Paired comparisons of nonlinear frequency compression, extended bandwidth, and restricted bandwidth hearing aid processing for children and adults with hearing loss

Effects of Frequency-Composition Algorithm and Phoneme-Based Auditory Training in Older Hearing Aid Users

BACKGROUND AND OBJECTIVES

Frequency-lowering (FL) algorithms improve the audibility of high-frequency sounds by shifting inaudible high-frequency components to audible low-frequency regions. However, the FL algorithm has yielded mixed findings. This study involved two experiments. The first experiment investigated whether objective and subjective auditory outcomes would be enhanced by activating frequency composition (Fcomp), which is a type of FL technique. The second experiment determined whether auditory training with Fcomp activation would provide perceptual benefits to older hearing aid users.

SUBJECTS AND METHODS

Twelve older hearing aid users with moderate to profound high-frequency sensorineural hearing loss participated in this study. In Experiment I, all participants received a 4-week adaptation period to Fcomp before the measurement, and then the influence of Fcomp was evaluated. In Experiment II, among the 12 participants in Experiment I, five received 8-week phoneme-based auditory training while activating Fcomp, whereas the remaining seven did not receive training but continued to use Fcomp as non-trained controls.

RESULTS

In Experiment I, 4-week passive accli-matization period to Fcomp did not improve speech-in-quiet recognition or self-perceived sound quality. In Experiment II, active pho-neme-based training enhanced recognition of consonants and words as well as better speech-quality ratings for trained participants. The consecutive use of Fcomp did not lead to any differences for non-trained participants.

CONCLUSIONS

Overall, phoneme-based auditory training would allow older hearing aid users to relearn frequency-lowered speech sounds and reduce phonetic confusion. However, the analytical training approach did not lead to transfer to sentence recognition or overall satisfaction with the hearing aids.

Validation of an integrated pressure level measured earmold wideband real-ear-to-coupler difference measurement

OBJECTIVE

To validate measurement of predicted earmold wideband real-ear-to-coupler difference (wRECD) using an integrated pressure level (IPL) calibrated transducer and the incorporation of an acoustically measured tubing length correction.

DESIGN

Unilateral earmold SPL wRECD using varied hearing aid tubing length and the proposed predicted earmold IPL wRECD measurement procedure were completed on all participants and compared.

STUDY SAMPLE

22 normal hearing adults with normal middle ear status were recruited.

RESULTS

There were no clinically significant differences between probe-microphone and predicted earmold IPL wRECD measurements between 500 and 2500 Hz. Above 5000 Hz, the predicted earmold IPL wRECD exceeded earmold SPL wRECDs due to lack of standing wave interference. Test-retest reliability of IPL wRECD measurement exceeded the reliability of earmold SPL wRECD measurement across all assessed frequencies, with the greatest improvements in the high frequencies. The acoustically measured tubing length correction largely accounted for acoustic effects of the participant's earmold.

CONCLUSIONS

IPL-based measurements provide a promising alternative to probe-microphone earmold wRECD procedures. Predicted earmold IPL wRECD is measured without probe-microphone placement, agrees well with earmold SPL wRECDs and is expected to extend the valid bandwidth of wRECD measurement.

Validity and reliability of integrated pressure level real-ear-to-coupler difference measurements

OBJECTIVES

(1) To validate the measurement of foam-tip real-ear-to-coupler differences (wRECD) using an integrated pressure level (IPL) method and (2) to compare the reliability of this method to SPL-based measurement of the wRECD.

DESIGN

SPL-based wRECD and the proposed IPL wRECD measurement were completed bilaterally. Test-retest reliability of IPL wRECD was determined with full re-insertion into the ear canal and compared to published SPL wRECD test-retest data.

STUDY SAMPLE

22 adults with normal hearing and middle ear status were recruited.

RESULTS

Differences between SPL-based wRECD and IPL wRECD measurements were within 1.51 dB on average below 5000 Hz. At and above 5000 Hz, IPL wRECD exceeded SPL wRECDs by 6.11 dB on average. The average test-retest difference for IPL wRECD across all assessed frequencies was 0.75 dB with the greatest improvements in reliability found below 750 Hz and above 3000 Hz.

CONCLUSIONS

IPL wRECD yielded improved estimates compared to SPL wRECD in high frequencies, where standing-wave interference is present. Independence from standing wave interference resulted in increased wRECD values above 4000 Hz using the IPL measurement paradigm. IPL wRECD is more reliable than SPL wRECD, does not require precise probe-microphone placement, and provides a wider valid wRECD bandwidth than SPL-based measurement.

Muddy, muddled, or muffled? Understanding the perception of audio quality in music by hearing aid users

Introduction

Previous work on audio quality evaluation has demonstrated a developing convergence of the key perceptual attributes underlying judgments of quality, such as timbral, spatial and technical attributes. However, across existing research there remains a limited understanding of the crucial perceptual attributes that inform audio quality evaluation for people with hearing loss, and those who use hearing aids. This is especially the case with music, given the unique problems it presents in contrast to human speech.

Method

This paper presents a sensory evaluation study utilising descriptive analysis methods, in which a panel of hearing aid users collaborated, through consensus, to identify the most important perceptual attributes of music audio quality and developed a series of rating scales for future listening tests. Participants (N = 12), with a hearing loss ranging from mild to severe, first completed an online elicitation task, providing single-word terms to describe the audio quality of original and processed music samples; this was completed twice by each participant, once with hearing aids, and once without. Participants were then guided in discussing these raw terms across three focus groups, in which they reduced the term space, identified important perceptual groupings of terms, and developed perceptual attributes from these groups (including rating scales and definitions for each).

Results

Findings show that there were seven key perceptual dimensions underlying music audio quality (clarity, harshness, distortion, spaciousness, treble strength, middle strength, and bass strength), alongside a music audio quality attribute and possible alternative frequency balance attributes.

Discussion

We outline how these perceptual attributes align with extant literature, how attribute rating instruments might be used in future work, and the importance of better understanding the music listening difficulties of people with varied profiles of hearing loss.

Perceived Sound Quality of Hearing Aids With Varying Placements of Microphone and Receiver

PURPOSE

Perceived sound quality was variously compared between either no aiding or aiding with three models of hearing aid that varied the microphone position around the pinna, depth of the receiver in the auditory meatus, degree of meatal occlusion, and processing sophistication. The hearing aids were modern designs and commercially available at the time of testing.

METHOD

Binaural recordings of multichannel spatially separated speech and music excerpts were made in a manikin, either open ear or aided. Recordings were presented offline over wide-bandwidth, high-quality insert earphones. Participants listened to pairs of the recordings and made preference ratings both by clarity and externality (a proxy for "spaciousness"). Two separate groups of adults were tested, 20 with audiometrically normal hearing (NH) and 20 with mild-to-moderate sensorineural hearing loss (hearing impaired [HI]).

RESULTS

For ratings of speech clarity, the NH group expressed no preference between the open ear and a deeply inserted occluding aid, both of which were preferred to a low-pass filtered output of the same aid. For the music signal, a small preference emerged for the open-ear recording over that of the aid. For the HI group, clarity of the deeply inserted aid was similar to in-the-ear and behind-the-ear devices for speech, but worse for music. Ratings of spaciousness produced no clear result in either group, which can be attributed to study limitations and/or participant factors.

CONCLUSION

Based on clarity, a wide bandwidth, particularly to beyond 5 kHz generally and below 300 Hz for music, is desirable, independent of hearing aid design.

The Importance of High-Frequency Bandwidth on Speech and Language Development in Children: A Review of Patricia Stelmachowicz's Contributions to Pediatric Audiology

We review the literature related to Patricia Stelmachowicz's research in pediatric audiology, specifically focusing on the influence of audibility in language development and acquisition of linguistic rules. Pat Stelmachowicz spent her career increasing our awareness and understanding of children with mild to severe hearing loss who use hearing aids. Using a variety of novel experiments and stimuli, Pat and her colleagues produced a robust body of evidence to support the hypothesis that development moderates the role of frequency bandwidth on speech perception, particularly for fricative sounds. The prolific research that came out of Pat's lab had several important implications for clinical practice. First, her work highlighted that children require access to more high-frequency speech information than adults in the detection and identification of fricatives such as /s/ and /z/. These high-frequency speech sounds are important for morphological and phonological development. Consequently, the limited bandwidth of conventional hearing aids may delay the formation of linguistic rules in these two domains for children with hearing loss. Second, it emphasized the importance of not merely applying adult findings to the clinical decision-making process in pediatric amplification. Clinicians should use evidence-based practices to verify and provide maximum audibility for children who use hearing aids to acquire spoken language.

Factors Affecting the Accessibility of Voice Telephony for People with Hearing Loss: Audio Encoding, Network Impairments, Video and Environmental Noise

This paper describes four studies with a total of 114 individuals with hearing loss and 12 hearing controls that investigate the impact of audio quality parameters on voice telecommunications. These studies were first informed by a survey of 439 individuals with hearing loss on their voice telecommunications experiences. While voice telephony was very important, with high usage of wireless mobile phones, respondents reported relatively low satisfaction with their hearing devices’ performance for telephone listening, noting that improved telephone audio quality was a significant need. The studies cover three categories of audio quality parameters: (1) narrowband (NB) versus wideband (WB) audio; (2) encoding audio at varying bit rates, from typical rates used in today's mobile networks to the highest quality supported by these audio codecs; and (3) absence of packet loss to worst-case packet loss in both mobile and VoIP networks. Additionally, NB versus WB audio was tested in auditory-only and audiovisual presentation modes and in quiet and noisy environments. With WB audio in a quiet environment, individuals with hearing loss exhibited better speech recognition, expended less perceived mental effort, and rated speech quality higher than with NB audio. WB audio provided a greater benefit when listening alone than when the visual channel also was available. The noisy environment significantly degraded performance for both presentation modes, but particularly for listening alone. Bit rate affected speech recognition for NB audio, and speech quality ratings for both NB and WB audio. Packet loss affected all of speech recognition, mental effort, and speech quality ratings. WB versus NB audio also affected hearing individuals, especially under packet loss. These results are discussed in terms of the practical steps they suggest for the implementation of telecommunications systems and related technical standards and policy considerations to improve the accessibility of voice telephony for people with hearing loss.

Audibility and Spectral-Ripple Discrimination Thresholds as Predictors of Word Recognition with Nonlinear Frequency Compression

BACKGROUND

Nonlinear frequency compression (NFC) lowers high-frequency sounds to a lower frequency and is used to improve high-frequency audibility. However, the efficacy of NFC varies widely-while some individuals benefit from NFC, many do not. Spectral resolution is one factor that might explain individual benefit from NFC. Because individuals with better spectral resolution understand more speech than those with poorer spectral resolution, it was hypothesized that individual benefit from NFC could be predicted from the change in spectral resolution measured with NFC relative to a condition without NFC.

PURPOSE

This study aimed to determine the impact of NFC on access to spectral information and whether these changes predict individual benefit from NFC for adults with sensorineural hearing loss (SNHL).

RESEARCH DESIGN

Present study is a quasi-experimental cohort study. Participants used a pair of hearing aids set to the Desired Sensation Level algorithm (DSL m[i/o]).

STUDY SAMPLE

Participants were 19 adults with SNHL, recruited from the Boys Town National Research Hospital Participant Registry.

DATA COLLECTION AND ANALYSIS

Participants were seated in a sound-attenuating booth and then percent-correct recognition of words, and spectral-ripple discrimination thresholds were measured for two different conditions, with and without NFC. Because audibility is known to influence spectral-ripple thresholds and benefit from NFC, audibility was quantified using the aided speech intelligibility index (SII). Linear mixed models were generated to predict word recognition using the aided SII and spectral-ripple discrimination thresholds.

RESULTS

While NFC did not influence percent-correct word recognition, participants with higher (better) aided SII and spectral-ripple discrimination thresholds understood more words than those with either a lower aided SII or spectral-ripple discrimination threshold. Benefit from NFC was not predictable from a participant's aided SII or spectral-ripple discrimination threshold.

CONCLUSION

We have extended previous work on the effect of audibility on benefit from NFC to include a measure of spectral resolution, the spectral-ripple discrimination threshold. Clinically, these results suggest that patients with better audibility and spectral resolution will understand speech better than those with poorer audibility or spectral resolution; however, these results are inconsistent with the notion that individual benefit from NFC is predictable from aided audibility or spectral resolution.

Effects of Adaptive Non-linear Frequency Compression in Hearing Aids on Mandarin Speech and Sound-Quality Perception

Objective

This study was aimed at examining the effects of an adaptive non-linear frequency compression algorithm implemented in hearing aids (i.e., SoundRecover2, or SR2) at different parameter settings and auditory acclimatization on speech and sound-quality perception in native Mandarin-speaking adult listeners with sensorineural hearing loss.

Design

Data consisted of participants’ unaided and aided hearing thresholds, Mandarin consonant and vowel recognition in quiet, and sentence recognition in noise, as well as sound-quality ratings through five sessions in a 12-week period with three SR2 settings (i.e., SR2 off, SR2 default, and SR2 strong).

Study Sample

Twenty-nine native Mandarin-speaking adults aged 37–76 years old with symmetric sloping moderate-to-profound sensorineural hearing loss were recruited. They were all fitted bilaterally with Phonak Naida V90-SP BTE hearing aids with hard ear-molds.

Results

The participants demonstrated a significant improvement of aided hearing in detecting high frequency sounds at 8 kHz. For consonant recognition and overall sound-quality rating, the participants performed significantly better with the SR2 default setting than the other two settings. No significant differences were found in vowel and sentence recognition among the three SR2 settings. Test session was a significant factor that contributed to the participants’ performance in all speech and sound-quality perception tests. Specifically, the participants benefited from a longer duration of hearing aid use.

Conclusion

Findings from this study suggested possible perceptual benefit from the adaptive non-linear frequency compression algorithm for native Mandarin-speaking adults with moderate-to-profound hearing loss. Periods of acclimatization should be taken for better performance in novel technologies in hearing aids.

Changes in Orientation Behavior due to Extended High-Frequency (5 to 10 kHz) Spatial Cues

OBJECTIVES

Current hearing aids have a limited bandwidth, which limits the intelligibility and quality of their output, and inhibits their uptake. Recent advances in signal processing, as well as novel methods of transduction, allow for a greater useable frequency range. Previous studies have shown a benefit for this extended bandwidth in consonant recognition, talker-sex identification, and separating sound sources. To explore whether there would be any direct spatial benefits to extending bandwidth, we used a dynamic localization method in a realistic situation.

DESIGN

Twenty-eight adult participants with minimal hearing loss reoriented themselves as quickly and accurately as comfortable to a new, off-axis near-field talker continuing a story in a background of far-field talkers of the same overall level in a simulated large room with common building materials. All stimuli were low-pass filtered at either 5 or 10 kHz on each trial. To further simulate current hearing aids, participants wore microphones above the pinnae and insert earphones adjusted to provide a linear, zero-gain response.

RESULTS

Each individual trajectory was recorded with infra-red motion-tracking and analyzed for accuracy, duration, start time, peak velocity, peak velocity time, complexity, reversals, and misorientations. Results across listeners showed a significant increase in peak velocity and significant decrease in start and peak velocity time with greater (10 kHz) bandwidth.

CONCLUSIONS

These earlier, swifter orientations demonstrate spatial benefits beyond static localization accuracy in plausible conditions; extended bandwidth without pinna cues provided more salient cues in a realistic mixture of talkers.

Detection, Speech Recognition, Loudness, and Preference Outcomes With a Direct Drive Hearing Aid: Effects of Bandwidth

Direct drive hearing devices, which deliver a signal directly to the middle ear by vibrating the tympanic membrane via a lens placed in contact with the umbo, are designed to provide an extension of audible bandwidth, but there are few studies of the effects of these devices on preference, speech intelligibility, and loudness. The current study is the first to compare aided speech understanding between narrow and extended bandwidth conditions for listeners with hearing loss while fitted with a direct drive hearing aid system. The study also explored the effect of bandwidth on loudness perception and investigated subjective preference for bandwidth. Fifteen adult hearing aid users with symmetrical sensorineural hearing loss participated in a prospective, within-subjects, randomized single-blind repeated-measures study. Participants wore the direct drive hearing aids for 4 to 15 weeks (average 6 weeks) prior to outcome measurement. Outcome measures were completed in various bandwidth conditions achieved by reducing the gain of the device above 5000 Hz or by filtering the stimuli. Aided detection thresholds provided evidence of amplification to 10000 Hz. A significant improvement was found in high-frequency consonant detection and recognition, as well as for speech in noise performance in the full versus narrow bandwidth conditions. Subjective loudness ratings increased with provision of the full bandwidth available; however, real-world trials showed most participants were able to wear the full bandwidth hearing aids with only small adjustments to the prescription method. The majority of participants had either no preference or a preference for the full bandwidth setting.

Individual Differences Offer Insight Into Clinical Recommendations for Directional and Remote Microphone Technology Use in Children

Purpose This study sought to evaluate the effects of common hearing aid microphone technologies on speech recognition and listening effort, and to evaluate potential predictive factors related to microphone benefits for school-age children with hearing loss in a realistic listening situation. Method Children (n = 17, ages 10-17 years) with bilateral, sensorineural hearing loss were fitted with hearing aids set to include three programs: omnidirectional, adaptive directional, and omnidirectional + remote microphone. Children completed a dual-task paradigm in a moderately reverberant room. The primary task included monosyllabic word recognition, with target speech presented at 60 dB A from 0° (front) or 180° (back) azimuth. The secondary task was a "go/no-go," visual shape-recognition task. Multitalker babble noise created a +5 dB SNR. Children were evaluated in two speaker conditions (front, back) using all three hearing aid programs. The remote microphone transmitter remained at the front speaker throughout testing. Speech recognition performance was calculated from the primary task while listening effort was measured as response time during the secondary task. Results Speech presented from the back significantly increased listening effort and caused a reduction in speech perception when directional and remote microphones were used. Considerable variability was found in pattern of benefit across microphones and source location. Clinical measures did not predict benefit patterns with directional or remote microphones; however, child age and performance with omnidirectional microphones did. Conclusions When compared to a traditional omnidirectional setting, the directional and remote microphone configurations evaluated in this study have the potential to provide benefit for some children and increase difficulty for others when used in dynamic environments. A child's performance with omnidirectional hearing aids could be used to better inform clinical recommendations for these technologies.

Perceptual Benefits of Extended Bandwidth Hearing Aids With Children: A Within-Subject Design Using Clinically Available Hearing Aids

Purpose The aim of the study was to investigate the achieved audibility with clinically available, modern, high-end, behind-the-ear hearing aids fitted using the Desired Sensation Level v5.0 child prescription for a clinical sample of children with hearing impairment and the effect of the extended bandwidth provided by the hearing aids on several outcome measures. Method The achieved audibility was measured using the maximum audible output frequency method. Twenty-eight children (7-17 years old) with mild to severe hearing losses completed this study. Two hearing aid conditions were fitted for each participant: an extended bandwidth condition, which was fitted to targets as closely as possible, and a restricted bandwidth condition, for which aided output was restricted above 4.5 kHz. Consonant discrimination in noise, subjective preference, aided loudness growth, and preferred listening levels were evaluated in both conditions. Results The extended bandwidth hearing aid fittings provided speech audibility above 4.5 kHz for all children, with an average maximum audible output frequency of 7376 Hz (SD = 1669 Hz). When compared to a restricted bandwidth, the extended bandwidth condition led to an improvement of 5.4% for consonant discrimination in noise scores, mostly attributable to /s/, /z/, and /t/ phoneme perception. Aided loudness results and preferred listening levels were not significantly different across bandwidth conditions; however, 65% of the children indicated a subjective preference for the extended bandwidth. Conclusion The study suggests that providing the full bandwidth available, with modern, behind-the-ear hearing aids, leads to improved audibility, when compared to restricted bandwidth hearing aids, and that it leads to beneficial outcomes for children who use hearing aids, fitted to the Desired Sensation Level v5.0 child prescription, without causing significant increases in their loudness perception.

Effects of nonlinear frequency compression on Mandarin speech and sound-quality perception in hearing-aid users

Objective: The purpose of the present study was to examine the effects of NLFC fitting in hearing aids and auditory acclimatisation on speech perception and sound-quality rating in hearing-impaired, native Mandarin-speaking adult listeners.Design: Mandarin consonant, vowel and tone recognition were tested in quiet and sentence recognition in noise (speech-shaped noise at a +5 dB signal-to-noise ratio) with NLFC-on and NLFC-off. Sound-quality ratings were collected on a 0-10 scale at each test session. A generalised linear model and correlational analyses were performed.Study sample: Thirty native Mandarin-speaking adults with moderate-to-severe sensorineural hearing loss were recruited.Results: The hearing-impaired listeners showed significantly higher accuracy with NLFC-on than with NLFC-off for consonant and sentence recognition and the recognition performance improved with both NLFC-on and off as a function of increased length of use. The satisfaction score of sound-quality ratings for different types of sounds significantly increased with NLFC-on than with NLFC-off. The speech recognition results showed moderate to strong correlation with the unaided hearing thresholds.Conclusion: For native Mandarin-speaking listeners with hearing loss, the NLFC technology provided modest but significant improvement in Mandarin fricative and sentence recognition. Subjectively, the naturalness and overall preference of sound-quality satisfaction judgement also improved with NLFC.

Speech Perception and Sound-Quality Rating with an Adaptive Nonlinear Frequency Compression Algorithm in Mandarin-Speaking Hearing Aid Users

BACKGROUND

Mandarin Chinese has a rich repertoire of high-frequency speech sounds. This may pose a remarkable challenge to hearing-impaired listeners who speak Mandarin Chinese because of their high-frequency sloping hearing loss. An adaptive nonlinear frequency compression (adaptive NLFC) algorithm has been implemented in contemporary hearing aids to alleviate the problem.

PURPOSE

The present study examined the performance of speech perception and sound-quality rating in Mandarin-speaking hearing-impaired listeners using hearing aids fitted with adaptive NLFC (i.e., SoundRecover2 or SR2) at different parameter settings.

RESEARCH DESIGN

Hearing-impaired listeners' phoneme detection thresholds, speech reception thresholds, and sound-quality ratings were collected with various SR2 settings.

STUDY SAMPLE

The participants included 15 Mandarin-speaking adults aged 32 to 84 years old who had symmetric sloping severe-to-profound sensorineural hearing loss.

INTERVENTION

The participants were fitted bilaterally with Phonak Naida V90-SP hearing aids.

DATA COLLECTION AND ANALYSIS

The outcome measures included phoneme detection threshold using the Mandarin Phonak Phoneme Perception test, speech reception threshold using the Mandarin hearing in noise test (M-HINT), and sound-quality ratings on human speech in quiet and noise, bird chirps, and music in quiet. For each test, five experimental settings were applied and compared: SR2-off, SR2-weak, SR2-default, SR2-strong 1, and SR2-strong 2.

RESULTS

The results showed that listeners performed significantly better with SR2-strong 1 and SR2-strong 2 settings than with SR2-off or SR2-weak settings for speech reception threshold and phoneme detection threshold. However, no significant improvement was observed in sound-quality ratings among different settings.

CONCLUSIONS

These preliminary findings suggested that the adaptive NLFC algorithm provides perceptual benefit to Mandarin-speaking people with severe-to-profound hearing loss.

Speech recognition, loudness, and preference with extended bandwidth hearing aids for adult hearing aid users

Objective: In contrast to the past, some current hearing aids can provide gain for frequencies above 4-5 kHz. This study assessed the effect of wider bandwidth on outcome measures using hearing aids fitted with the DSL v5.0 prescription.Design: There were two conditions: an extended bandwidth condition, for which the maximum available bandwidth was provided, and a restricted bandwidth condition, in which gain was reduced for frequencies above 4.5 kHz. Outcome measures were assessed in both conditions.Study sample: Twenty-four participants with mild-to-moderately-severe sensorineural high-frequency sloping hearing loss.Results: Providing extended bandwidth resulted in maximum audible output frequency values of 7.5 kHz on average for an input level of 65 dB SPL. An improvement in consonant discrimination scores (4.1%), attributable to better perception of /s/, /z/, and /t/ phonemes, was found in the extended bandwidth condition, but no significant change in loudness perception or preferred listening levels was found. Most listeners (79%) had either no preference (33%) or some preference for the extended bandwidth condition (46%).Conclusions: The results suggest that providing the maximum bandwidth available with modern hearing aids fitted with DSL v5.0, using targets from 0.25 to 8 kHz, can be beneficial for the tested population.

Comparison of Frequency Transposition and Frequency Compression for People With Extensive Dead Regions in the Cochlea

The objective was to determine the effects of two frequency-lowering algorithms (frequency transposition, FT, and frequency compression, FC) on audibility, speech identification, and subjective benefit, for people with high-frequency hearing loss and extensive dead regions (DRs) in the cochlea. A single-blind randomized crossover design was used. FT and FC were compared with each other and with a control condition (denoted ‘Control’) without frequency lowering, using hearing aids that were otherwise identical. Data were collected after at least 6 weeks of experience with a condition. Outcome measures were audibility, scores for consonant identification, scores for word-final /s, z/ detection (S test), sentence-in-noise intelligibility, and a questionnaire assessing self-perceived benefit (Spatial and Qualities of Hearing Scale). Ten adults with steeply sloping high-frequency hearing loss and extensive DRs were tested. FT and FC improved the audibility of some high-frequency sounds for 7 and 9 participants out of 10, respectively. At the group level, performance for FT and FC did not differ significantly from that for Control for any of the outcome measures. However, the pattern of consonant confusions varied across conditions. Bayesian analysis of the confusion matrices revealed a trend for FT to lead to more consistent error patterns than FC and Control. Thus, FT may have the potential to give greater benefit than Control or FC following extended experience or training.

The S-SH Confusion Test and the Effects of Frequency Lowering

Purpose Frequency lowering in hearing aids can cause listeners to perceive [s] as [ʃ]. The S-SH Confusion Test, which consists of 66 minimal word pairs spoken by 6 female talkers, was designed to help clinicians and researchers document these negative side effects. This study's purpose was to use this new test to evaluate the hypothesis that these confusions will increase to the extent that low frequencies are altered. Method Twenty-one listeners with normal hearing were each tested on 7 conditions. Three were control conditions that were low-pass filtered at 3.3, 5.0, and 9.1 kHz. Four conditions were processed with nonlinear frequency compression (NFC): 2 had a 3.3-kHz maximum audible output frequency (MAOF), with a start frequency (SF) of 1.6 or 2.2 kHz; 2 had a 5.0-kHz MAOF, with an SF of 1.6 or 4.0 kHz. Listeners' responses were analyzed using concepts from signal detection theory. Response times were also collected as a measure of cognitive processing. Results Overall, [s] for [ʃ] confusions were minimal. As predicted, [ʃ] for [s] confusions increased for NFC conditions with a lower versus higher MAOF and with a lower versus higher SF. Response times for trials with correct [s] responses were shortest for the 9.1-kHz control and increased for the 5.0- and 3.3-kHz controls. NFC response times were also significantly longer as MAOF and SF decreased. The NFC condition with the highest MAOF and SF had statistically shorter response times than its control condition, indicating that, under some circumstances, NFC may ease cognitive processing. Conclusions Large differences in the S-SH Confusion Test across frequency-lowering conditions show that it can be used to document a major negative side effect associated with frequency lowering. Smaller but significant differences in response times for correct [s] trials indicate that NFC can help or hinder cognitive processing, depending on its settings.

Effects of Amplification and Hearing Aid Experience on the Contribution of Specific Frequency Bands to Loudness

OBJECTIVES

The primary aim of this study is to describe the effect of hearing aid amplification on the contribution of specific frequency bands to overall loudness in adult listeners with sensorineural hearing loss (SNHL). Results for listeners with SNHL were compared with results for listeners with normal hearing (NH) to evaluate whether amplification restores the normal perception of loudness for broadband sound. A secondary aim of this study is to determine whether the loudness perception of new hearing aid users becomes closer to normal over the first few months of hearing aid use. It was hypothesized that amplification would cause the high-frequency bands to contribute most to the perception of loudness and that this effect might decrease as new hearing aid users adapt to amplification.

DESIGN

In experiment 1, 8 adult listeners with SNHL completed a two-interval forced-choice loudness task in unaided and aided conditions. A control group of 7 listeners with NH completed the task in the unaided condition only. Stimuli were composed of seven summed noise bands whose levels were independently adjusted between presentations. During a trial, two stimuli were presented, and listeners determined the louder one. The correlation between the difference in levels for a given noise band on every trial and the listener's response was calculated. The resulting measure is termed the perceptual weight because it provides an estimate of the relative contribution of a given frequency region to overall loudness. In experiment 2, a separate group of 6 new hearing aid users repeated identical procedures on 2 sessions separated by 12 weeks.

RESULTS

Results for listeners with SNHL were similar in experiments 1 and 2. In the unaided condition, perceptual weights were greatest for the low-frequency bands. In the aided condition, perceptual weights were greatest for the high-frequency bands. On average, the aided perceptual weights for listeners with SNHL for high-frequency bands were greater than the unaided weights for listeners with NH. In experiment 2, hearing aid experience did not have a significant effect on perceptual weights.

CONCLUSIONS

The high frequencies seem to dominate loudness perception in listeners with SNHL using hearing aids as they do in listeners with NH. However, the results suggest that amplification causes high frequencies to have a larger contribution to overall loudness compared with listeners with NH. The contribution of the high frequencies to loudness did not change after an acclimatization period for the first-time hearing aid users.

Speech Perception in Noise and Listening Effort of Older Adults With Nonlinear Frequency Compression Hearing Aids

OBJECTIVES

The purpose of this laboratory-based study was to compare the efficacy of two hearing aid fittings with and without nonlinear frequency compression, implemented within commercially available hearing aids. Previous research regarding the utility of nonlinear frequency compression has revealed conflicting results for speech recognition, marked by high individual variability. Individual differences in auditory function and cognitive abilities, specifically hearing loss slope and working memory, may contribute to aided performance. The first aim of the study was to determine the effect of nonlinear frequency compression on aided speech recognition in noise and listening effort using a dual-task test paradigm. The hypothesis, based on the Ease of Language Understanding model, was that nonlinear frequency compression would improve speech recognition in noise and decrease listening effort. The second aim of the study was to determine if listener variables of hearing loss slope, working memory capacity, and age would predict performance with nonlinear frequency compression.

DESIGN

A total of 17 adults (age, 57-85 years) with symmetrical sensorineural hearing loss were tested in the sound field using hearing aids fit to target (NAL-NL2). Participants were recruited with a range of hearing loss severities and slopes. A within-subjects, single-blinded design was used to compare performance with and without nonlinear frequency compression. Speech recognition in noise and listening effort were measured by adapting the Revised Speech in Noise Test into a dual-task paradigm. Participants were required trial-by-trial to repeat the last word of each sentence presented in speech babble and then recall the sentence-ending words after every block of six sentences. Half of the sentences were rich in context for the recognition of the final word of each sentence, and half were neutral in context. Extrinsic factors of sentence context and nonlinear frequency compression were manipulated, and intrinsic factors of hearing loss slope, working memory capacity, and age were measured to determine which participant factors were associated with benefit from nonlinear frequency compression.

RESULTS

On average, speech recognition in noise performance significantly improved with the use of nonlinear frequency compression. Individuals with steeply sloping hearing loss received more recognition benefit. Recall performance also significantly improved at the group level, with nonlinear frequency compression revealing reduced listening effort. The older participants within the study cohort received less recall benefit than the younger participants. The benefits of nonlinear frequency compression for speech recognition and listening effort did not correlate with each other, suggesting separable sources of benefit for these outcome measures.

CONCLUSIONS

Improvements of speech recognition in noise and reduced listening effort indicate that adult hearing aid users can receive benefit from nonlinear frequency compression in a noisy environment, with the amount of benefit varying across individuals and across outcome measures. Evidence supports individualized selection of nonlinear frequency compression, with results suggesting benefits in speech recognition for individuals with steeply sloping hearing losses and in listening effort for younger individuals. Future research is indicated with a larger data set on the dual-task paradigm as a potential cognitive outcome measure.

Word Recognition and Learning: Effects of Hearing Loss and Amplification Feature

Two amplification features were examined using auditory tasks that varied in stimulus familiarity. It was expected that the benefits of certain amplification features would increase as the familiarity with the stimuli decreased. A total of 20 children and 15 adults with normal hearing as well as 21 children and 17 adults with mild to severe hearing loss participated. Three models of ear-level devices were selected based on the quality of the high-frequency amplification or the digital noise reduction (DNR) they provided. The devices were fitted to each participant and used during testing only. Participants completed three tasks: (a) word recognition, (b) repetition and lexical decision of real and nonsense words, and (c) novel word learning. Performance improved significantly with amplification for both the children and the adults with hearing loss. Performance improved further with wideband amplification for the children more than for the adults. In steady-state noise and multitalker babble, performance decreased for both groups with little to no benefit from amplification or from the use of DNR. When compared with the listeners with normal hearing, significantly poorer performance was observed for both the children and adults with hearing loss on all tasks with few exceptions. Finally, analysis of across-task performance confirmed the hypothesis that benefit increased as the familiarity of the stimuli decreased for wideband amplification but not for DNR. However, users who prefer DNR for listening comfort are not likely to jeopardize their ability to detect and learn new information when using this feature.

A Set of Time-and-Frequency-Localized Short-Duration Speech-Like Stimuli for Assessing Hearing-Aid Performance via Cortical Auditory-Evoked Potentials

Short-duration speech-like stimuli, for example, excised from running speech, can be used in the clinical setting to assess the integrity of the human auditory pathway at the level of the cortex. Modeling of the cochlear response to these stimuli demonstrated an imprecision in the location of the spectrotemporal energy, giving rise to uncertainty as to what and when of a stimulus caused any evoked electrophysiological response. This article reports the development and assessment of four short-duration, limited-bandwidth stimuli centered at low, mid, mid-high, and high frequencies, suitable for free-field delivery and, in addition, reproduction via hearing aids. The durations were determined by the British Society of Audiology recommended procedure for measuring Cortical Auditory-Evoked Potentials. The levels and bandwidths were chosen via a computational model to produce uniform cochlear excitation over a width exceeding that likely in a worst-case hearing-impaired listener. These parameters produce robustness against errors in insertion gains, and variation in frequency responses, due to transducer imperfections, room modes, and age-related variation in meatal resonances. The parameter choice predicts large spectral separation between adjacent stimuli on the cochlea. Analysis of the signals processed by examples of recent digital hearing aids mostly show similar levels of gain applied to each stimulus, independent of whether the stimulus was presented in isolation, bursts, continuous, or embedded in continuous speech. These stimuli seem to be suitable for measuring hearing-aided Cortical Auditory-Evoked Potentials and have the potential to be of benefit in the clinical setting.

The Use of Frequency Lowering Technology in the Treatment of Severe-to-Profound Hearing Loss: A Review of the Literature and Candidacy Considerations for Clinical Application

This article provides a review of the current literature on the topic of frequency lowering hearing aid technology specific to the treatment of severe and profound levels of hearing impairment in child and adult listeners. Factors to consider when assessing listener candidacy for frequency lowering technology are discussed. These include factors related to audiometric assessment, the listener, the type of hearing aid technology, and the verification and validation procedures that can assist in determining candidacy for frequency lowering technology. An individualized candidacy assessment including the use of real-ear verification measures and carefully chosen validation tools are recommended for listeners requiring greater audibility of high-frequency sounds, when compared with amplification via conventional hearing aid technology.

Listener Performance with a Novel Hearing Aid Frequency Lowering Technique

BACKGROUND

Sloping hearing loss imposes limits on audibility for high-frequency sounds in many hearing aid users. Signal processing algorithms that shift high-frequency sounds to lower frequencies have been introduced in hearing aids to address this challenge by improving audibility of high-frequency sounds.

PURPOSE

This study examined speech perception performance, listening effort, and subjective sound quality ratings with conventional hearing aid processing and a new frequency-lowering signal processing strategy called frequency composition (FC) in adults and children.

RESEARCH DESIGN

Participants wore the study hearing aids in two signal processing conditions (conventional processing versus FC) at an initial laboratory visit and subsequently at home during two approximately six-week long trials, with the order of conditions counterbalanced across individuals in a double-blind paradigm.

STUDY SAMPLE

Children (N = 12, 7 females, mean age in years = 12.0, SD = 3.0) and adults (N = 12, 6 females, mean age in years = 56.2, SD = 17.6) with bilateral sensorineural hearing loss who were full-time hearing aid users.

DATA COLLECTION AND ANALYSES

Individual performance with each type of processing was assessed using speech perception tasks, a measure of listening effort, and subjective sound quality surveys at an initial visit. At the conclusion of each subsequent at-home trial, participants were retested in the laboratory. Linear mixed effects analyses were completed for each outcome measure with signal processing condition, age group, visit (prehome versus posthome trial), and measures of aided audibility as predictors.

RESULTS

Overall, there were few significant differences in speech perception, listening effort, or subjective sound quality between FC and conventional processing, effects of listener age, or longitudinal changes in performance. Listeners preferred FC to conventional processing on one of six subjective sound quality metrics. Better speech perception performance was consistently related to higher aided audibility.

CONCLUSIONS

These results indicate that when high-frequency speech sounds are made audible with conventional processing, speech recognition ability and listening effort are similar between conventional processing and FC. Despite the lack of benefit to speech perception, some listeners still preferred FC, suggesting that qualitative measures should be considered when evaluating candidacy for this signal processing strategy.

Listening Effort and Speech Recognition with Frequency Compression Amplification for Children and Adults with Hearing Loss

BACKGROUND

Nonlinear frequency compression (NFC) can improve the audibility of high-frequency sounds by lowering them to a frequency where audibility is better; however, this lowering results in spectral distortion. Consequently, performance is a combination of the effects of increased access to high-frequency sounds and the detrimental effects of spectral distortion. Previous work has demonstrated positive benefits of NFC on speech recognition when NFC is set to improve audibility while minimizing distortion. However, the extent to which NFC impacts listening effort is not well understood, especially for children with sensorineural hearing loss (SNHL).

PURPOSE

To examine the impact of NFC on recognition and listening effort for speech in adults and children with SNHL.

RESEARCH DESIGN

Within-subject, quasi-experimental study. Participants listened to amplified nonsense words that were (1) frequency-lowered using NFC, (2) low-pass filtered at 5 kHz to simulate the restricted bandwidth (RBW) of conventional hearing aid processing, or (3) low-pass filtered at 10 kHz to simulate extended bandwidth (EBW) amplification.

STUDY SAMPLE

Fourteen children (8-16 yr) and 14 adults (19-65 yr) with mild-to-severe SNHL.

INTERVENTION

Participants listened to speech processed by a hearing aid simulator that amplified input signals to fit a prescriptive target fitting procedure.

DATA COLLECTION AND ANALYSIS

Participants were blinded to the type of processing. Participants' responses to each nonsense word were analyzed for accuracy and verbal-response time (VRT; listening effort). A multivariate analysis of variance and linear mixed model were used to determine the effect of hearing-aid signal processing on nonsense word recognition and VRT.

RESULTS

Both children and adults identified the nonsense words and initial consonants better with EBW and NFC than with RBW. The type of processing did not affect the identification of the vowels or final consonants. There was no effect of age on recognition of the nonsense words, initial consonants, medial vowels, or final consonants. VRT did not change significantly with the type of processing or age.

CONCLUSION

Both adults and children demonstrated improved speech recognition with access to the high-frequency sounds in speech. Listening effort as measured by VRT was not affected by access to high-frequency sounds.

Effect of Context and Hearing Loss on Time-Gated Word Recognition in Children

OBJECTIVES

The purpose of this study was to examine word recognition in children who are hard of hearing (CHH) and children with normal hearing (CNH) in response to time-gated words presented in high- versus low-predictability sentences (HP, LP), where semantic cues were manipulated. Findings inform our understanding of how CHH combine cognitive-linguistic and acoustic-phonetic cues to support spoken word recognition. It was hypothesized that both groups of children would be able to make use of linguistic cues provided by HP sentences to support word recognition. CHH were expected to require greater acoustic information (more gates) than CNH to correctly identify words in the LP condition. In addition, it was hypothesized that error patterns would differ across groups.

DESIGN

Sixteen CHH with mild to moderate hearing loss and 16 age-matched CNH participated (5 to 12 years). Test stimuli included 15 LP and 15 HP age-appropriate sentences. The final word of each sentence was divided into segments and recombined with the sentence frame to create series of sentences in which the final word was progressively longer by the gated increments. Stimuli were presented monaurally through headphones and children were asked to identify the target word at each successive gate. They also were asked to rate their confidence in their word choice using a five- or three-point scale. For CHH, the signals were processed through a hearing aid simulator. Standardized language measures were used to assess the contribution of linguistic skills.

RESULTS

Analysis of language measures revealed that the CNH and CHH performed within the average range on language abilities. Both groups correctly recognized a significantly higher percentage of words in the HP condition than in the LP condition. Although CHH performed comparably with CNH in terms of successfully recognizing the majority of words, differences were observed in the amount of acoustic-phonetic information needed to achieve accurate word recognition. CHH needed more gates than CNH to identify words in the LP condition. CNH were significantly lower in rating their confidence in the LP condition than in the HP condition. CHH, however, were not significantly different in confidence between the conditions. Error patterns for incorrect word responses across gates and predictability varied depending on hearing status.

CONCLUSIONS

The results of this study suggest that CHH with age-appropriate language abilities took advantage of context cues in the HP sentences to guide word recognition in a manner similar to CNH. However, in the LP condition, they required more acoustic information (more gates) than CNH for word recognition. Differences in the structure of incorrect word responses and their nomination patterns across gates for CHH compared with their peers with NH suggest variations in how these groups use limited acoustic information to select word candidates.

Is non-linear frequency compression amplification beneficial to adults and children with hearing loss? A systematic review

OBJECTIVE

To conduct a systematic review of the benefits of non-linear frequency compression (NLFC) in adults and children.

DESIGN

Ten databases were searched for studies comparing the effects of NLFC and conventional processing (CP) for the period January 2008 to September 2017.

STUDY SAMPLE

Twelve articles were included in this review: four adults and school-aged only, one pre-school only and three with both adults and school-aged children.

RESULTS

A two-stage process was implemented to grade the evidence. The individual studies were graded based on their study type (from 1 = highest quality of evidence to 5 = the lowest quality) and then sub-graded based on their quality ("a" for "good quality" or "b" for "lesser quality"). All studies were awarded 4a, except the single pre-school study, which was awarded 2a. The overall evidence for each population was graded based on the quality, quantity and consistency of the studies. The body of evidence was rated as very low for both adults and school-aged children, but high for pre-school children.

CONCLUSION

The low number (and quality) of studies means that evidence supporting the benefit from NLFC is inconclusive. Further high-quality RCTs are required to provide a conclusive answer to this question.

Preliminary evaluation of a novel non-linear frequency compression scheme for use in children

OBJECTIVE

The primary goal of this study was to evaluate a new form of non-linear frequency compression (NLFC) in children. The new NLFC processing scheme is adaptive and potentially allows for a better preservation of the spectral characteristics of the input sounds when compared to conventional NLFC processing.

DESIGN

A repeated-measures design was utilised to compare the speech perception of the participants with two configurations of the new adaptive NLFC processing to their performance with the existing NLFC. The outcome measures included the University of Western Ontario Plurals test, the Consonant-Nucleus-Consonant word recognition test, and the Phonak Phoneme Perception test.

STUDY SAMPLE

Study participants included 14 children, aged 6-17 years, with mild-to-severe low-frequency hearing loss and severe-to-profound high-frequency hearing loss.

RESULTS

The results indicated that the use of the new adaptive NLFC processing resulted in significantly better average word recognition and plural detection relative to the conventional NLFC processing.

CONCLUSION

Overall, the adaptive NLFC processing evaluated in this study has the potential to significantly improve speech perception relative to conventional NLFC processing.

Acoustic and perceptual effects of amplitude and frequency compression on high-frequency speech

This study investigated how six different amplification methods influence acoustic properties, and subsequently perception, of high-frequency cues in fricatives that have been processed with conventional full bandwidth amplification or nonlinear frequency compression (NFC)-12 conditions total. Amplification methods included linear gain, fast/slow-acting wide dynamic range compression crossed with fixed/individualized compression parameters, and a method with adaptive time constants. Twenty-one hearing-impaired listeners identified seven fricatives in nonsense syllables produced by female talkers. For NFC stimuli, frequency-compressed filters that precisely aligned 1/3-octave bands between input and output were used to quantify effective compression ratio, audibility, and temporal envelope modulation relative to the input. Results indicated significant relationships between these acoustic properties, each of which contributed significantly to fricative recognition across the entire corpus of stimuli. Recognition was significantly better for NFC stimuli compared with full bandwidth stimuli, regardless of the amplification method, which had complementary effects on audibility and envelope modulation. Furthermore, while there were significant differences in recognition across the amplification methods, they were not consistent across phonemes. Therefore, neither recognition nor acoustic data overwhelmingly suggest that one amplification method should be used over another for transmission of high-frequency cues in isolated syllables. Longer duration stimuli and more realistic listening conditions should be examined.

Quality ratings of frequency-compressed speech by participants with extensive high-frequency dead regions in the cochlea

OBJECTIVE

The objective was to assess the degradation of speech sound quality produced by frequency compression for listeners with extensive high-frequency dead regions (DRs).

DESIGN

Quality ratings were obtained using values of the starting frequency (Sf) of the frequency compression both below and above the estimated edge frequency, fe, of each DR. Thus, the value of Sf often fell below the lowest value currently used in clinical practice. Several compression ratios were used for each value of Sf. Stimuli were sentences processed via a prototype hearing aid based on Phonak Exélia Art P.

STUDY SAMPLE

Five participants (eight ears) with extensive high-frequency DRs were tested.

RESULTS

Reductions of sound-quality produced by frequency compression were small to moderate. Ratings decreased significantly with decreasing Sf and increasing CR. The mean ratings were lowest for the lowest Sf and highest CR. Ratings varied across participants, with one participant rating frequency compression lower than no frequency compression even when Sf was above fe.

CONCLUSIONS

Frequency compression degraded sound quality somewhat for this small group of participants with extensive high-frequency DRs. The degradation was greater for lower values of Sf relative to fe, and for greater values of CR. Results varied across participants.

Evaluation of a Frequency-Lowering Algorithm for Adults With High-Frequency Hearing Loss

The objective was to determine the effects of a frequency-lowering algorithm (frequency composition, Fcomp) on consonant identification, word-final /s, z/ detection, the intelligibility of sentences in noise, and subjective benefit, for people with high-frequency hearing loss, including people with dead regions (DRs) in the cochlea. A single-blind randomized crossover design was used. Performance with Bernafon Acriva 9 hearing aids was compared with Fcomp off and Fcomp on. Participants wore the hearing aids in each condition in a counterbalanced order. Data were collected after at least 8 weeks of experience with a condition. Outcome measures were audibility, scores from the speech perception tests, and scores from a questionnaire comparing self-perceived hearing ability with Fcomp off and Fcomp on. Ten adults with mild to severe high-frequency hearing loss (seven with extensive DRs, one with patchy or restricted DRs, and two with no DR) were tested. Fcomp improved the audibility of high-frequency sounds for 6 out of 10 participants. There was no overall effect of Fcomp on consonant identification, but the pattern of consonant confusions varied across conditions and participants. For word-final /s, z/ detection, performance was significantly better with Fcomp on than with Fcomp off. Questionnaire scores showed no differences between conditions. In summary, Fcomp improved word-final /s, z/ detection. No benefit was found for the other measures.

Nonlinear frequency compression: Influence of start frequency and input bandwidth on consonant and vowel recognition

By varying parameters that control nonlinear frequency compression (NFC), this study examined how different ways of compressing inaudible mid- and/or high-frequency information at lower frequencies influences perception of consonants and vowels. Twenty-eight listeners with mild to moderately severe hearing loss identified consonants and vowels from nonsense syllables in noise following amplification via a hearing aid simulator. Low-pass filtering and the selection of NFC parameters fixed the output bandwidth at a frequency representing a moderately severe (3.3 kHz, group MS) or a mild-to-moderate (5.0 kHz, group MM) high-frequency loss. For each group (n = 14), effects of six combinations of NFC start frequency (SF) and input bandwidth [by varying the compression ratio (CR)] were examined. For both groups, the 1.6 kHz SF significantly reduced vowel and consonant recognition, especially as CR increased; whereas, recognition was generally unaffected if SF increased at the expense of a higher CR. Vowel recognition detriments for group MS were moderately correlated with the size of the second formant frequency shift following NFC. For both groups, significant improvement (33%-50%) with NFC was confined to final /s/ and /z/ and to some VCV tokens, perhaps because of listeners' limited exposure to each setting. No set of parameters simultaneously maximized recognition across all tokens.

Masking Release in Children and Adults With Hearing Loss When Using Amplification

PURPOSE

This study compared masking release for adults and children with normal hearing and hearing loss. For the participants with hearing loss, masking release using simulated hearing aid amplification with 2 different compression speeds (slow, fast) was compared.

METHOD

Sentence recognition in unmodulated noise was compared with recognition in modulated noise (masking release). Recognition was measured for participants with hearing loss using individualized amplification via the hearing-aid simulator.

RESULTS

Adults with hearing loss showed greater masking release than the children with hearing loss. Average masking release was small (1 dB) and did not depend on hearing status. Masking release was comparable for slow and fast compression.

CONCLUSIONS

The use of amplification in this study contrasts with previous studies that did not use amplification. The results suggest that when differences in audibility are reduced, participants with hearing loss may be able to take advantage of dips in the noise levels, similar to participants with normal hearing. Although children required a more favorable signal-to-noise ratio than adults for both unmodulated and modulated noise, masking release was not statistically different. However, the ability to detect a difference may have been limited by the small amount of masking release observed.

Harmonic Frequency Lowering: Effects on the Perception of Music Detail and Sound Quality

A novel algorithm for frequency lowering in music was developed and experimentally tested in hearing-impaired listeners. Harmonic frequency lowering (HFL) combines frequency transposition and frequency compression to preserve the harmonic content of music stimuli. Listeners were asked to make judgments regarding detail and sound quality in music stimuli. Stimuli were presented under different signal processing conditions: original, low-pass filtered, HFL, and nonlinear frequency compressed. Results showed that participants reported perceiving the most detail in the HFL condition. In addition, there was no difference in sound quality across conditions.

Neural-scaled entropy predicts the effects of nonlinear frequency compression on speech perception

The Neural-Scaled Entropy (NSE) model quantifies information in the speech signal that has been altered beyond simple gain adjustments by sensorineural hearing loss (SNHL) and various signal processing. An extension of Cochlear-Scaled Entropy (CSE) [Stilp, Kiefte, Alexander, and Kluender (2010). J. Acoust. Soc. Am. 128(4), 2112-2126], NSE quantifies information as the change in 1-ms neural firing patterns across frequency. To evaluate the model, data from a study that examined nonlinear frequency compression (NFC) in listeners with SNHL were used because NFC can recode the same input information in multiple ways in the output, resulting in different outcomes for different speech classes. Overall, predictions were more accurate for NSE than CSE. The NSE model accurately described the observed degradation in recognition, and lack thereof, for consonants in a vowel-consonant-vowel context that had been processed in different ways by NFC. While NSE accurately predicted recognition of vowel stimuli processed with NFC, it underestimated them relative to a low-pass control condition without NFC. In addition, without modifications, it could not predict the observed improvement in recognition for word final /s/ and /z/. Findings suggest that model modifications that include information from slower modulations might improve predictions across a wider variety of conditions.