Extended High-Frequency Bandwidth Improves Speech Reception in the Presence of Spatially Separated Masking Speech

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.

Extended High-Frequency Thresholds: Associations With Demographic and Risk Factors, Cognitive Ability, and Hearing Outcomes in Middle-Aged and Older Adults

OBJECTIVES

This study had two objectives: to examine associations between extended high-frequency (EHF) thresholds, demographic factors (age, sex, race/ethnicity), risk factors (cardiovascular, smoking, noise exposure, occupation), and cognitive abilities; and to determine variance explained by EHF thresholds for speech perception in noise, self-rated workload/effort, and self-reported hearing difficulties.

DESIGN

This study was a retrospective analysis of a data set from the MUSC Longitudinal Cohort Study of Age-related Hearing Loss. Data from 347 middle-aged adults (45 to 64 years) and 694 older adults (≥ 65 years) were analyzed for this study. Speech perception was quantified using low-context Speech Perception In Noise (SPIN) sentences. Self-rated workload/effort was measured using the effort prompt from the National Aeronautics and Space Administration-Task Load Index. Self-reported hearing difficulty was assessed using the Hearing Handicap Inventory for the Elderly/Adults. The Wisconsin Card Sorting Task and the Stroop Neuropsychological Screening Test were used to assess selected cognitive abilities. Pure-tone averages representing conventional and EHF thresholds between 9 and 12 kHz (PTA(9 - 12 kHz)) were utilized in simple linear regression analyses to examine relationships between thresholds and demographic and risk factors or in linear regression models to assess the contributions of PTA(9 - 12 kHz) to the variance among the three outcomes of interest. Further analyses were performed on a subset of individuals with thresholds ≤ 25 dB HL at all conventional frequencies to control for the influence of hearing loss on the association between PTA(9 - 12 kHz) and outcome measures.

RESULTS

PTA(9 - 12 kHz) was higher in males than females, and was higher in White participants than in racial Minority participants. Linear regression models showed the associations between cardiovascular risk factors and PTA(9 - 12 kHz) were not statistically significant. Older adults who reported a history of noise exposure had higher PTA(9 - 12 kHz) than those without a history, while associations between noise history and PTA(9 - 12 kHz) did not reach statistical significance for middle-aged participants. Linear models adjusting for age, sex, race and noise history showed that higher PTA(9 - 12 kHz) was associated with greater self-perceived hearing difficulty and poorer speech recognition scores in noise for both middle-aged and older participants. Workload/effort was significantly related to PTA(9 - 12 kHz) for middle-aged, but not older, participants, while cognitive task performance was correlated with PTA(9 - 12 kHz) only for older participants. In general, PTA(9 - 12 kHz)did not account for additional variance in outcome measures as compared to conventional pure-tone thresholds, with the exception of self-reported hearing difficulties in older participants. Linear models adjusting for age and accounting for subject-level correlations in the subset analyses revealed no association between PTA(9 - 12 kHz)and outcomes of interest.

CONCLUSIONS

EHF thresholds show age-, sex-, and race-related patterns of elevation that are similar to what is observed for conventional thresholds. The current results support the need for more research to determine the utility of adding EHF thresholds to routine audiometric assessment with middle-aged and older adults.

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.

Midlife Speech Perception Deficits: Impact of Extended High-Frequency Hearing, Peripheral Neural Function, and Cognitive Abilities

OBJECTIVES

The objectives of the present study were to investigate the effects of age-related changes in extended high-frequency (EHF) hearing, peripheral neural function, working memory, and executive function on speech perception deficits in middle-aged individuals with clinically normal hearing.

DESIGN

We administered a comprehensive assessment battery to 37 participants spanning the age range of 20 to 56 years. This battery encompassed various evaluations, including standard and EHF pure-tone audiometry, ranging from 0.25 to 16 kHz. In addition, we conducted auditory brainstem response assessments with varying stimulation rates and levels, a spatial release from masking (SRM) task, and cognitive evaluations that involved the Trail Making test (TMT) for assessing executive function and the Abbreviated Reading Span test (ARST) for measuring working memory.

RESULTS

The results indicated a decline in hearing sensitivities at EHFs and an increase in completion times for the TMT with age. In addition, as age increased, there was a corresponding decrease in the amount of SRM. The declines in SRM were associated with age-related declines in hearing sensitivity at EHFs and TMT performance. While we observed an age-related decline in wave I responses, this decline was primarily driven by age-related reductions in EHF thresholds. In addition, the results obtained using the ARST did not show an age-related decline. Neither the auditory brainstem response results nor ARST scores were correlated with the amount of SRM.

CONCLUSIONS

These findings suggest that speech perception deficits in middle age are primarily linked to declines in EHF hearing and executive function, rather than cochlear synaptopathy or working memory.

Effects of Stimulus Type on 16-kHz Detection Thresholds

OBJECTIVES

Audiometric testing typically does not include frequencies above 8 kHz. However, recent research suggests that extended high-frequency (EHF) sensitivity could affect hearing in natural communication environments. Clinical assessment of hearing often employs pure tones and frequency-modulated (FM) tones interchangeably regardless of frequency. The present study was designed to evaluate how the stimulus chosen to measure EHF thresholds affects estimates of hearing sensitivity.

DESIGN

The first experiment used standard audiometric procedures to measure 8- and 16-kHz thresholds for 5- to 28-year olds with normal hearing in the standard audiometric range (250 to 8000 Hz). Stimuli were steady tones, pulsed tones, and FM tones. The second experiment tested 18- to 28-year olds with normal hearing in the standard audiometric range using psychophysical procedures to evaluate how changes in sensitivity as a function of frequency affect detection of stimuli that differ with respect to bandwidth, including bands of noise. Thresholds were measured using steady tones, pulsed tones, FM tones, narrow bands of noise, and one-third-octave bands of noise at a range of center frequencies in one ear.

RESULTS

In experiment 1, thresholds improved with increasing age at 8 kHz and worsened with increasing age at 16 kHz. Thresholds for individual participants were relatively similar for steady, pulsed, and FM tones at 8 kHz. At 16 kHz, mean thresholds were approximately 5 dB lower for FM tones than for steady or pulsed tones. This stimulus effect did not differ as a function of age. Experiment 2 replicated this greater stimulus effect at 16 kHz than at 8 kHz and showed that the slope of the audibility curve accounted for these effects.

CONCLUSIONS

Contrary to prior expectations, there was no evidence that the choice of stimulus type affected school-age children more than adults. For individual participants, audiometric thresholds at 16 kHz were as much as 20 dB lower for FM tones than for steady tones. Threshold differences across stimuli at 16 kHz were predicted by differences in audibility across frequency, which can vary markedly between listeners. These results highlight the importance of considering spectral width of the stimulus used to evaluate EHF thresholds.

High-Frequency Gain and Maximum Output Effects on Speech Recognition in Bone-Conduction Hearing Devices: Blinded Study

INTRODUCTION

Bone-conduction hearing device (BCHD) uses natural sound transmission through bone and soft tissue, directly to the cochlea, via an external processor that captures and processes sound, which is converted into mechanical vibrations. Key parameters, as maximum power output (MPO) and broader frequency range (FR), must be considered when indicating a BCHD because they can be decisive for speech recognition, especially under listening challenge conditions.

OBJECTIVES

Compare hearing performance and speech recognition in noise of two sound processors (SPs), with different features of MPO and FR, among BCHD users.

MATERIALS AND METHODS

This single-blinded, comparative, observational study evaluated 21 individuals Baha 4 system users with conductive or mixed hearing impairment. The free-field audiometry and speech recognition results were blindly collected under the following conditions: unaided, with Baha 5, and with Baha 6 Max SP.

RESULTS

In free-field audiometry, significant differences were observed between the SP at 0.25, 3, 4, 6, and 8 kHz, with Baha 6 Max outperforming Baha 5. The Baha 6 Max provided significantly better speech recognition than Baha 5 under all the speech in noise conditions evaluated. Separating the transcutaneous from the percutaneous users, Baha 6 Max Attract SP provided the best results and significantly lowered the free-field thresholds than Baha 5 Attract. The Baha 6 Max also significantly improved speech recognition in noise, among both Attract and Connect users.

CONCLUSION

The present study revealed that the greater MPO and broader FR of the Baha 6 Max device helped increase high-frequency gain and improved speech recognition in BCHD-experimented users.

The relationship between extended high-frequency hearing and the binaural spatial advantage in young to middle-aged firefightersa)

Relationships between extended high-frequency (EHF) thresholds and speech-in-spatialized noise were examined in firefighters with a history of occupational noise and airborne toxin exposure. Speech recognition thresholds were measured for co-located and spatially separated (±90° azimuth) sentences in a competing signal using the Listening in Spatialized Noise-Sentences test. EHF hearing was significantly correlated with the spatial advantage, indicating that firefighters with poorer EHF thresholds experienced less benefit from spatial separation. The correlation between EHF thresholds and spatial hearing remained significant after controlling for age. Deficits in EHF and spatial hearing suggest firefighters may experience compromised speech understanding in job-related complex acoustic environments.

Representations of fricatives in subcortical model responses: Comparisons with human consonant perception

Fricatives are obstruent sound contrasts made by airflow constrictions in the vocal tract that produce turbulence across the constriction or at a site downstream from the constriction. Fricatives exhibit significant intra/intersubject and contextual variability. Yet, fricatives are perceived with high accuracy. The current study investigated modeled neural responses to fricatives in the auditory nerve (AN) and inferior colliculus (IC) with the hypothesis that response profiles across populations of neurons provide robust correlates to consonant perception. Stimuli were 270 intervocalic fricatives (10 speakers × 9 fricatives × 3 utterances). Computational model response profiles had characteristic frequencies that were log-spaced from 125 Hz to 8 or 20 kHz to explore the impact of high-frequency responses. Confusion matrices generated by k-nearest-neighbor subspace classifiers were based on the profiles of average rates across characteristic frequencies as feature vectors. Model confusion matrices were compared with published behavioral data. The modeled AN and IC neural responses provided better predictions of behavioral accuracy than the stimulus spectra, and IC showed better accuracy than AN. Behavioral fricative accuracy was explained by modeled neural response profiles, whereas confusions were only partially explained. Extended frequencies improved accuracy based on the model IC, corroborating the importance of extended high frequencies in speech perception.

Speech understanding and extended high-frequency hearing sensitivity in blast-exposed veteransa)

Auditory difficulties reported by normal-hearing Veterans with a history of blast exposure are primarily thought to stem from processing deficits in the central nervous system. However, previous work on speech understanding in noise difficulties in this patient population have only considered peripheral hearing thresholds in the standard audiometric range. Recent research suggests that variability in extended high-frequency (EHF; >8 kHz) hearing sensitivity may contribute to speech understanding deficits in normal-hearing individuals. Therefore, this work was designed to identify the effects of blast exposure on several common clinical speech understanding measures and EHF hearing sensitivity. This work also aimed to determine whether variability in EHF hearing sensitivity contributes to speech understanding difficulties in normal-hearing blast-exposed Veterans. Data from 41 normal- or near-normal-hearing Veterans with a history of blast exposure and 31 normal- or near-normal-hearing control participants with no history of head injury were employed in this study. Analysis identified an effect of blast exposure on several speech understanding measures but showed no statistically significant differences in EHF thresholds between participant groups. Data showed that variability in EHF hearing sensitivity did not contribute to group-related differences in speech understanding, although study limitations impact interpretation of these results.

Differential benefits of unmasking extended high-frequency content of target or background speech

Current evidence supports the contribution of extended high frequencies (EHFs; >8 kHz) to speech recognition, especially for speech-in-speech scenarios. However, it is unclear whether the benefit of EHFs is due to phonetic information in the EHF band, EHF cues to access phonetic information at lower frequencies, talker segregation cues, or some other mechanism. This study investigated the mechanisms of benefit derived from a mismatch in EHF content between target and masker talkers for speech-in-speech recognition. EHF mismatches were generated using full band (FB) speech and speech low-pass filtered at 8 kHz. Four filtering combinations with independently filtered target and masker speech were used to create two EHF-matched and two EHF-mismatched conditions for one- and two-talker maskers. Performance was best with the FB target and the low-pass masker in both one- and two-talker masker conditions, but the effect was larger for the two-talker masker. No benefit of an EHF mismatch was observed for the low-pass filtered target. A word-by-word analysis indicated higher recognition odds with increasing EHF energy level in the target word. These findings suggest that the audibility of target EHFs provides target phonetic information or target segregation and selective attention cues, but that the audibility of masker EHFs does not confer any segregation benefit.

Predicting Behavioral Threshold at 6 and 8 kHz for Children and Adults Based on the Auditory Brainstem Response

PURPOSE

Common clinical application of auditory brainstem response (ABR) testing is limited to 0.25-4 kHz. Prior research has demonstrated associations between ABR and behavioral thresholds for tone burst stimuli > 4 kHz in adults, but there are no comparable data for children. The ability to predict behavioral thresholds > 4 kHz clinically based on the ABR would provide valuable audiologic information for individuals who are unable to provide behavioral thresholds. This study included children with hearing loss and children with normal hearing to determine the association between ABR and behavioral thresholds at 6 and 8 kHz.

METHOD

ABR and behavioral thresholds were obtained for children ages 4.7-16.7 years (M = 10.5, SD = 3.4) with sensorineural hearing loss (n = 24) or normal hearing sensitivity (n = 16) and for adults ages 18.4-54.4 years (M = 32.7, SD = 10.4) with sensorineural hearing loss (n = 13) or normal hearing sensitivity (n = 11). Thresholds obtained for 6 and 8 kHz using ABR and conventional audiometry were compared.

RESULTS

Differences between ABR and behavioral thresholds averaged 5-6 dB for both children and adults for both test frequencies, with differences of ≤ 20 dB in all instances. Linear mixed modeling for data from participants with hearing loss suggested that ABR threshold is a good predictor of behavioral threshold at 6 and 8 kHz for both children and adults. Test specificity was 100%; no participants with behavioral thresholds ≤ 20 dB HL had ABR thresholds > 25 dB nHL.

CONCLUSIONS

Initial evidence suggests that ABR testing at 6 and 8 kHz is reliable for estimating behavioral threshold in listeners with hearing loss and accurately identifies normal hearing sensitivity. The results of this study contribute to efforts to improve outcomes for vulnerable populations by reducing barriers to clinical implementation of ABR testing at > 4 kHz.

Extending the High-Frequency Bandwidth and Predicting Speech-in-Noise Recognition: Building on the Work of Pat Stelmachowicz

Recent work has demonstrated that high-frequency (>6 kHz) and extended high-frequency (EHF; >8 kHz) hearing is valuable for speech-in-noise recognition. Several studies also indicate that EHF pure-tone thresholds predict speech-in-noise performance. These findings contradict the broadly accepted "speech bandwidth" that has historically been limited to below 8 kHz. This growing body of work is a tribute to the work of Pat Stelmachowicz, whose research was instrumental in revealing the limitations of the prior speech bandwidth work, particularly for female talkers and child listeners. Here, we provide a historical review that demonstrates how the work of Stelmachowicz and her colleagues paved the way for subsequent research to measure effects of extended bandwidths and EHF hearing. We also present a reanalysis of previous data collected in our lab, the results of which suggest that 16-kHz pure-tone thresholds are consistent predictors of speech-in-noise performance, regardless of whether EHF cues are present in the speech signal. Based on the work of Stelmachowicz, her colleagues, and those who have come afterward, we argue that it is time to retire the notion of a limited speech bandwidth for speech perception for both children and adults.

Auditory Brainstem Responses at 6 and 8 kHz in Infants With Normal Hearing

PURPOSE

Normative auditory brainstem response (ABR) data for infants and young children are available for 0.25-4 kHz, limiting clinical assessment to this range. As such, the high-frequency hearing sensitivity of infants and young children remains unknown until behavioral testing can be completed, often not until late preschool or early school ages. The purpose of this study was to obtain normative ABR data at 6 and 8 kHz in young infants.

METHOD

Participants were 173 full-term infants seen clinically for ABR testing at 0.4-6.7 months chronological age (M = 1.4 months, SD = 1.0), 97% of whom were ≤ 12 weeks chronological age. Stimuli included 6 and 8 kHz tone bursts presented at a rate of 27.7/s or 30.7/s using Blackman window gating with six cycles (6 kHz) or eight cycles (8 kHz) rise/fall time and no plateau. Presentation levels included 20, 40, and 60 dB nHL. The ABR threshold was estimated in 5- to 10-dB steps.

RESULTS

As previously observed with lower frequency stimuli, ABR waveforms obtained in response to 6 and 8 kHz tone bursts decreased in latency with increasing intensity and increasing age. Latency was shorter for 8-kHz tone bursts than 6-kHz tone bursts. Data tables are presented for clinical reference for infants ≤ 4 weeks, 4.1-8 weeks, and 8.1-12 weeks chronological age including median ABR latency for Waves I, III, and V and the upper and lower boundaries of the 90% prediction interval. Interpeak Latencies I-III, III-V, and I-V are also reported.

CONCLUSION

The results from this study demonstrate that ABR assessment at 6 and 8 kHz is feasible for young infants within a standard clinical appointment and provide reference data for clinical interpretation of ABR waveforms for frequencies above 4 kHz.

On the use of the TIMIT, QuickSIN, NU-6, and other widely used bandlimited speech materials for speech perception experiments

The use of spectrally degraded speech signals deprives listeners of acoustic information that is useful for speech perception. Several popular speech corpora, recorded decades ago, have spectral degradations, including limited extended high-frequency (EHF) (>8 kHz) content. Although frequency content above 8 kHz is often assumed to play little or no role in speech perception, recent research suggests that EHF content in speech can have a significant beneficial impact on speech perception under a wide range of natural listening conditions. This paper provides an analysis of the spectral content of popular speech corpora used for speech perception research to highlight the potential shortcomings of using bandlimited speech materials. Two corpora analyzed here, the TIMIT and NU-6, have substantial low-frequency spectral degradation (<500 Hz) in addition to EHF degradation. We provide an overview of the phenomena potentially missed by using bandlimited speech signals, and the factors to consider when selecting stimuli that are sensitive to these effects.

Examining the Profile of Noise-Induced Cochlear Synaptopathy Using iPhone Health App Data and Cochlear and Brainstem Electrophysiological Responses to Fast Clicks Rates

Little is known about objective classifying of noise exposure risk levels in personal listening device (PLD) users and electrophysiologic evidence of cochlear synaptopathy at very fast click rates. The aim of the study was to objectively classify noise exposure risk using iPhone Health app and identify signs of cochlear synaptopathy using behavioral and electrophysiologic measures. Thirty normal-hearing females (aged 18-26 years) were grouped based on their iPhone Health app's 6-month listening level and noise exposure data into low-risk and high-risk groups. They were assessed using a questionnaire, extended high-frequency (EHF) audiometry, QuickSIN test, distortion-product otoacoustic emission (DPOAE), and simultaneous recording of electrocochleography (ECochG) and auditory brainstem response (ABR) at three click rates (19.5/s, 97.7/s, 234.4/s). A series of ANOVAs and independent samples t -test were conducted for group comparison. Both groups had within-normal EHF hearing thresholds and DPOAEs. However, the high-risk participants were over twice as likely to suffer from tinnitus, had abnormally large summating potential to action potential amplitude and area ratios at fast rates, and had slightly smaller waves I and V amplitudes. The high-risk group demonstrated a profile of behavioral and objective signs of cochlear synaptopathy based on ECochG and ABR recordings at fast click rates. The findings in this study suggest that the iPhone Health app may be a useful tool for further investigation into cochlear synaptopathy in PLD users.

Extended high-frequency audiometry in research and clinical practice

Audiometric testing in research and in clinical settings rarely considers frequencies above 8 kHz. However, the sensitivity of young healthy ears extends to 20 kHz, and there is increasing evidence that testing in the extended high-frequency (EHF) region, above 8 kHz, might provide valuable additional information. Basal (EHF) cochlear regions are especially sensitive to the effects of aging, disease, ototoxic drugs, and possibly noise exposure. Hence, EHF loss may be an early warning of damage, useful for diagnosis and for monitoring hearing health. In certain environments, speech perception may rely on EHF information, and there is evidence for an association between EHF loss and speech perception difficulties, although this may not be causal: EHF loss may instead be a marker for sub-clinical damage at lower frequencies. If there is a causal relation, then amplification in the EHF range may be beneficial if the technical difficulties can be overcome. EHF audiometry in the clinic presents with no particular difficulty, the biggest obstacle being lack of specialist equipment. Currently, EHF audiometry has limited but increasing clinical application. With the development of international guidelines and standards, it is likely that EHF testing will become widespread in future.

Effect of Masker Head Orientation, Listener Age, and Extended High-Frequency Sensitivity on Speech Recognition in Spatially Separated Speech

OBJECTIVES

Masked speech recognition is typically assessed as though the target and background talkers are all directly facing the listener. However, background speech in natural environments is often produced by talkers facing other directions, and talker head orientation affects the spectral content of speech, particularly at the extended high frequencies (EHFs; >8 kHz). This study investigated the effect of masker head orientation and listeners' EHF sensitivity on speech-in-speech recognition and spatial release from masking in children and adults.

DESIGN

Participants were 5- to 7-year-olds (n = 15) and adults (n = 34), all with normal hearing up to 8 kHz and a range of EHF hearing thresholds. Speech reception thresholds (SRTs) were measured for target sentences recorded from a microphone directly in front of the talker's mouth and presented from a loudspeaker directly in front of the listener, simulating a target directly in front of and facing the listener. The maskers were two streams of concatenated words recorded from a microphone located at either 0° or 60° azimuth, simulating masker talkers facing the listener or facing away from the listener, respectively. Maskers were presented in one of three spatial conditions: co-located with the target, symmetrically separated on either side of the target (+54° and -54° on the horizontal plane), or asymmetrically separated to the right of the target (both +54° on the horizontal plane).

RESULTS

Performance was poorer for the facing than for the nonfacing masker head orientation. This benefit of the nonfacing masker head orientation, or head orientation release from masking (HORM), was largest under the co-located condition, but it was also observed for the symmetric and asymmetric masker spatial separation conditions. SRTs were positively correlated with the mean 16-kHz threshold across ears in adults for the nonfacing conditions but not for the facing masker conditions. In adults with normal EHF thresholds, the HORM was comparable in magnitude to the benefit of a symmetric spatial separation of the target and maskers. Although children benefited from the nonfacing masker head orientation, their HORM was reduced compared to adults with normal EHF thresholds. Spatial release from masking was comparable across age groups for symmetric masker placement, but it was larger in adults than children for the asymmetric masker.

CONCLUSIONS

Masker head orientation affects speech-in-speech recognition in children and adults, particularly those with normal EHF thresholds. This is important because masker talkers do not all face the listener under most natural listening conditions, and assuming a midline orientation would tend to overestimate the effect of spatial separation. The benefits associated with EHF audibility for speech-in-speech recognition may warrant clinical evaluation of thresholds above 8 kHz.

The Importance of Extended High-Frequency Speech Information in the Recognition of Digits, Words, and Sentences in Quiet and Noise

OBJECTIVES

In pure-tone audiometry, hearing thresholds are typically measured up to 8 kHz. Recent research has shown that extended high-frequency (EHF; frequencies >8 kHz) speech information improves speech recognition. However, it is unclear whether the EHF benefit is present for different types of speech material. This study assesses the added value of EHF information for speech recognition in noise for digit triplets, consonant-vowel-consonant (CVC) words, and sentences; and for speech recognition in quiet for CVC.

DESIGN

Twenty-four young adults with normal-hearing thresholds up to 16 kHz performed a listening experiment in quiet and in noise in a within-subject repeated measures design. Stimuli were presented monaurally. Steady state speech-shaped noise at a fixed signal to noise ratio was used for measurements in noise. Listening conditions varied only in terms of available EHF information. Stimuli were presented in three different conditions: (1) both speech and noise broadband, (2) speech broadband and noise low-pass filtered at 8 kHz, and (3) both speech and noise low-pass filtered at 8 kHz. In the speech-in-quiet experiment, stimuli (CVC) were high-pass filtered at 3 kHz and presented in two conditions: (1) with EHF information and (2) without EHF information.

RESULTS

In the speech-in-noise experiment, for all speech material, the highest scores were achieved in the condition where the noise was low-pass filtered at 8 kHz and speech unfiltered; the lowest scores were obtained in the condition where both speech and noise were low-pass filtered at 8 kHz. Adding speech frequencies above 8 kHz improved the median recognition scores by 75.0%, 21.8%, and 23.8% for digit triplets, words, and sentences, respectively, at a fixed signal to noise ratio. In the speech-in-quiet experiment, median recognition scores were 7.8% higher in the condition where the EHF information was available, as opposed to when it was not.

CONCLUSIONS

Speech information for frequencies above 8 kHz contributes to speech recognition in noise. It also contributes to speech recognition in quiet when information below 3 kHz is absent. Our results suggest that EHFs may be relevant in challenging listening conditions and should be measured in pure-tone audiometry to get a complete picture of a person's hearing. Further, results of speech recognition tests may vary when different recording and/or measurement equipment is used with different frequency responses above 8 kHz.

Identifying Subclinical Hearing Loss: Extended Audiometry and Word Recognition in Noise

INTRODUCTION

Normal-hearing people often have complaints about the ability to recognize speech in noise. Such disabilities are not typically assessed with conventional audiometry. Suprathreshold temporal deficits might contribute to reduced word recognition in noise as well as reduced temporally based binaural release of masking for speech. Extended high-frequency audibility (>8 kHz) has also been shown to contribute to speech perception in noise. The primary aim of this study was to compare conventional audiometric measures with measures that could reveal subclinical deficits.

METHODS

Conventional and extended high-frequency audiometry was done with 119 normal-hearing people ranging in age from 18 to 72. The ability to recognize words in noise was evaluated with and without differences in temporally based spatial cues. A low-uncertainty, closed-set word recognition task was used to limit cognitive influences.

RESULTS

In normal-hearing listeners, word recognition in noise ability decreases significantly with increasing pure-tone average (PTA). On average, signal-to-noise ratios worsened by 5.7 and 6.0 dB over the normal range, for the diotic and dichotic conditions, respectively. When controlling for age, a significant relationship remained in the diotic condition. Measurement error was estimated at 1.4 and 1.6 dB for the diotic and dichotic conditions, respectively. Controlling for both PTA and age, EHF-PTAs showed significant partial correlations with SNR50 in both conditions (ρ = 0.30 and 0.23). Temporally based binaural release of masking worsened with age by 1.94 dB from 18 to 72 years old but showed no significant relationship with either PTA.

CONCLUSIONS

All three assessments in this study demonstrated hearing problems independently of those observed in conventional audiometry. Considerable degradations in word recognition in noise abilities were observed as PTAs increased within the normal range. The use of an efficient words-in-noise measure might help identify functional hearing problems for individuals that are traditionally normal hearing. Extended audiometry provided additional predictive power for word recognition in noise independent of both the PTA and age. Temporally based binaural release of masking for word recognition decreased with age independent of PTAs within the normal range, indicating multiple mechanisms of age-related decline with potential clinical impact.

Effects of extended high frequency bandwidth in osseointegrated bone conduction device users

High-frequency hearing above 5000 Hz improves the detection and discrimination of high frequency phonemes. Improved access to high-frequency hearing may be particularly advantageous in unilaterally deafened listeners who experience reduced access to high frequency speech cues on their impaired side and decreased speech perception abilities in competing noise. This study aimed to investigate the effects of extended high-frequency bandwidth on speech perception in unilaterally deafened osseointegrated bone conduction hearing device recipients. To study the effect of extended high-frequency bandwidth, participants underwent aided testing in narrow bandwidth and extended high-frquency bandwidth BCD listening conditions. Aided word and phoneme recognition in quiet was assessed at soft and conversational speech levels with the better ear plugged. Aided thresholds and Ling 6 phoneme sounds were also assessed in quiet with the better ear plugged. Speech perception in noise was assessed at ± 90° and co-located at 0° using the adaptive Hearing in Noise Test. Findings demonstrate a significant improvement in speech perception outcomes when listening with extended high-frequency bandwidth. Extended high-frequency bandwidth significantly improved word and phoneme recognition for soft and average conversational speech. The largest effects were observed for voiceless phonemes. Results suggest use of bone conduction devices with extended high-frequency bandwidth result in improved hearing outcomes when compared with narrow bandwidth bone conduction devices.

Extended High-frequency Hearing Impairment Despite a Normal Audiogram: Relation to Early Aging, Speech-in-noise Perception, Cochlear Function, and Routine Earphone Use

OBJECTIVES

Humans can hear up to 20 kHz. Emerging evidence suggests that hearing in the extended high frequencies (EHFs; >8 kHz) contributes to speech perception in noise. The objective of the present study was to describe the features of EHF hearing impairment in young adults with normal standard audiograms (0.25-8 kHz). Specifically, the study goals were to: (1) characterize the EHF hearing impairment and identify potential risk factors; (2) elucidate the age-related changes in EHF hearing; (3) determine the effect of EHF hearing impairment on speech-in-noise recognition; and (4) examine the extent to which EHF hearing impairment influences cochlear functioning in the standard frequencies.

DESIGN

Hearing thresholds at standard frequencies and EHFs (10, 12.5, 14, and 16 kHz), and speech recognition thresholds (SRTs) using digit triplets in multi-talker babble were measured in both ears from 222 participants (19-38 years; n = 444 ears) with normal audiograms (≤20 dB HL at standard frequencies). Test-retest measurement of hearing thresholds was obtained in a subset of 50 participants (100 ears), and clinical distortion product otoacoustic emissions (f2 frequency = 2, 3, 4, and 5 kHz) were recorded in 49 participants (98 ears).

RESULTS

Forty-two of 222 participants had EHF hearing impairment (>20 dB HL for at least one EHF in either ear). Only seven individuals with EHF impairment had significant case history and/or listening-in-noise complaints. A breakpoint in the threshold-age function was observed for the EHFs for males but not for females. Linear mixed models revealed a significant effect of age, pure-tone averages for speech frequencies (0.5, 1, 2, and 4 kHz), and EHFs and group (NH versus EHF hearing impairment) independent of each other on the SRTs. Individuals with EHF hearing impairment had less measurable emissions and when present, had a lower magnitude of otoacoustic emissions relative to NH controls. There was no difference in hearing thresholds, SRTs, or otoacoustic emissions between earphone users and nonusers.

CONCLUSIONS

The hearing thresholds for the EHFs exhibit signs of early auditory aging. Age-related deterioration in auditory function can be observed in the third decade of human life. A breakpoint in the threshold-age function suggests that rapid aging processes are operational at a relatively younger age (21 years) for males. The audibility of EHFs contributes to speech-in-noise recognition. EHF hearing impairment independent of age and speech frequencies can affect speech-in-noise recognition. Reduced distortion product otoacoustic emissions in the standard frequencies may suggest preclinical cochlear degeneration in individuals with EHF hearing impairment.

Investigating Real-World Benefits of High-Frequency Gain in Bone-Anchored Users with Ecological Momentary Assessment and Real-Time Data Logging

Purpose: To compare listening ability (speech reception thresholds) and real-life listening experience in users with a percutaneous bone conduction device (BCD) with two listening programs differing only in high-frequency gain. In situ real-life experiences were recorded with ecological momentary assessment (EMA) techniques combined with real-time acoustical data logging and standard retrospective questionnaires. Methods: Nineteen experienced BCD users participated in this study. They all used a Ponto 4 BCD from Oticon Medical during a 4-week trial period. Environmental data and device parameters (i.e., device usage and volume control) were logged in real-time on an iPhone via a custom iOS research app. At the end of the trial period, subjects filled in APHAB, SSQ, and preference questionnaires. Listening abilities with the two programs were evaluated with speech reception threshold tests. Results: The APHAB and SSQ questionnaires did not reveal any differences between the two listening programs. The EMAs revealed group-level effects, indicating that in speech and noisy listening environments, subjects preferred the default listening program, and found the program with additional high-frequency gain too loud. This finding was corroborated by the volume log—subjects avoided the higher volume control setting and reacted more to changes in environmental sound pressure levels when using the high-frequency gain program. Finally, day-to-day changes in EMAs revealed acclimatization effects in the listening experience for ratings of “sound quality” and “program suitability” of the BCD, but not for ratings of “loudness perception” and “speech understanding”. The acclimatization effect did not differ among the listening programs. Conclusion: Adding custom high-frequency amplification to the BCD target-gain prescription improves speech reception in laboratory tests under quiet conditions, but results in poorer real-life listening experiences due to loudness.

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.

Increased maximum power output may improve speech recognition with bone conduction hearing devices

OBJECTIVE

To investigate the influence of maximum power output of bone conduction hearing devices on speech recognition in quiet and in noise in experienced users of bone conduction hearing devices.

DESIGN

Prospective, randomised cross-over investigation comparing speech recognition performance, subjective sound quality, and device preference between two bone conduction hearing devices with different maximum power outputs.

STUDY SAMPLE

Sixteen adult subjects with conductive or mixed hearing loss.

RESULTS

Both speech recognition in quiet and speech recognition in noise improved significantly when using the device with high vs. lower maximum power output. Mean improvement in word recognition score in quiet was 10.5% and the mean speech reception threshold in noise improved by 0.9 dB SNR. Compared to the device with lower maximum power output, the sound quality was rated significantly higher with the device with high maximum power output, which was also the device of preference for 81% of the subjects.

CONCLUSION

Bone conduction hearing devices with higher maximum power output have the potential to improve speech recognition in both quiet and noisy listening environments.

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.

The Neural Bases of Tinnitus: Lessons from Deafness and Cochlear Implants

Subjective tinnitus is the conscious perception of sound in the absence of any acoustic source. The literature suggests various tinnitus mechanisms, most of which invoke changes in spontaneous firing rates of central auditory neurons resulting from modification of neural gain. Here, we present an alternative model based on evidence that tinnitus is: (1) rare in people who are congenitally deaf, (2) common in people with acquired deafness, and (3) potentially suppressed by active cochlear implants used for hearing restoration. We propose that tinnitus can only develop after fast auditory fiber activity has stimulated the synapse formation between fast-spiking parvalbumin positive (PV⁺) interneurons and projecting neurons in the ascending auditory path and coactivated frontostriatal networks after hearing onset. Thereafter, fast auditory fiber activity promotes feedforward and feedback inhibition mediated by PV⁺ interneuron activity in auditory-specific circuits. This inhibitory network enables enhanced stimulus resolution, attention-driven contrast improvement, and augmentation of auditory responses in central auditory pathways (neural gain) after damage of slow auditory fibers. When fast auditory fiber activity is lost, tonic PV⁺ interneuron activity is diminished, resulting in the prolonged response latencies, sudden hyperexcitability, enhanced cortical synchrony, elevated spontaneous γ oscillations, and impaired attention/stress-control that have been described in previous tinnitus models. Moreover, because fast processing is gained through sensory experience, tinnitus would not exist in congenital deafness. Electrical cochlear stimulation may have the potential to reestablish tonic inhibitory networks and thus suppress tinnitus. The proposed framework unites many ideas of tinnitus pathophysiology and may catalyze cooperative efforts to develop tinnitus therapies.

Auditory Development of Frequency Discrimination at Extended High Frequencies

OBJECTIVES

Hearing in the extended high frequencies (EHFs; >8 kHz) is perceptually and clinically relevant. Recent work suggests the possible role of EHF audibility in natural listening environments (e.g., spatial hearing) and hidden hearing loss. In this article, we examine the development of frequency discrimination (FD) in the EHFs. Specifically, the objectives of the present study were to answer if the developmental timeline for FD is different for EHFs; and whether the discontinuity of FD thresholds across frequency-representing the hypothetical shift from a temporal to place code-for children occurs at about the same frequency as adults.

DESIGN

Thirty-one normal-hearing children (5 to 12 years) and 15 young adults participated in this study. FD thresholds were measured for standard frequencies (1, 2, 4, 6, and 8 kHz) and EHFs (10 and 12.5 kHz) using a three-alternative (odd-ball) forced-choice paradigm. Statistical analysis focused on examining the change of FD thresholds as a function of age and estimating the breakpoints in the discrimination threshold-frequency functions.

RESULTS

FD performance in younger children for EHFs was nearly six times poorer relative to older children and adults; however, there was no effect of test frequency on the child-adult difference. Change-point detection on group data revealed a higher knot frequency-representing the putative transition from temporal to place mechanisms-for adults (9.8 kHz) than children (~6 kHz). Individual spline functions suggest that the knot frequency varied from 2 to 10 kHz across participants.

CONCLUSIONS

The present study provides evidence for a similar rate of maturation of FD for EHFs and standard frequencies. FD at EHFs matures by 10 to 12 years of age. Adult listeners may not all use temporal cues up to 10 kHz. Young children are relatively inefficient in using temporal fine-structure cues for FD at frequencies above 6 kHz.

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.

Extended high frequency hearing and speech perception implications in adults and children

Extended high frequencies (EHF), above 8 kHz, represent a region of the human hearing spectrum that is generally ignored by clinicians and researchers alike. This article is a compilation of contributions that, together, make the case for an essential role of EHF in both normal hearing and auditory dysfunction. We start with the fundamentals of biological and acoustic determinism - humans have EHF hearing for a purpose, for example, the detection of prey, predators, and mates. EHF hearing may also provide a boost to speech perception in challenging conditions and its loss, conversely, might help explain difficulty with the same task. However, it could be that EHF are a marker for damage in the conventional frequency region that is more related to speech perception difficulties. Measurement of EHF hearing in concert with otoacoustic emissions could provide an early warning of age-related hearing loss. In early life, when EHF hearing sensitivity is optimal, we can use it for enhanced phonetic identification during language learning, but we are also susceptible to diseases that can prematurely damage it. EHF audiometry techniques and standardization are reviewed, providing evidence that they are reliable to measure and provide important information for early detection, monitoring and possible prevention of hearing loss in populations at-risk. To better understand the full contribution of EHF to human hearing, clinicians and researchers can contribute by including its measurement, along with measures of speech in noise and self-report of hearing difficulties and tinnitus in clinical evaluations and studies.

Hearing and speech processing in midlife

Middle-aged adults often report a decline in their ability to understand speech in adverse listening situations. However, there has been relatively little research devoted to identifying how early aging affects speech processing, as the majority of investigations into senescent changes in speech understanding compare performance in groups of young and older adults. This paper provides an overview of research on hearing and speech perception in middle-aged adults. Topics covered include both objective and subjective (self-perceived) hearing and speech understanding, listening effort, and audiovisual speech perception. This review ends with justification for future research needed to define the nature, consequences, and remediation of hearing problems in middle-aged adults.

Over-under cartilage tympanoplasty: technique, results and a call for improved reporting

OBJECTIVE

This study aimed to describe the microscopic over-under cartilage tympanoplasty technique, provide hearing results and detail clinically significant complications.

METHOD

This was a retrospective case series chart review study of over-under cartilage tympanoplasty procedures performed by the senior author between January 2015 and January 2019 at three tertiary care centres. Cases were excluded for previous or intra-operative cholesteatoma, if a mastoidectomy was performed during the procedure or if ossiculoplasty was performed. Hearing results and complications were obtained.

RESULTS

Sixty-eight tympanoplasty procedures met the inclusion criteria. The median age was 13 years (range, 3-71 years). The mean improvement in pure tone average was 6 dB (95 per cent confidence interval 4-9 dB; p < 0.0001). The overall perforation closure rate was 97 per cent (n = 66). Revision surgery was recommended for a total of 6 cases (9 per cent) including 2 post-operative perforations, 1 case of middle-ear cholesteatoma and 3 cases of external auditory canal scarring.

CONCLUSION

Over-under cartilage tympanoplasty is effective at improving clinically meaningful hearing with a low rate of post-operative complications.

Peripheral Auditory Involvement in Childhood Listening Difficulty

OBJECTIVES

This study tested the hypothesis that undetected peripheral hearing impairment occurs in children with idiopathic listening difficulties (LiDs), as reported by caregivers using the Evaluation of Children"s Listening and Processing Skills (ECLiPS) validated questionnaire, compared with children with typically developed (TD) listening abilities.

DESIGN

Children with LiD aged 6-14 years old (n = 60, mean age = 9.9 yr) and 54 typical age matched children were recruited from audiology clinical records and from IRB-approved advertisements at hospital locations and in the local and regional areas. Both groups completed standard and extended high-frequency (EHF) pure-tone audiometry, wideband absorbance tympanometry and middle ear muscle reflexes, distortion product and chirp transient evoked otoacoustic emissions. Univariate and multivariate mixed models and multiple regression analysis were used to examine group differences and continuous performance, as well as the influence of demographic factors and pressure equalization (PE) tube history.

RESULTS

There were no significant group differences between the LiD and TD groups for any of the auditory measures tested. However, analyses across all children showed that EHF hearing thresholds, wideband tympanometry, contralateral middle ear muscle reflexes, distortion product, and transient-evoked otoacoustic emissions were related to a history of PE tube surgery. The physiologic measures were also associated with EHF hearing loss, secondary to PE tube history.

CONCLUSIONS

Overall, the results of this study in a sample of children with validated LiD compared with a TD group matched for age and sex showed no significant differences in peripheral function using highly sensitive auditory measures. Histories of PE tube surgery were significantly related to EHF hearing and to a range of physiologic measures in the combined sample.

Comparing Light-Driven Contact Hearing Aids with Acoustic Hearing Aids: Data and Clinical Tips

INTRODUCTION

Contact hearing aids (CHA) offer potential advantages over conventional acoustic hearing aids (AHA) in terms of sound quality, reduced occlusion, and increased high-frequency gain. This study evaluates objective and subjective outcome data for CHA compared to AHA.

METHODS

Clinical outcome data were retrospectively reviewed for patients wearing CHA. Individual and group data were analyzed and then compared to unaided and AHA data. Adverse effects, device complaints, and clinical utility were documented throughout the device fitting and follow-up process.

RESULTS

CHA outcomes were better than unaided hearing and AHA for all patients completing the 3-month CHA trial period (45%). However, CHA return rate was high (55%), most often due to device repair and fit issues. Two patients returned the devices due to poor hearing benefit, though both were off-label audiometric candidates. Significantly more clinical time was required from both audiologists and otolaryngologists to successfully fit and maintain maximum device benefit.

CONCLUSIONS

For proper audiometric and otologic candidates, this light-driven CHA can offer significant improvements in high-frequency sound fidelity, word recognition, and sound quality compared to AHA technology. Administering questionnaires was helpful in illuminating real-world improvements. Device fit, alignment, and quality control issues are improving, though still contributing to high device return rates at this time. Operational factors should be considered when incorporating CHA into a hearing health care practice.

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.

New Medical Device and Therapeutic Approvals in Otolaryngology: State of the Art Review of 2019

OBJECTIVE

To review new devices and drugs relevant to otolaryngology-head and neck surgery that were approved by the US Food and Drug Administration (FDA) in 2019.

DATA SOURCES

Approval notifications for 2019 were extracted from the ENT (ear, nose, and throat) and general and plastic surgery sections of the FDA's medical devices and therapeutics listings.

REVIEW METHODS

New therapeutics and medical devices identified from the query were analyzed by members of the American Academy of Otolaryngology-Head and Neck Surgery's Medical Devices and Drugs Committee. Technologies were assessed by 2 independent reviewers to ascertain relevance to otolaryngology, prioritized, and classified to subspecialty field with critical review based on extant scientific literature.

CONCLUSIONS

Query of the FDA drug and device database returned 105 ENT devices (50 cleared, 55 with premarket approval, and 0 de novo), 543 general and plastic surgery devices (372 cleared, 170 with premarket approval, and 1 de novo), and 46 new otolaryngology-relevant drug approvals that occurred in 2019. Advances spanned all subspecialty areas with otology predominating, primarily due to hearing-related technologies. While scientific evidence was available for all new devices, there was significant heterogeneity in rigor of supporting scientific data.

IMPLICATIONS FOR PRACTICE

Technological and pharmaceutical innovation is an important catalyst for advances in the surgical specialties. Familiarity with new devices and therapeutics in otolaryngology-head and neck surgery ensures that clinicians keep abreast of developments with potential to improve prevailing standards of care.

[High frequency hearing among rural workers exposed to pesticides]

Pesticides may cause a number of health problems and are considered oto-agressive agents. The objective of this study was to investigate the high frequency hearing characteristics of workers both with and without exposure to pesticides, that presented normal conventional audiometry. It involved a cross-sectional study with 87 workers, of both genders, between 19 and 59 years, with formal or informal jobs and some of whom worked with family agriculture, either using pesticides or not, who had taken High-Frequency Audiometry tests. The use of glyphosate was reported by 73% of workers and several pesticide mixtures occurred in 78% of them. There were no cases of proper use of personal protective equipment recommended for the activity. The workers exposed to pesticides had worse results in High-Frequency Audiometry tests in comparison with those who had no contact with pesticides (p < 0.0001). High-Frequency Audiometry has proved to be a useful and effective tool in the early detection of hearing loss caused by pesticides.

Direct-to-Consumer Hearing Devices: Capabilities, Costs, and Cosmetics

Direct-to-consumer (DTC) hearing devices can be purchased without consulting a hearing health professional. This project aims to compare 28 DTC devices with the most popular hearing aid supplied by the U.K. National Health Service (NHS). The comparison was based on technical performance, cosmetic acceptability, and the ability to match commonly used gain and slope targets. Electroacoustic performance was evaluated in a 2-cc coupler. Match to prescription target for both gain and slope was measured on a Knowles Electronic Manikin for Acoustic Research using a mild and also a moderate sloping hearing loss. Using an online blinded paired comparison of each DTC and the NHS reference device, 126 participants (50 were hearing aid users and 76 were nonhearing aid users) assessed the cosmetic appearance and rated their willingness-to-wear the DTC devices. The results revealed that higher purchase prices were generally associated with a better match to prescribed gain–frequency response shapes, lower distortion, wider bandwidth, better cosmetic acceptability, and higher willingness-to-wear. On every parameter measured, there were devices that performed worse than the NHS device. Most of the devices were rated lower in terms of aesthetic design than the NHS device and provided gain–frequency responses and maximum output levels that were markedly different from those prescribed for commonly encountered audiograms. Because of the absence or inflexibility of most of the devices, they have the potential to deliver poor sound quality and uncomfortably loud sounds. The challenge for manufacturers is to develop low-cost products with cosmetic appeal and appropriate electroacoustic characteristics.

Achieved Gain and Subjective Outcomes for a Wide-Bandwidth Contact Hearing Aid Fitted Using CAM2

Supplemental Digital Content is available in the text.

Objectives:

The objective of this study was to test the ability to achieve, maintain, and subjectively benefit from extended high-frequency amplification in a real-world use scenario, with a device that restores audibility for frequencies up to 10 kHz.

Design:

A total of 78 participants (149 ears) with mild to moderately-severe sensorineural hearing loss completed one of two studies conducted across eight clinical sites. Participants were fitted with a light-driven contact hearing aid (the Earlens system) that directly drives the tympanic membrane, allowing extended high-frequency output and amplification with minimal acoustic feedback. Cambridge Method for Loudness Equalization 2 - High Frequency (CAM2)-prescribed gains for experienced users were used for initial fitting, and adjustments were made when required according to participant preferences for loudness and comfort or when measures of functional gain (FG) indicated that more or less gain was needed. Participants wore the devices for an extended period. Prescribed versus adjusted output and gain, frequency-specific FG, and self-perceived benefit assessed with the Abbreviated Profile of Hearing Aid Benefit, and a custom questionnaire were documented. Self-perceived benefit results were compared with those for unaided listening and to ratings with participants’ own acoustic hearing aids.

Results:

The prescribed low-level insertion gain from 6 to 10 kHz averaged 53 dB across all ears, with a range from 26 to 86 dB. After adjustment, the gain from 6 to 10 kHz decreased to an average of 45 dB with a range from 16 to 86 dB. Measured FG averaged 39 dB from 6 to 10 kHz with a range from 11 to 62 dB. Abbreviated Profile of Hearing Aid Benefit results revealed a significant improvement in communication relative to unaided listening, averaging 28 to 32 percentage points for the background noise, reverberation, and ease of communication subscales. Relative to participants’ own hearing aids, the subscales ease of communication and aversiveness showed small but significant improvements for Earlens ranging from 6 to 7 percentage points. For the custom satisfaction questionnaire, most participants rated the Earlens system as better than their own hearing aids in most situations.

Conclusions:

Participants used and reported subjective benefit from the Earlens system. Most participants preferred slightly less gain at 6 to 10 kHz than prescribed for experienced users by CAM2, preferring similar gains to those prescribed for inexperienced users, but gains over the extended high frequencies were high relative to those that are currently available with acoustic hearing aids.

The maximum audible low-pass cutoff frequency for speech

Speech energy beyond 8 kHz is often audible for listeners with normal hearing. Limits to audibility in this frequency range are not well described. This study assessed the maximum audible low-pass cutoff frequency for speech, relative to full-bandwidth speech. The mean audible cutoff frequency was approximately 13 kHz, with a small but significant effect of talker sex. Better pure tone thresholds at extended high frequencies correlated with higher audible cutoff frequency. These findings demonstrate that bandlimiting speech even at 13 kHz results in a detectable loss for the average normal-hearing listener, suggesting there is information regarding the speech signal beyond 13 kHz.

Extended high-frequency hearing enhances speech perception in noise

Young healthy adults can hear tones up to at least 20 kHz. However, clinical audiometry, by which hearing loss is diagnosed, is limited at high frequencies to 8 kHz. Evidence suggests there is salient information at extended high frequencies (EHFs; 8 to 20 kHz) that may influence speech intelligibility, but whether that information is used in challenging listening conditions remains unknown. Difficulty understanding speech in noisy environments is the most common concern people have about their hearing and usually the first sign of age-related hearing loss. Digits-in-noise (DIN), a widely used test of speech-in-noise perception, can be sensitized for detection of high-frequency hearing loss by low-pass filtering the broadband masking noise. Here, we used standard and EHF audiometry, self-report, and successively higher cutoff frequency filters (2 to 8 kHz) in a DIN test to investigate contributions of higher-frequency hearing to speech-in-noise perception. Three surprising results were found. First, 74 of 116 "normally hearing," mostly younger adults had some hearing loss at frequencies above 8 kHz. Early EHF hearing loss may thus be an easily measured, preventive warning to protect hearing. Second, EHF hearing loss correlated with self-reported difficulty hearing in noise. Finally, even with the broadest filtered noise (≤8 kHz), DIN hearing thresholds were significantly better (P < 0.0001) than those using broadband noise. Sound energy above 8 kHz thus contributes to speech perception in noise. People with "normal hearing" frequently report difficulty hearing in challenging environments. Our results suggest that one contribution to this difficulty is EHF hearing loss.

The importance of a broad bandwidth for understanding "glimpsed" speech

When a target talker speaks in the presence of competing talkers, the listener must not only segregate the voices but also understand the target message based on a limited set of spectrotemporal regions ("glimpses") in which the target voice dominates the acoustic mixture. Here, the hypothesis that a broad audible bandwidth is more critical for these sparse representations of speech than it is for intact speech is tested. Listeners with normal hearing were presented with sentences that were either intact, or progressively "glimpsed" according to a competing two-talker masker presented at various levels. This was achieved by using an ideal binary mask to exclude time-frequency units in the target that would be dominated by the masker in the natural mixture. In each glimpsed condition, speech intelligibility was measured for a range of low-pass conditions (cutoff frequencies from 500 to 8000 Hz). Intelligibility was poorer for sparser speech, and the bandwidth required for optimal intelligibility increased with the sparseness of the speech. The combined effects of glimpsing and bandwidth reduction were well captured by a simple metric based on the proportion of audible target glimpses retained. The findings may be relevant for understanding the impact of high-frequency hearing loss on everyday speech communication.

Ecological cocktail party listening reveals the utility of extended high-frequency hearing

A fundamental principle of neuroscience is that each species' and individual's sensory systems are tailored to meet the demands placed upon them by their environments and experiences. What has driven the upper limit of the human frequency range of hearing? The traditional view is that sensitivity to the highest frequencies (i.e., beyond 8 kHz) facilitates localization of sounds in the environment. However, this has yet to be demonstrated for naturally occurring non-speech sounds. An alternative view is that, for social species such as humans, the biological relevance of conspecific vocalizations has driven the development and retention of auditory system features. Here, we provide evidence for the latter theory. We evaluated the contribution of extended high-frequency (EHF) hearing to common ecological speech perception tasks. We found that restricting access to EHFs reduced listeners' discrimination of talker head orientation by approximately 34%. Furthermore, access to EHFs significantly improved speech recognition under listening conditions in which the target talker's head was facing the listener while co-located background talkers faced away from the listener. Our findings raise the possibility that sensitivity to the highest audio frequencies fosters communication and socialization of the human species. These findings suggest that loss of sensitivity to the highest frequencies may lead to deficits in speech perception. Such EHF hearing loss typically goes undiagnosed, but is widespread among the middle-aged population.

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 review of the effects of unilateral hearing loss on spatial hearing

The capacity of the auditory system to extract spatial information relies principally on the detection and interpretation of binaural cues, i.e., differences in the time of arrival or level of the sound between the two ears. In this review, we consider the effects of unilateral or asymmetric hearing loss on spatial hearing, with a focus on the adaptive changes in the brain that may help to compensate for an imbalance in input between the ears. Unilateral hearing loss during development weakens the brain's representation of the deprived ear, and this may outlast the restoration of function in that ear and therefore impair performance on tasks such as sound localization and spatial release from masking that rely on binaural processing. However, loss of hearing in one ear also triggers a reweighting of the cues used for sound localization, resulting in increased dependence on the spectral cues provided by the other ear for localization in azimuth, as well as adjustments in binaural sensitivity that help to offset the imbalance in inputs between the two ears. These adaptive strategies enable the developing auditory system to compensate to a large degree for asymmetric hearing loss, thereby maintaining accurate sound localization. They can also be leveraged by training following hearing loss in adulthood. Although further research is needed to determine whether this plasticity can generalize to more realistic listening conditions and to other tasks, such as spatial unmasking, the capacity of the auditory system to undergo these adaptive changes has important implications for rehabilitation strategies in the hearing impaired.

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Unilateral hearing loss in infancy can disrupt spatial hearing, even after binaural inputs are restored.

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Plasticity in the developing brain enables substantial recovery in sound localization accuracy.

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Adaptation to unilateral hearing loss is based on reweighting of monaural spectral cues and binaural plasticity.

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Training on auditory tasks can partially compensate for unilateral hearing loss, highlighting potential therapies.

The Benefits of Increased Sensation Level and Bandwidth for Spatial Release From Masking

OBJECTIVE

Spatial release from masking (SRM) can increase speech intelligibility in complex listening environments. The goal of the present study was to document how speech-in-speech stimuli could be best processed to encourage optimum SRM for listeners who represent a range of ages and amounts of hearing loss. We examined the effects of equating stimulus audibility among listeners, presenting stimuli at uniform sensation levels (SLs), and filtering stimuli at two separate bandwidths.

DESIGN

Seventy-one participants completed two speech intelligibility experiments (36 listeners in experiment 1; all 71 in experiment 2) in which a target phrase from the coordinate response measure (CRM) and two masking phrases from the CRM were presented simultaneously via earphones using a virtual spatial array, such that the target sentence was always at 0 degree azimuth angle and the maskers were either colocated or positioned at ±45 degrees. Experiments 1 and 2 examined the impacts of SL, age, and hearing loss on SRM. Experiment 2 also assessed the effects of stimulus bandwidth on SRM.

RESULTS

Overall, listeners' ability to achieve SRM improved with increased SL. Younger listeners with less hearing loss achieved more SRM than older or hearing-impaired listeners. It was hypothesized that SL and bandwidth would result in dissociable effects on SRM. However, acoustical analysis revealed that effective audible bandwidth, defined as the highest frequency at which the stimulus was audible at both ears, was the best predictor of performance. Thus, increasing SL seemed to improve SRM by increasing the effective bandwidth rather than increasing the level of already audible components.

CONCLUSIONS

Performance for all listeners, regardless of age or hearing loss, improved with an increase in overall SL and/or bandwidth, but the improvement was small relative to the benefits of spatial separation.

Gender Identification Using High-Frequency Speech Energy: Effects of Increasing the Low-Frequency Limit

OBJECTIVE

The purpose of this study was to investigate the ability of normal-hearing listeners to use high-frequency energy for gender identification from naturally produced speech signals.

DESIGN

Two experiments were conducted using a repeated-measures design. Experiment 1 investigated the effects of increasing high-pass filter cutoff (i.e., increasing the low-frequency spectral limit) on gender identification from naturally produced vowel segments. Experiment 2 studied the effects of increasing high-pass filter cutoff on gender identification from naturally produced sentences. Confidence ratings for the gender identification task were also obtained for both experiments.

RESULTS

Listeners in experiment 1 were capable of extracting talker gender information at levels significantly above chance from vowel segments high-pass filtered up to 8.5 kHz. Listeners in experiment 2 also performed above chance on the gender identification task from sentences high-pass filtered up to 12 kHz.

CONCLUSIONS

Cumulatively, the results of both experiments provide evidence that normal-hearing listeners can utilize information from the very high-frequency region (above 4 to 5 kHz) of the speech signal for talker gender identification. These findings are at variance with current assumptions regarding the perceptual information regarding talker gender within this frequency region. The current results also corroborate and extend previous studies of the use of high-frequency speech energy for perceptual tasks. These findings have potential implications for the study of information contained within the high-frequency region of the speech spectrum and the role this region may play in navigating the auditory scene, particularly when the low-frequency portion of the spectrum is masked by environmental noise sources or for listeners with substantial hearing loss in the low-frequency region and better hearing sensitivity in the high-frequency region (i.e., reverse slope hearing loss).

Validating a Rapid, Automated Test of Spatial Release From Masking

PURPOSE

To evaluate the test-retest reliability of a headphone-based spatial release from a masking task with two maskers (referred to here as the SR2) and to describe its relationship to the same test done over loudspeakers in an anechoic chamber (the SR2A). We explore what thresholds tell us about certain populations (such as older individuals or individuals with hearing impairment) and discuss how the SR2 might be useful in the clinic.

METHOD

Fifty-four participants completed speech intelligibility tests in which a target phrase and two masking phrases from the Coordinate Response Measure corpus (Bolia, Nelson, Ericson, & Simpson, 2000) were presented either via earphones using a virtual spatial array or via loudspeakers in an anechoic chamber. For the SR2, the target sentence was always at 0° azimuth angle, and the maskers were either colocated at 0° or positioned at ± 45°. For the SR2A, the target was located at 0°, and the maskers were colocated or located at ± 15°, ± 30°, ± 45°, ± 90°, or ± 135°. Spatial release from masking was determined as the difference between thresholds in the colocated condition and each spatially separated condition. All participants completed the SR2 at least twice, and 29 of the individuals who completed the SR2 at least twice also participated in the SR2A. In a second experiment, 40 participants completed the SR2 8 times, and the changes in performance were evaluated as a function of test repetition.

RESULTS

Mean thresholds were slightly better on the SR2 after the first repetition but were consistent across 8 subsequent testing sessions. Performance was consistent for the SR2A, regardless of the number of times testing was repeated. The SR2, which simulates 45° separations of target and maskers, produced spatially separated thresholds that were similar to thresholds obtained with 30° of separation in the anechoic chamber. Over headphones and in the anechoic chamber, pure-tone average was a strong predictor of spatial release, whereas age only reached significance for colocated conditions.

CONCLUSIONS

The SR2 is a reliable and effective method of testing spatial release from masking, suitable for screening abnormal listening abilities and for tracking rehabilitation over time. Future work should focus on developing and validating rapid, automated testing to identify the ability of listeners to benefit from high-frequency amplification, smaller spatial separations, and larger spectral differences among talkers.

Light-Driven Contact Hearing Aid for Broad-Spectrum Amplification: Safety and Effectiveness Pivotal Study

Objective:

Demonstrate safety and effectiveness of the light-driven contact hearing aid to support FDA clearance.

Study Design:

A single-arm, open-label investigational-device clinical trial.

Setting:

Two private-practice and one hospital-based ENT clinics.

Patients:

Forty-three subjects (86 ears) with mild-to-severe bilateral sensorineural hearing impairment.

Intervention:

Bilateral amplification delivered via a light-driven contact hearing aid comprising a Tympanic Lens (Lens) with a customized platform to directly drive the umbo and a behind-the-ear sound processor (Processor) that encodes sound into light pulses to wirelessly deliver signal and power to the Lens.

Main Outcome Measures:

The primary safety endpoint was a determination of “no change” (PTA4 < 10 dB) in residual unaided hearing at the 120-day measurement interval. The primary efficacy endpoint was improvement in word recognition using NU-6 at the 30-day measurement interval over the baseline unaided case. Secondary efficacy endpoints included functional gain from 2 to 10 kHz and speech-in-noise improvement over the baseline unaided case using both omnidirectional and directional microphones.

Results:

The results for the 86 ears in the study determined a mean change of −0.40 dB in PTA4, indicating no change in residual hearing (p < 0.0001). There were no serious device- or procedure-related adverse events, or unanticipated adverse events. Word recognition aided with the Earlens improved significantly (p < 0.0001) over the unaided performance, by 35% rationalized arcsine units on average. Mean functional gain was 31 dB across 2 to 10 kHz. The average speech-recognition threshold improvement over the unaided case for the Hearing in Noise Test was 0.75 dB (p = 0.028) and 3.14 dB (p < 0.0001) for the omnidirectional and directional microphone modes, respectively.

Conclusion:

The safety and effectiveness data supported a de novo 510(k) submission that received clearance from the FDA.

Attenuating the ear canal feedback pressure of a laser-driven hearing aid

Microphone placement behind the pinna, which minimizes feedback but also reduces perception of the high-frequency pinna cues needed for sound localization, is one reason why hearing-aid users often complain of poor sound quality and difficulty understanding speech in noisy situations. In this paper, two strategies are investigated for minimizing the feedback pressure (thereby increasing the maximum stable gain, MSG) of a wide-bandwidth light-activated contact hearing aid (CHA) to facilitate microphone placement in the ear canal (EC): (1) changing the location of the drive force and its direction at the umbo, and (2) placing an acoustic damper within the EC to reduce the feedback pressure at the microphone location. The MSG and equivalent pressure output (EPO) are calculated in a 3D finite element model of a human middle ear based on micro computed tomography (micro-CT) images. The model calculations indicate that changing the umbo-force direction can decrease feedback pressure, but at the expense of decreased EPO. However the model shows improvements in MSG without sacrificing EPO when an acoustic damper is placed in the EC. This was verified through benchtop experimentation and in human cadaver temporal bones. The results pave the path towards a wide-bandwidth hearing aid that incorporates an EC-microphone design.