. For CI-alone users, both smaller frequency-to-place mismatch and greater angular separation between contacts were associated with better CNC scores during the initial 6 months of device use. CONCLUSIONS There is significant variability in frequency-to-place mismatch among CI-alone and EAS users with default frequency filters, even between individuals implanted with the same array. When using default frequency filters, mismatch can be minimized with longer lateral wall arrays and insertion depths that meet the edge frequency associated with residual hearing for CI-alone and EAS users, respectively. Smaller degrees of frequency-to-place mismatch and decreased peripheral masking due to more widely spaced contacts may independently support better speech perception with longer lateral wall arrays in CI-alone users.
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Assessing the Quality of Low-Frequency Acoustic Hearing: Implications for Combined Electroacoustic Stimulation With Cochlear Implants. Ear Hear 2020; 42:475-486. [PMID: 32976249 DOI: 10.1097/aud.0000000000000949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES There are many potential advantages to combined electric and acoustic stimulation (EAS) with a cochlear implant (CI), including benefits for hearing in noise, localization, frequency selectivity, and music enjoyment. However, performance on these outcome measures is variable, and the residual acoustic hearing may not be beneficial for all patients. As such, we propose a measure of spectral resolution that might be more predictive of the usefulness of the residual hearing than the audiogram alone. In the following experiments, we measured performance on spectral resolution and speech perception tasks in individuals with normal hearing (NH) using low-pass filters to simulate steeply sloping audiograms of typical EAS candidates and compared it with performance on these tasks for individuals with sensorineural hearing loss with similar audiometric configurations. Because listeners with NH had similar levels of audibility and bandwidth to listeners with hearing loss, differences between the groups could be attributed to distortions due to hearing loss. DESIGN Listeners with NH (n = 12) and those with hearing loss (n = 23) with steeply sloping audiograms participated in this study. The group with hearing loss consisted of 7 EAS users, 14 hearing aid users, and 3 who did not use amplification in the test ear. Spectral resolution was measured with the spectral-temporal modulated ripple test (SMRT), and speech perception was measured with AzBio sentences in quiet and noise. Listeners with NH listened to stimuli through low-pass filters and at two levels (40 and 60 dBA) to simulate low and high audibility. Listeners with hearing loss listened to SMRT stimuli unaided at their most comfortable listening level and speech stimuli at 60 dBA. RESULTS Results suggest that performance with SMRT is significantly worse for listeners with hearing loss than for listeners with NH and is not related to audibility. Performance on the speech perception task declined with decreasing frequency information for both listeners with NH and hearing loss. Significant correlations were observed between speech perception, SMRT scores, and mid-frequency audiometric thresholds for listeners with hearing loss. CONCLUSIONS NH simulations describe a "best case scenario" for hearing loss where audibility is the only deficit. For listeners with hearing loss, the likely broadening of auditory filters, loss of cochlear nonlinearities, and possible cochlear dead regions may have contributed to distorted spectral resolution and thus deviations from the NH simulations. Measures of spectral resolution may capture an aspect of hearing loss not evident from the audiogram and be a useful tool for assessing the contributions of residual hearing post-cochlear implantation.
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Newman RS, Morini G, Shroads E, Chatterjee M. Toddlers' fast-mapping from noise-vocoded speech. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 147:2432. [PMID: 32359241 PMCID: PMC7176458 DOI: 10.1121/10.0001129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/02/2020] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
The ability to recognize speech that is degraded spectrally is a critical skill for successfully using a cochlear implant (CI). Previous research has shown that toddlers with normal hearing can successfully recognize noise-vocoded words as long as the signal contains at least eight spectral channels [Newman and Chatterjee. (2013). J. Acoust. Soc. Am. 133(1), 483-494; Newman, Chatterjee, Morini, and Remez. (2015). J. Acoust. Soc. Am. 138(3), EL311-EL317], although they have difficulty with signals that only contain four channels of information. Young children with CIs not only need to match a degraded speech signal to a stored representation (word recognition), but they also need to create new representations (word learning), a task that is likely to be more cognitively demanding. Normal-hearing toddlers aged 34 months were tested on their ability to initially learn (fast-map) new words in noise-vocoded stimuli. While children were successful at fast-mapping new words from 16-channel noise-vocoded stimuli, they failed to do so from 8-channel noise-vocoded speech. The level of degradation imposed by 8-channel vocoding appears sufficient to disrupt fast-mapping in young children. Recent results indicate that only CI patients with high spectral resolution can benefit from more than eight active electrodes. This suggests that for many children with CIs, reduced spectral resolution may limit their acquisition of novel words.
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Affiliation(s)
- Rochelle S Newman
- Department of Hearing and Speech Sciences, University of Maryland, 0100 Lefrak Hall, College Park, Maryland 20742, USA
| | - Giovanna Morini
- Department of Communication Sciences and Disorders, University of Delaware, 100 Discovery Boulevard, Newark, Delaware 19713, USA
| | - Emily Shroads
- Department of Hearing and Speech Sciences, University of Maryland, 0100 Lefrak Hall, College Park, Maryland 20742, USA
| | - Monita Chatterjee
- Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA
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The Effect of Simulated Interaural Frequency Mismatch on Speech Understanding and Spatial Release From Masking. Ear Hear 2019; 39:895-905. [PMID: 29337763 DOI: 10.1097/aud.0000000000000541] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The binaural-hearing system interaurally compares inputs, which underlies the ability to localize sound sources and to better understand speech in complex acoustic environments. Cochlear implants (CIs) are provided in both ears to increase binaural-hearing benefits; however, bilateral CI users continue to struggle with understanding speech in the presence of interfering sounds and do not achieve the same level of spatial release from masking (SRM) as normal-hearing listeners. One reason for diminished SRM in CI users could be that the electrode arrays are inserted at different depths in each ear, which would cause an interaural frequency mismatch. Because interaural frequency mismatch diminishes the salience of interaural differences for relatively simple stimuli, it may also diminish binaural benefits for spectral-temporally complex stimuli like speech. This study evaluated the effect of simulated frequency-to-place mismatch on speech understanding and SRM. DESIGN Eleven normal-hearing listeners were tested on a speech understanding task. There was a female target talker who spoke five-word sentences from a closed set of words. There were two interfering male talkers who spoke unrelated sentences. Nonindividualized head-related transfer functions were used to simulate a virtual auditory space. The target was presented from the front (0°), and the interfering speech was either presented from the front (colocated) or from 90° to the right (spatially separated). Stimuli were then processed by an eight-channel vocoder with tonal carriers to simulate aspects of listening through a CI. Frequency-to-place mismatch ("shift") was introduced by increasing the center frequency of the synthesis filters compared with the corresponding analysis filters. Speech understanding was measured for different shifts (0, 3, 4.5, and 6 mm) and target-to-masker ratios (TMRs: +10 to -10 dB). SRM was calculated as the difference in the percentage of correct words for the colocated and separated conditions. Two types of shifts were tested: (1) bilateral shifts that had the same frequency-to-place mismatch in both ears, but no interaural frequency mismatch, and (2) unilateral shifts that produced an interaural frequency mismatch. RESULTS For the bilateral shift conditions, speech understanding decreased with increasing shift and with decreasing TMR, for both colocated and separate conditions. There was, however, no interaction between shift and spatial configuration; in other words, SRM was not affected by shift. For the unilateral shift conditions, speech understanding decreased with increasing interaural mismatch and with decreasing TMR for both the colocated and spatially separated conditions. Critically, there was a significant interaction between the amount of shift and spatial configuration; in other words, SRM decreased for increasing interaural mismatch. CONCLUSIONS A frequency-to-place mismatch in one or both ears resulted in decreased speech understanding. SRM, however, was only affected in conditions with unilateral shifts and interaural frequency mismatch. Therefore, matching frequency information between the ears provides listeners with larger binaural-hearing benefits, for example, improved speech understanding in the presence of interfering talkers. A clinical procedure to reduce interaural frequency mismatch when programming bilateral CIs may improve benefits in speech segregation that are due to binaural-hearing abilities.
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Patro C, Mendel LL. Gated Word Recognition by Postlingually Deafened Adults With Cochlear Implants: Influence of Semantic Context. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2018; 61:145-158. [PMID: 29242894 DOI: 10.1044/2017_jslhr-h-17-0141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 08/28/2017] [Indexed: 06/07/2023]
Abstract
PURPOSE The main goal of this study was to investigate the minimum amount of sensory information required to recognize spoken words (isolation points [IPs]) in listeners with cochlear implants (CIs) and investigate facilitative effects of semantic contexts on the IPs. METHOD Listeners with CIs as well as those with normal hearing (NH) participated in the study. In Experiment 1, the CI users listened to unprocessed (full-spectrum) stimuli and individuals with NH listened to full-spectrum or vocoder processed speech. IPs were determined for both groups who listened to gated consonant-nucleus-consonant words that were selected based on lexical properties. In Experiment 2, the role of semantic context on IPs was evaluated. Target stimuli were chosen from the Revised Speech Perception in Noise corpus based on the lexical properties of the final words. RESULTS The results indicated that spectrotemporal degradations impacted IPs for gated words adversely, and CI users as well as participants with NH listening to vocoded speech had longer IPs than participants with NH who listened to full-spectrum speech. In addition, there was a clear disadvantage due to lack of semantic context in all groups regardless of the spectral composition of the target speech (full spectrum or vocoded). Finally, we showed that CI users (and users with NH with vocoded speech) can overcome such word processing difficulties with the help of semantic context and perform as well as listeners with NH. CONCLUSION Word recognition occurs even before the entire word is heard because listeners with NH associate an acoustic input with its mental representation to understand speech. The results of this study provide insight into the role of spectral degradation on the processing of spoken words in isolation and the potential benefits of semantic context. These results may also explain why CI users rely substantially on semantic context.
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Affiliation(s)
| | - Lisa Lucks Mendel
- School of Communication Sciences & Disorders, University of Memphis, TN
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Integration of acoustic and electric hearing is better in the same ear than across ears. Sci Rep 2017; 7:12500. [PMID: 28970567 PMCID: PMC5624923 DOI: 10.1038/s41598-017-12298-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 09/06/2017] [Indexed: 11/26/2022] Open
Abstract
Advances in cochlear implant (CI) technology allow for acoustic and electric hearing to be combined within the same ear (electric-acoustic stimulation, or EAS) and/or across ears (bimodal listening). Integration efficiency (IE; the ratio between observed and predicted performance for acoustic-electric hearing) can be used to estimate how well acoustic and electric hearing are combined. The goal of this study was to evaluate factors that affect IE in EAS and bimodal listening. Vowel recognition was measured in normal-hearing subjects listening to simulations of unimodal, EAS, and bimodal listening. The input/output frequency range for acoustic hearing was 0.1–0.6 kHz. For CI simulations, the output frequency range was 1.2–8.0 kHz to simulate a shallow insertion depth and the input frequency range was varied to provide increasing amounts of speech information and tonotopic mismatch. Performance was best when acoustic and electric hearing was combined in the same ear. IE was significantly better for EAS than for bimodal listening; IE was sensitive to tonotopic mismatch for EAS, but not for bimodal listening. These simulation results suggest acoustic and electric hearing may be more effectively and efficiently combined within rather than across ears, and that tonotopic mismatch should be minimized to maximize the benefit of acoustic-electric hearing, especially for EAS.
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20
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Shannon RV. Auditory implant research at the House Ear Institute 1989-2013. Hear Res 2015; 322:57-66. [PMID: 25449009 PMCID: PMC4380593 DOI: 10.1016/j.heares.2014.11.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 11/04/2014] [Accepted: 11/07/2014] [Indexed: 11/29/2022]
Abstract
The House Ear Institute (HEI) had a long and distinguished history of auditory implant innovation and development. Early clinical innovations include being one of the first cochlear implant (CI) centers, being the first center to implant a child with a cochlear implant in the US, developing the auditory brainstem implant, and developing multiple surgical approaches and tools for Otology. This paper reviews the second stage of auditory implant research at House - in-depth basic research on perceptual capabilities and signal processing for both cochlear implants and auditory brainstem implants. Psychophysical studies characterized the loudness and temporal perceptual properties of electrical stimulation as a function of electrical parameters. Speech studies with the noise-band vocoder showed that only four bands of tonotopically arrayed information were sufficient for speech recognition, and that most implant users were receiving the equivalent of 8-10 bands of information. The noise-band vocoder allowed us to evaluate the effects of the manipulation of the number of bands, the alignment of the bands with the original tonotopic map, and distortions in the tonotopic mapping, including holes in the neural representation. Stimulation pulse rate was shown to have only a small effect on speech recognition. Electric fields were manipulated in position and sharpness, showing the potential benefit of improved tonotopic selectivity. Auditory training shows great promise for improving speech recognition for all patients. And the Auditory Brainstem Implant was developed and improved and its application expanded to new populations. Overall, the last 25 years of research at HEI helped increase the basic scientific understanding of electrical stimulation of hearing and contributed to the improved outcomes for patients with the CI and ABI devices. This article is part of a Special Issue entitled .
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Affiliation(s)
- Robert V Shannon
- Department of Otolaryngology, University of Southern California, Keck School of Medicine of USC, 806 W. Adams Blvd, Los Angeles, CA 90007-2505, USA.
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Whitmal NA, DeMaio D, Lin R. Effects of envelope bandwidth on importance functions for cochlear implant simulations. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 137:733-744. [PMID: 25698008 DOI: 10.1121/1.4906260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Frequency-importance functions (FIFs) quantify intelligibility contributions of spectral regions of speech. In previous work, FIFs were considered as instruments for characterizing intelligibility contributions of individual cochlear implant electrode channels. Comparisons of FIFs for natural speech and vocoder-simulated implant processed speech showed that vocoding shifted peak importance regions downward in frequency by 0.5 octaves. These shifts were attributed to voicing cue changes, and may reflect increased reliance on low-frequency information (apart from periodicity cues) for correct voicing perception. The purpose of this study was to determine whether increasing channel envelope bandwidth would reverse these shifts by improving access to voicing and pitch cues. Importance functions were measured for 48 subjects with normal hearing, who listened to vowel-consonant-vowel tokens either as recorded or as output from five different vocoders that simulated implant processing. Envelopes were constructed using filters that either included or excluded pitch information. Results indicate that vocoding-based shifts are only partially counteracted by including pitch information; moreover, a substantial baseline shift is present even for vocoders with high spectral resolution. The results also suggest that vocoded speech intelligibility is most sensitive to a loss of spectral resolution in high-importance regions, a finding with possible implications for cochlear implant electrode mapping.
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Affiliation(s)
- Nathaniel A Whitmal
- Department of Communication Disorders, University of Massachusetts, Amherst, Massachusetts 01003
| | - Decia DeMaio
- Department of Communication Disorders, University of Massachusetts, Amherst, Massachusetts 01003
| | - Rongheng Lin
- Division of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts 01003
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Fuller CD, Galvin JJ, Maat B, Free RH, Başkent D. The musician effect: does it persist under degraded pitch conditions of cochlear implant simulations? Front Neurosci 2014; 8:179. [PMID: 25071428 PMCID: PMC4075350 DOI: 10.3389/fnins.2014.00179] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 06/08/2014] [Indexed: 12/05/2022] Open
Abstract
Cochlear implants (CIs) are auditory prostheses that restore hearing via electrical stimulation of the auditory nerve. Compared to normal acoustic hearing, sounds transmitted through the CI are spectro-temporally degraded, causing difficulties in challenging listening tasks such as speech intelligibility in noise and perception of music. In normal hearing (NH), musicians have been shown to better perform than non-musicians in auditory processing and perception, especially for challenging listening tasks. This “musician effect” was attributed to better processing of pitch cues, as well as better overall auditory cognitive functioning in musicians. Does the musician effect persist when pitch cues are degraded, as it would be in signals transmitted through a CI? To answer this question, NH musicians and non-musicians were tested while listening to unprocessed signals or to signals processed by an acoustic CI simulation. The task increasingly depended on pitch perception: (1) speech intelligibility (words and sentences) in quiet or in noise, (2) vocal emotion identification, and (3) melodic contour identification (MCI). For speech perception, there was no musician effect with the unprocessed stimuli, and a small musician effect only for word identification in one noise condition, in the CI simulation. For emotion identification, there was a small musician effect for both. For MCI, there was a large musician effect for both. Overall, the effect was stronger as the importance of pitch in the listening task increased. This suggests that the musician effect may be more rooted in pitch perception, rather than in a global advantage in cognitive processing (in which musicians would have performed better in all tasks). The results further suggest that musical training before (and possibly after) implantation might offer some advantage in pitch processing that could partially benefit speech perception, and more strongly emotion and music perception.
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Affiliation(s)
- Christina D Fuller
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen Groningen, Netherlands ; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen Groningen, Netherlands
| | - John J Galvin
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen Groningen, Netherlands ; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen Groningen, Netherlands ; Division of Communication and Auditory Neuroscience, House Research Institute Los Angeles, CA, USA ; Department of Head and Neck Surgery, David Geffen School of Medicine, UCLA Los Angeles, CA, USA
| | - Bert Maat
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen Groningen, Netherlands ; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen Groningen, Netherlands
| | - Rolien H Free
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen Groningen, Netherlands ; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen Groningen, Netherlands
| | - Deniz Başkent
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen Groningen, Netherlands ; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen Groningen, Netherlands
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Place pitch versus electrode location in a realistic computational model of the implanted human cochlea. Hear Res 2014; 315:10-24. [PMID: 24975087 DOI: 10.1016/j.heares.2014.06.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 06/06/2014] [Accepted: 06/15/2014] [Indexed: 11/23/2022]
Abstract
Place pitch was investigated in a computational model of the implanted human cochlea containing nerve fibres with realistic trajectories that take the variable distance between the organ of Corti and spiral ganglion into account. The model was further updated from previous studies by including fluid compartments in the modiolus and updating the electrical conductivity values of (temporal) bone and the modiolus, based on clinical data. Four different cochlear geometries are used, modelled with both lateral and perimodiolar implants, and their neural excitation patterns were examined for nerve fibres modelled with and without peripheral processes. Additionally, equations were derived from the model geometries that describe Greenwood's frequency map as a function of cochlear angle at the basilar membrane as well as at the spiral ganglion. The main findings are: (I) in the first (basal) turn of the cochlea, cochlear implant induced pitch can be predicted fairly well using the Greenwood function. (II) Beyond the first turn this pitch becomes increasingly unpredictable, greatly dependent on stimulus level, state of the cochlear neurons and the electrode's distance from the modiolus. (III) After the first turn cochlear implant induced pitch decreases as stimulus level increases, but the pitch does not reach values expected from direct spiral ganglion stimulation unless the peripheral processes are missing. (IV) Electrode contacts near the end of the spiral ganglion or deeper elicit very unpredictable pitch, with broad frequency ranges that strongly overlap with those of neighbouring contacts. (V) The characteristic place pitch for stimulation at either the organ of Corti or the spiral ganglion can be described as a function of cochlear angle by the equations presented in this paper.
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Pals C, Sarampalis A, Baskent D. Listening effort with cochlear implant simulations. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2013; 56:1075-1084. [PMID: 23275424 DOI: 10.1044/1092-4388(2012/12-0074)] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
PURPOSE Fitting a cochlear implant (CI) for optimal speech perception does not necessarily optimize listening effort. This study aimed to show that listening effort may change between CI processing conditions for which speech intelligibility remains constant. METHOD Nineteen normal-hearing participants listened to CI simulations with varying numbers of spectral channels. A dual-task paradigm combining an intelligibility task with either a linguistic or nonlinguistic visual response-time (RT) task measured intelligibility and listening effort. The simultaneously performed tasks compete for limited cognitive resources; changes in effort associated with the intelligibility task are reflected in changes in RT on the visual task. A separate self-report scale provided a subjective measure of listening effort. RESULTS All measures showed significant improvements with increasing spectral resolution up to 6 channels. However, only the RT measure of listening effort continued improving up to 8 channels. The effects were stronger for RTs recorded during listening than for RTs recorded between listening. CONCLUSION The results suggest that listening effort decreases with increased spectral resolution. Moreover, these improvements are best reflected in objective measures of listening effort, such as RTs on a secondary task, rather than intelligibility scores or subjective effort measures.
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Affiliation(s)
- Carina Pals
- University Medical Center Groningen, the Netherlands.
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25
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Newman R, Chatterjee M. Toddlers' recognition of noise-vocoded speech. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 133:483-94. [PMID: 23297920 PMCID: PMC3548833 DOI: 10.1121/1.4770241] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2011] [Revised: 11/10/2012] [Accepted: 11/14/2012] [Indexed: 05/15/2023]
Abstract
Despite their remarkable clinical success, cochlear-implant listeners today still receive spectrally degraded information. Much research has examined normally hearing adult listeners' ability to interpret spectrally degraded signals, primarily using noise-vocoded speech to simulate cochlear implant processing. Far less research has explored infants' and toddlers' ability to interpret spectrally degraded signals, despite the fact that children in this age range are frequently implanted. This study examines 27-month-old typically developing toddlers' recognition of noise-vocoded speech in a language-guided looking study. Children saw two images on each trial and heard a voice instructing them to look at one item ("Find the cat!"). Full-spectrum sentences or their noise-vocoded versions were presented with varying numbers of spectral channels. Toddlers showed equivalent proportions of looking to the target object with full-speech and 24- or 8-channel noise-vocoded speech; they failed to look appropriately with 2-channel noise-vocoded speech and showed variable performance with 4-channel noise-vocoded speech. Despite accurate looking performance for speech with at least eight channels, children were slower to respond appropriately as the number of channels decreased. These results indicate that 2-yr-olds have developed the ability to interpret vocoded speech, even without practice, but that doing so requires additional processing. These findings have important implications for pediatric cochlear implantation.
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Affiliation(s)
- Rochelle Newman
- Department of Hearing and Speech Sciences, 0100 Lefrak Hall, University of Maryland, College Park, Maryland 20742, USA.
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Strydom T, Hanekom JJ. An analysis of the effects of electrical field interaction with an acoustic model of cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 129:2213-2226. [PMID: 21476676 DOI: 10.1121/1.3518761] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Electrical field interaction caused by current spread in a cochlear implant was modeled in an explicit way in an acoustic model (the SPREAD model) presented to six listeners with normal hearing. The typical processing of cochlear implants was modeled more closely than in traditional acoustic models by careful selection of parameters related to current spread or parameters that could amplify the electrical field interactions caused by current spread. These parameters were the insertion depth, electrode spacing, electrical dynamic range, and dynamic range compression function. The hypothesis was that current spread could account for the asymptote in performance in speech intelligibility experiments observed at around seven stimulation channels in a number of cochlear implant studies. Speech intelligibility for sentences, vowels, and consonants at three noise levels (SNR of +15 dB, +10 dB, and +5 dB) was measured as a function of the number of spectral channels (4, 7, and 16). The SPREAD model appears to explain the asymptote in speech intelligibility at seven channels for all noise levels for all speech material used in this study. It is shown that the compressive amplitude mapping used in cochlear implants can have a detrimental effect on the number of effective channels.
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Affiliation(s)
- Trudie Strydom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, Gauteng 0002, South Africa
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Strydom T, Hanekom JJ. The performance of different synthesis signals in acoustic models of cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 129:920-933. [PMID: 21361449 DOI: 10.1121/1.3518760] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Synthesis (carrier) signals in acoustic models embody assumptions about perception of auditory electric stimulation. This study compared speech intelligibility of consonants and vowels processed through a set of nine acoustic models that used Spectral Peak (SPEAK) and Advanced Combination Encoder (ACE)-like speech processing, using synthesis signals which were representative of signals used previously in acoustic models as well as two new ones. Performance of the synthesis signals was determined in terms of correspondence with cochlear implant (CI) listener results for 12 attributes of phoneme perception (consonant and vowel recognition; F1, F2, and duration information transmission for vowels; voicing, manner, place of articulation, affrication, burst, nasality, and amplitude envelope information transmission for consonants) using four measures of performance. Modulated synthesis signals produced the best correspondence with CI consonant intelligibility, while sinusoids, narrow noise bands, and varying noise bands produced the best correspondence with CI vowel intelligibility. The signals that performed best overall (in terms of correspondence with both vowel and consonant attributes) were modulated and unmodulated noise bands of varying bandwidth that corresponded to a linearly varying excitation width of 0.4 mm at the apical to 8 mm at the basal channels.
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Affiliation(s)
- Trudie Strydom
- Department of Electrical, Electronic, and Computer Engineering, University of Pretoria, Pretoria 0002, South Africa
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Välimaa TT, Sorri MJ, Laitakari J, Sivonen V, Muhli A. Vowel confusion patterns in adults during initial 4 years of implant use. CLINICAL LINGUISTICS & PHONETICS 2011; 25:121-144. [PMID: 21070135 DOI: 10.3109/02699206.2010.514692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This study investigated adult cochlear implant users' (n = 39) vowel recognition and confusions by an open-set syllable test during 4 years of implant use, in a prospective repeated-measures design. Subjects' responses were coded for phoneme errors and estimated by the generalized mixed model. Improvement in overall vowel recognition was highest during the first 6 months, showing statistically significant change until 4 years, especially for the mediocre performers. The best performers improved statistically significantly until 18 months. The poorest performers improved until 12 months and exhibited more vowel confusions. No differences were found in overall vowel recognition between Nucleus24M/24R and Med-ElC40+ device users (matched comparison), but certain vowels showed statistically significant differences. Vowel confusions between adjacent vowels were evident, probably due to the implant users' inability to discriminate formant frequencies. Vowel confusions were also dominated by vowels whose average F1 and/or F2 frequencies were higher than the target vowel, indicating a basalward shift in the confusions.
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Affiliation(s)
- Taina T Välimaa
- Faculty of Humanities, Logopedics, and Department of Otorhinolaryngology. Oulu University Hospital, University of Oulu, Finland.
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Interactions between unsupervised learning and the degree of spectral mismatch on short-term perceptual adaptation to spectrally shifted speech. Ear Hear 2010; 30:238-49. [PMID: 19194293 DOI: 10.1097/aud.0b013e31819769ac] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Cochlear implant listeners are able to at least partially adapt to the spectral mismatch associated with the implant device and speech processor via daily exposure and/or explicit training. The overall goal of this study was to investigate interactions between short-term unsupervised learning (i.e., passive adaptation) and the degree of spectral mismatch in normal-hearing listeners' adaptation to spectrally shifted vowels. DESIGN Normal-hearing subjects were tested while listening to acoustic cochlear implant simulations. Unsupervised learning was measured by testing vowel recognition repeatedly over a 5 day period; no feedback or explicit training was provided. In experiment 1, subjects listened to 8-channel, sine-wave vocoded speech. The spectral envelope was compressed to simulate a 16 mm cochlear implant electrode array. The analysis bands were fixed and the compressed spectral envelope was linearly shifted toward the base by 3.6, 6, or 8.3 mm to simulate different insertion depths of the electrode array, resulting in a slight, moderate, or severe spectral shift. In experiment 2, half the subjects were exclusively exposed to a severe shift with 8 or 16 channels (exclusive groups), and half the subjects were exposed to 8-channel severely shifted speech, 16-channel severely shifted speech, and 8-channel moderately shifted speech, alternately presented within each test session (mixed group). The region of stimulation in the cochlea was fixed (16 mm in extent and 15 mm from the apex) and the analysis bands were manipulated to create the spectral shift conditions. To determine whether increased spectral resolution would improve adaptation, subjects were exposed to 8- or 16-channel severely shifted speech. RESULTS In experiment 1, at the end of the adaptation period, there was no significant difference between 8-channel speech that was spectrally matched and that shifted by 3.6 mm. There was a significant, but less-complete, adaptation to the 6 mm shift and no adaptation to the 8.3 mm shift. In experiment 2, for the mixed exposure group, there was significant adaptation to severely shifted speech with 8 channels and even greater adaptation with 16 channels. For the exclusive exposure group, there was no significant adaptation to severely shifted speech with either 8 or 16 channels. CONCLUSIONS These findings suggest that listeners are able to passively adapt to spectral shifts up to 6 mm. For spectral shifts beyond 6 mm, some passive adaptation was observed with mixed exposure to a smaller spectral shift, even at the expense of some low frequency information. Mixed exposure to the smaller shift may have enhanced listeners' access to spectral envelope details that were not accessible when listening exclusively to severely shifted speech. The results suggest that the range of spectral mismatch that can support passive adaptation may be larger than previously reported. Some amount of passive adaptation may be possible with severely shifted speech by exposing listeners to a relatively small mismatch in conjunction with the severe mismatch.
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Li T, Fu QJ. Effects of spectral shifting on speech perception in noise. Hear Res 2010; 270:81-8. [PMID: 20868733 DOI: 10.1016/j.heares.2010.09.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 09/08/2010] [Accepted: 09/14/2010] [Indexed: 11/16/2022]
Abstract
The present study used eight normal-hearing (NH) subjects, listening to acoustic cochlear implant (CI) simulations, to examine the effects of spectral shifting on speech recognition in noise. Speech recognition was measured using spectrally matched and shifted speech (vowels, consonants, and IEEE sentences), generated by 8-channel, sine-wave vocoder. Measurements were made in quiet and in noise (speech-shaped static noise and speech-babble at 5 dB signal-to-noise ratio). One spectral match condition and four spectral shift conditions were investigated: 2 mm, 3 mm, and 4 mm linear shift, and 3 mm shift with compression, in terms of cochlear distance. Results showed that speech recognition scores dropped because of noise and spectral shifting, and that the interactive effects of spectral shifting and background conditions depended on the degree/type of spectral shift, background conditions, and the speech test materials. There was no significant interaction between spectral shifting and two noise conditions for all speech test materials. However, significant interactions between linear spectral shifts and all background conditions were found in sentence recognition; significant interactions between spectral shift types and all background conditions were found in vowel recognition. Overall, the results suggest that tonotopic mismatch may affect performance of CI users in complex listening environments.
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Affiliation(s)
- Tianhao Li
- Division of Communication and Auditory Neuroscience, House Ear Institute, Los Angeles, CA 90057, USA.
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31
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Improving melody recognition in cochlear implant recipients through individualized frequency map fitting. Eur Arch Otorhinolaryngol 2010; 268:27-39. [DOI: 10.1007/s00405-010-1335-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 07/02/2010] [Indexed: 10/19/2022]
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Garadat SN, Litovsky RY, Yu G, Zeng FG. Role of binaural hearing in speech intelligibility and spatial release from masking using vocoded speech. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2009; 126:2522-35. [PMID: 19894832 PMCID: PMC2787072 DOI: 10.1121/1.3238242] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A cochlear implant vocoder was used to evaluate relative contributions of spectral and binaural temporal fine-structure cues to speech intelligibility. In Study I, stimuli were vocoded, and then convolved through head related transfer functions (HRTFs) to remove speech temporal fine structure but preserve the binaural temporal fine-structure cues. In Study II, the order of processing was reversed to remove both speech and binaural temporal fine-structure cues. Speech reception thresholds (SRTs) were measured adaptively in quiet, and with interfering speech, for unprocessed and vocoded speech (16, 8, and 4 frequency bands), under binaural or monaural (right-ear) conditions. Under binaural conditions, as the number of bands decreased, SRTs increased. With decreasing number of frequency bands, greater benefit from spatial separation of target and interferer was observed, especially in the 8-band condition. The present results demonstrate a strong role of the binaural cues in spectrally degraded speech, when the target and interfering speech are more likely to be confused. The nearly normal binaural benefits under present simulation conditions and the lack of order of processing effect further suggest that preservation of binaural cues is likely to improve performance in bilaterally implanted recipients.
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Affiliation(s)
- Soha N Garadat
- Waisman Center, University of Wisconsin, Madison, WI 53705, USA
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Goupell MJ, Laback B, Majdak P, Baumgartner WD. Effects of upper-frequency boundary and spectral warping on speech intelligibility in electrical stimulation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 123:2295-309. [PMID: 18397034 PMCID: PMC3061454 DOI: 10.1121/1.2831738] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Speech understanding was tested for seven listeners using 12-electrode Med-El cochlear implants (CIs) and six normal-hearing listeners using a CI simulation. Eighteen different types of processing were evaluated, which varied the frequency-to-tonotopic place mapping and the upper boundary of the frequency and stimulation range. Spectrally unwarped and warped conditions were included. Unlike previous studies on this topic, the lower boundary of the frequency and stimulation range was fixed while the upper boundary was varied. For the unwarped conditions, only eight to ten channels were needed in both quiet and noise to achieve no significant degradation in speech understanding compared to the normal 12-electrode speech processing. The unwarped conditions were often the best conditions for understanding speech; however, small changes in frequency-to-place mapping (<0.77 octaves for the most basal electrode) yielded no significant degradation in performance from the nearest unwarped condition. A second experiment measured the effect of feedback training for both the unwarped and warped conditions. Improvements were found for the unwarped and frequency-expanded conditions, but not for the compressed condition. These results have implications for new CI processing strategies, such as the inclusion of spectral localization cues.
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Affiliation(s)
- Matthew J Goupell
- Acoustics Research Institute, Austrian Academy of Sciences, Wohllebengasse 12-14, A-1040 Vienna, Austria.
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Başkent D, Edwards B. Simulating listener errors in using genetic algorithms for perceptual optimization. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2007; 121:EL238-43. [PMID: 17552575 DOI: 10.1121/1.2731017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The genetic algorithm (GA) was previously suggested for fitting hearing aid or cochlear implant features by using listener's subjective judgment. In the present study, two human factors that might affect the outcome of the GA when used for perceptual optimization were explored with simulations. Listeners with varying sensitivity in discriminating sentences of different intelligibility and with varying error rates in entering their judgment to the GA were simulated. A comparison of the simulation results with the results from human subjects reported by Başkent et al. Ear Hear. 28(3) 277-289 (2007) showed that these factors could reduce the performance of the GA considerably.
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Affiliation(s)
- Deniz Başkent
- Starkey Hearing Research Center, 2150 Shattuck Ave., Ste. 408, Berkeley, California 94704, USA
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Başkent D, Eiler CL, Edwards B. Using genetic algorithms with subjective input from human subjects: implications for fitting hearing aids and cochlear implants. Ear Hear 2007; 28:370-80. [PMID: 17485986 DOI: 10.1097/aud.0b013e318047935e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To present a comprehensive analysis of the feasibility of genetic algorithms (GA) for finding the best fit of hearing aids or cochlear implants for individual users in clinical or research settings, where the algorithm is solely driven by subjective human input. DESIGN Due to varying pathology, the best settings of an auditory device differ for each user. It is also likely that listening preferences vary at the same time. The settings of a device customized for a particular user can only be evaluated by the user. When optimization algorithms are used for fitting purposes, this situation poses a difficulty for a systematic and quantitative evaluation of the suitability of the fitting parameters produced by the algorithm. In the present study, an artificial listening environment was generated by distorting speech using a noiseband vocoder. The settings produced by the GA for this listening problem could objectively be evaluated by measuring speech recognition and comparing the performance to the best vocoder condition where speech was least distorted. Nine normal-hearing subjects participated in the study. The parameters to be optimized were the number of vocoder channels, the shift between the input frequency range and the synthesis frequency range, and the compression-expansion of the input frequency range over the synthesis frequency range. The subjects listened to pairs of sentences processed with the vocoder, and entered a preference for the sentence with better intelligibility. The GA modified the solutions iteratively according to the subject preferences. The program converged when the user ranked the same set of parameters as the best in three consecutive steps. The results produced by the GA were analyzed for quality by measuring speech intelligibility, for test-retest reliability by running the GA three times with each subject, and for convergence properties. RESULTS Speech recognition scores averaged across subjects were similar for the best vocoder solution and for the solutions produced by the GA. The average number of iterations was 8 and the average convergence time was 25.5 minutes. The settings produced by different GA runs for the same subject were slightly different; however, speech recognition scores measured with these settings were similar. Individual data from subjects showed that in each run, a small number of GA solutions produced poorer speech intelligibility than for the best setting. This was probably a result of the combination of the inherent randomness of the GA, the convergence criterion used in the present study, and possible errors that the users might have made during the paired comparisons. On the other hand, the effect of these errors was probably small compared to the other two factors, as a comparison between subjective preferences and objective measures showed that for many subjects the two were in good agreement. CONCLUSIONS The results showed that the GA was able to produce good solutions by using listener preferences in a relatively short time. For practical applications, the program can be made more robust by running the GA twice or by not using an automatic stopping criterion, and it can be made faster by optimizing the number of the paired comparisons completed in each iteration.
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Affiliation(s)
- Deniz Başkent
- Starkey Hearing Research Center, Berkeley, California 94704, USA.
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