Hearing Threshold Shifts Among 11- to 35-Year-Olds With Early Hearing Impairment.

OBJECTIVES: Data obtained from the clinical records of selected 11- to 35-year-olds with preadult onset hearing impairment were analyzed with 2 primary aims: (1) to determine the incidence of hearing threshold level (HTL) shift in this cohort and, (2) to examine the relationship between HTL shift, whole-of-life noise exposure, and other factors. DESIGN: Cross-sectional cohort study. Retrospective HTL + survey data for a sample of 237 young Australians receiving hearing (re)habilitation services were obtained. From these data, two subsets, (A) n = 127 and (B) n = 79, were analyzed. Participants with risk factors for progressive hearing loss (other than noise exposure) were excluded from both subsets. Subset (A) additionally excluded cochlear implant recipients, and subset (B) excluded cases with diagnosis of hearing loss after age 5 years. Using subset (A) data, the differences between final (recent) and specified baseline (initial) HTLs at 250, 500, 1000, 2000, and 4000 Hz were calculated and three criteria for HTL shift were applied. Correlations between reported noise exposure and HTL shift were calculated (Mann-Whitney U test). Using subset (B) data, relationships between high frequency (HF) HTL shift and exposure, and other personal and extrinsic factors were examined (Cox Regression model). Survival analyses (Kaplan-Meier) were performed to reveal the temporal pattern of HF shift. The magnitude of HF shifts at 5, 10, and 15 years post initial (i.e., specified baseline) audiogram were also calculated. RESULTS: For subset (A), HTL shift (≥15 dB any frequency, and/or ≥10 dB at two adjacent frequencies) was observed in 46.5% of cases examined. HF shift (≥15 dB at 2000 and/or 4000 Hz; one or both ears) was observed in 33.1% of cases. There was no relationship between HTL shift and reported whole-of-life exposure. For subset (B), no relationship was found between HF shift and noise exposure, nor 9 of 10 personal or extrinsic covariates tested. HF shift was significantly associated with HTL ≥ 70 dB at 2000 and/or 4000 Hz at initial audiogram. Survival analysis also illustrated that HF shift was more frequent, and occurred earlier, when HF hearing loss was ≥70 dB at initial audiogram. Median HF shifts at 15 years after initial audiogram were in the magnitude of 5 to 10 dB, and at the 90th percentile were 25 to 30 dB. CONCLUSIONS: HTL shift was observed in almost 50% of cases without predisposing factors for progressive hearing loss. The magnitude of HF shift increased gradually over time. While no relationship was found between HTL shift and noise exposure, the interpretation of this finding is restrained by the small spread of whole-of-life noise exposures, within a relatively conservative range. Nevertheless, this is the first direct examination of the relationship between HTL shift and noise exposure in young people with preadult hearing impairment.

Tinnitus and leisure noise.

OBJECTIVE: To study the relationship of life-time noise exposure and experience of tinnitus. DESIGN: Audiometric measures included otoscopy, pure tone air- and bone-conduction hearing threshold levels (HTL) and otoacoustic emissions (OAEs). Participants completed questionnaires including demographic information, past hearing health, history of participation in loud leisure activities, and attitudes to noise. STUDY SAMPLE: A representative sample (1435) of the young (11-35 years old) Australian population. RESULTS: Of the sample, 63% indicated they experienced tinnitus in some form. There was no correlation of tinnitus experience with HTL or OAE amplitudes. Although median octave band HTLs for those who experienced tinnitus "all the time" were slightly higher for those who did not, neither group exhibited HTLs outside clinically-normal values. Of those who experienced tinnitus a direct correlation was found between frequency of experience of tinnitus and increasing cumulative, life-time noise exposure. Those who experienced tinnitus were more likely to report noticing deterioration in their hearing ability over time and to report difficulty hearing in quiet and/or noisy situations. CONCLUSIONS: Experience of tinnitus was found throughout this young population but not associated with HTLs or variation in OAE amplitudes. Males experienced 'permanent' tinnitus at significantly greater rate than females.

Development of Telscreen: a telephone-based speech-in-noise hearing screening test with a novel masking noise and scoring procedure.

OBJECTIVE: In 2006 the National Acoustic Laboratories was commissioned to create a telephone-based hearing screening test. DESIGN: NAL developed 'Telscreen', a speech-in-noise test modelled on the Dutch and UK telephone tests. The first version, Telscreen I, had several novel features: individual scoring of digits; individual equalization of digit intelligibility; and accuracy-determined test termination. Evaluation of Telscreen I revealed that it did not discriminate satisfactorily between those with and without hearing impairment. Subsequently Telscreen II, which included a novel sensitized masking noise, was developed. STUDY SAMPLE: Telscreen I was evaluated by 105 participants (22-86 years), 37% with normal hearing (all thresholds <20 dB HL in the test ear), 63% with hearing impairment (all thresholds >20 dB HL in the test ear). Telscreen II was evaluated by 75 participants (25-86 years), 33% with normal hearing, 67% with hearing impairment. RESULTS: Correlations between Telscreen I results and hearing thresholds, r = 0.57, and hearing disability scores, r = 0.51 were highly significant, but lower than expected. Correlations for Telscreen II were higher: r = 0.77 and 0.65, respectively. Telscreen II was found to have high sensitivity: 90%; and specificity: 90.2%. CONCLUSIONS: Telscreen II is an efficient, reliable, and innovative hearing screening test that provides a solid foundation for future tests delivered via mobile and internet technologies.

TE and DP otoacoustic emission data from an Australian cross-sectional hearing study.

OBJECTIVE: This paper presents a summary of otoacoustic emission (OAE) data collected as part of an Australian hearing health survey ( Carter, 2011 ; Williams et al, 2014 ) designed to: (1) examine the relationship between audiological indicators and participant characteristics, and (2) extract audiological data suitable for reference use. DESIGN: Cross-sectional cohort study. Distortion product (DP) OAE and transient evoked (TE) OAE measures. STUDY SAMPLE: Age range 11-35 years; N = 1386 participants (2672 test ears). RESULTS: Descriptive statistics for amplitude and signal-to-noise ratio (SNR) were calculated for 327 participants (589 test ears; age 13 to 32 years). DPOAE amplitudes down to the 25th percentile were > 0 dB SPL for test frequencies up to 6 kHz. TEOAE SNRs down to the 25th percentile were > 6 dB SPL up to 4 kHz. SUMMARY: This dataset can be used as a clinical reference for similar populations, providing that the same test parameters are used. CONCLUSIONS: The clinical significance of OAE testing would be greater if agreed criteria were available. These data could be pooled with other datasets to build a substantial OAE database, similar to the existing international standards for pure-tone hearing threshold levels (HTLs) ( ISO, 2000 ).

Pure tone hearing thresholds and leisure noise: Is there a relationship?

This paper reports on the examination of the relationship between self-reported historical noise exposure during leisure activities and audiological indicators: Measured hearing threshold levels (HTLs) and otoacoustic emissions (OAEs). The research was conducted by a cross-sectional survey of 1,432 individuals whose ages ranged from 11 years to 35 years. Methodology included a comprehensive audiometric assessment including otoscopy, pure tone audiometry (PTA) (air- and bone-conduction), OAEs, and tympanometry. A comprehensive questionnaire gathered information on demographics, hearing health status, and participation in work, non-work, and leisure activities. Using the history of work, non-work, and leisure noise exposure, a cumulative lifetime noise exposure was estimated. No correlation was found between cumulative lifetime noise exposure and audiometric PTA or OAE parameters.

The leisure-noise dilemma: hearing loss or hearsay? What does the literature tell us?

The authors undertook a review of the literature, focussing on publications describing the following: (1) Pure tone threshold data for adolescents/young adults; (2) Measurements/estimates of noise exposure from leisure activities; and (3) The relationship between hearing threshold levels (HTLs) and leisure-noise exposure. There is a large volume of published materials relevant to these topics, and opinion among authors regarding the relationship between leisure-noise exposure and HTLs varies significantly. At one extreme is the view that the effects of leisure-noise are minimal. The opposing belief is that as a direct result of leisure-noise exposure, significant HTL shifts and possibly significant hearing disability are occurring in a large (and increasing) proportion of young people. It has been claimed that behaviors relating to leisure-noise are "as threatening to young people's health as more traditional risk behaviors" (, p. 55). This view has been reiterated by the popular media. This review revealed that while sufficient data confirm that some leisure pursuits provide potentially hazardous noise levels, the nature of the exposure-injury relationship for leisure-noise is yet to be determined. Specific information about the quality-of-life effects of threshold shift related to leisure-noise exposure is also lacking. The scope and limitations of a large sample of relevant publications and an overview of the methodological issues in this area of research are briefly presented. Considerations for future research are raised.

The relationship between cortical auditory evoked potential (CAEP) detection and estimated audibility in infants with sensorineural hearing loss.

OBJECTIVE: To determine the effectiveness of objective statistical detection in CAEP testing to evaluate audibility in young infants with sensorineural hearing loss. DESIGN: CAEP recordings to speech-based stimuli were made at three presentation levels (55, 65, or 75 dB SPL) when a group of hearing-impaired infants were either aided or unaided. Later-obtained behavioral audiograms were used as the gold standard against which to evaluate the accuracy of the automatic detection of the presence/absence of CAEP responses. STUDY SAMPLE: Participants were 18 infants with confirmed sensorineural hearing loss. RESULTS: Higher sensation levels led to a greater number of present CAEP responses being detected. More CAEP waveforms were detected in the aided condition than in the unaided condition. CONCLUSION: Our results suggest that the presence/absence of CAEP responses defined by the automatic statistical criterion was effective in showing whether increased sensation levels provided by amplification were sufficient to reach the cortex. This was clearly apparent from the significant increase in cortical detections when comparing unaided with aided testing.

Music to whose ears? The effect of social norms on young people's risk perceptions of hearing damage resulting from their music listening behavior.

Professional and community concerns about the potentially dangerous noise levels for common leisure activities has led to increased interest on providing hearing health information to participants. However, noise reduction programmes aimed at leisure activities (such as music listening) face a unique difficulty. The noise source that is earmarked for reduction by hearing health professionals is often the same one that is viewed as pleasurable by participants. Furthermore, these activities often exist within a social setting, with additional peer influences that may influence behavior. The current study aimed to gain a better understanding of social-based factors that may influence an individual's motivation to engage in positive hearing health behaviors. Four hundred and eighty-four participants completed questionnaires examining their perceptions of the hearing risk associated with listening to music listening and asking for estimates of their own and their peer's music listening behaviors. Participants were generally aware of the potential risk posed by listening to personal stereo players (PSPs) and the volumes likely to be most dangerous. Approximately one in five participants reported using listening volumes at levels perceived to be dangerous, an incidence rate in keeping with other studies measuring actual PSP use. However, participants showed less awareness of peers' behavior, consistently overestimating the volumes at which they believed their friends listened. Misperceptions of social norms relating to listening behavior may decrease individuals' perceptions of susceptibility to hearing damage. The consequences of hearing health promotion are discussed, along with suggestions relating to the development of new programs.

Spatial release from masking in normal-hearing children and children who use hearing aids.

Listening to speech in competing sounds poses a major difficulty for children with impaired hearing. This study aimed to determine the ability of children (3-12 yr of age) to use spatial separation between target speech and competing babble to improve speech intelligibility. Fifty-eight children (31 with normal hearing and 27 with impaired hearing who use bilateral hearing aids) were assessed by word and sentence material. Speech reception thresholds (SRTs) were measured with speech presented from 0° azimuth, and competing babble from either 0° or ±90° azimuth. Spatial release from masking (SRM) was defined as the difference between SRTs measured with co-located speech and babble and SRTs measured with spatially separated speech and babble. On average, hearing-impaired children attained near-normal performance when speech and babble originated from the frontal source, but performed poorer than their normal-hearing peers when babble was spatially separated from target speech. On average, normal-hearing children obtained an SRM of 3 dB whereas children with hearing loss did not demonstrate SRM. Results suggest that hearing-impaired children may need enhancement in signal-to-noise ratio to hear speech in difficult listening conditions as well as normal-hearing children.

The detection of infant cortical auditory evoked potentials (CAEPs) using statistical and visual detection techniques.

BACKGROUND: With the advent of newborn hearing screening programs, the need to verify the fit of hearing aids in young infants has increased. The recording of cortical auditory evoked potentials (CAEPs) for this purpose is quite feasible, but rapid developmental changes that affect response morphology and the presence of electrophysiological noise can make subjective response detection challenging. PURPOSE: The purpose of this study was to investigate the effectiveness of an automated statistic versus experienced examiners in detecting the presence of infant CAEPs when stimuli were present and reporting the absence of CAEPs when no stimuli were present. RESEARCH DESIGN: A repeated-measures design was used where infant-generated CAEPs were interpreted by examiners and an automated statistic. STUDY SAMPLE: There were nine male and five female infants (mean age, 12 mo; SD, 3.4) who completed behavioral and electrophysiological testing using speech-based stimuli. DATA COLLECTION AND ANALYSIS: In total, 87 infant CAEPs were recorded to three sensation levels, 10, 20 and 30 dB relative to the behavioral thresholds and to nonstimulus trials. Three examiners were presented with these responses: (1) "in series," where waveforms were presented in order of decreasing stimulus presentation levels, and (2) "nonseries," where waveforms were randomized completely and presented as independent waveforms. The examiners were given no information about the stimulus levels and were asked to determine whether responses to auditory stimulation could be observed and their degree of certainty in making their decision. Data from the CAEP responses were also converted to multiple dependent variables and analyzed using Hotelling's T(2). Results from both methods of response detection were analyzed using a repeated measures ANOVA (analysis of variance) and parameters of signal detection theory known as d-prime (d') and the area under the receiver operating characteristic (ROC) curve. RESULTS: Results showed that as the stimulus level increased, the sensitivity index, d', increased for both methods of response detection, but neither reached the maximum possible d' value with a sensation level of 30 dB. The examiners with the greatest experience and Hotelling's T(2) were equally sensitive in differentiating the CAEP from noise. CONCLUSIONS: Hotelling's T(2) appears to detect CAEPs from normal hearing infants at a rate equal to that of an experienced examiner. A clinical instrument that applies Hotelling's T(2) on-line, so that the likelihood of response detection can be assessed objectively, should be of particular benefit to the novice or less experienced examiner.

The detection of adult cortical auditory evoked potentials (CAEPs) using an automated statistic and visual detection.

The detection of adult cortical auditory evoked potentials (CAEPs) can be challenging when the stimulus is just audible. The effectiveness of a statistic compared with expert examiners in (1) detecting the presence of CAEPs when stimuli were present, and (2) reporting the absence of CAEPs when no stimuli were present, was investigated. CAEPs recorded from ten adults, using two speech-based stimuli, five stimulus presentation levels, and non-stimulus conditions, were given to four experienced examiners who were asked to determine if responses to auditory stimulation could be observed, and their degree of certainty in making their decision. These recordings were also converted to multiple dependent variables and Hotelling's T2 was applied to calculate the probability that the mean value of any linear combination of these variables was significantly different from zero. Results showed that Hotelling's T2 was equally sensitive to the best of individual experienced examiners in differentiating a CAEP from random noise. It is reasonable to assume that the difference in response detection for a novice examiner and Hotelling's T2 would be even greater.

Variation in preferred gain with experience for hearing-aid users.

This study aimed to determine whether gain adaptation occurs, and at which frequency bands, among new hearing aid (HA) users. Fifty new and 26 experienced HA users were fitted with three listening programs (NAL-NL1 and NAL-NL1 with low- and high-frequency cuts) in the same hearing instrument family. Real-life gain preferences and comfortable loudness levels were measured one, four, and 13 months post-fitting for the new HA users, and one month post-fitting for the experienced HA users. Relative to experienced HA users, new HA users preferred progressively less overall gain than prescribed as the hearing loss became more severe. Gain adaptation occurred in new HA users with greater hearing loss, but was not complete 13 months post-fitting, and was not explained by changes in loudness perception. Preferences for a high-frequency gain cut by half of all study participants could not be predicted from audiological data. Gain adaptation management is recommended for new HA users with more than a mild hearing loss.

Long-term usage of modern signal processing by listeners with severe or profound hearing loss: a retrospective survey.

PURPOSE: To investigate the long-term benefit of multichannel wide dynamic range compression (WDRC) alone and in combination with directional microphones and noise reduction/speech enhancement for listeners with severe or profound hearing loss. METHOD: At the conclusion of a research project, 39 participants with severe or profound hearing loss were fitted with WDRC in one program and WDRC with directional microphones and speech enhancement enabled in a 2nd program. More than 2 years after the 1st participants exited the project, a retrospective survey was conducted to determine the participants' use of, and satisfaction with, the 2 programs. RESULTS: From the 30 returned questionnaires, it seems that WDRC is used with a high degree of satisfaction in general everyday listening situations. The reported benefit from the addition of a directional microphone and speech enhancement for listening in noisy environments was lower and varied among the users. This variable was significantly correlated with how much the program was used. CONCLUSIONS: The less frequent and more varied use of the program with directional microphones and speech enhancement activated in combination suggests that these features may be best offered in a 2nd listening program for listeners with severe or profound hearing loss.

Preferred low- and high-frequency compression ratios among hearing aid users with moderately severe to profound hearing loss.

This study aimed to determine the low- and high-frequency compression ratios of a fast-acting device that were preferred by people with moderately severe to profound hearing loss. Three compression ratios (1:1, 1.8:1, and 3:1) were combined in the low and high frequencies to produce nine schemes that were evaluated pair-wise for three weeks in the field using an adaptive procedure. The evaluation was performed by 21 experienced hearing aid users with a moderately severe to profound hearing loss. Diaries and an exit interview were used to monitor preferences. Generally, the subjects preferred lower compression ratios than are typically prescribed, especially in the low frequencies. Specifically, 11 subjects preferred linear amplification in the low frequencies, and 14 subjects preferred more compression in the high than in the low frequencies. Preferences could not be predicted from audiometric data, onset of loss, or past experience with amplification. The data suggest that clients with moderately severe to profound hearing loss should be fitted with low-frequency compression ratios in the range 1:1 to 2:1 and that fine-tuning is essential.

More to Lose? Noise-Risk Perceptions of Young Adults with Hearing Impairment.

This study investigated the attitudes and behaviors of young adults with hearing impairment (HI), in relation to leisure noise. It was hypothesized that young people with HI would have more negative perceptions of noise exposure than their peers with nonimpaired (normal) hearing (NH) and would engage more frequently in self-protective behaviors. Questionnaires were administered as part of a larger study of young Australians with: (1) preadult onset HI and (2) NH. Data from adults (age range 18 to 24 years; n = 79 with HI, n = 131 with NH) were selected for the current analysis. Attitudes data for HI and NH groups were compared using chi-square tests, and the reported use of hearing aids and personal hearing protectors (PHPs) in leisure environments was quantified. Most participants with HI and NH regarded leisure noise as a health hazard but rated their own noise-injury risk as lower than that of their peer group. The use of PHPs was low overall, and many participants with HI reported using hearing aids (switched on) during noisy leisure activities. An equal and substantial proportion of participants with HI and NH reported dislike and avoidance of loud activities. Systematic noise management in leisure environments would address noise-injury risk and also enhance social participation.

An Estimation of the Whole-of-Life Noise Exposure of Adolescent and Young Adult Australians with Hearing Impairment.

BACKGROUND: Since amplified music gained widespread popularity, there has been community concern that leisure-noise exposure may cause hearing loss in adolescents and young adults who would otherwise be free from hearing impairment. Repeated exposure to personal stereo players and music events (e.g., nightclubbing, rock concerts, and music festivals) are of particular concern. The same attention has not been paid to leisure-noise exposure risks for young people with hearing impairment (either present from birth or acquired before adulthood). This article reports on the analysis of a subset of data (leisure participation measures) collected during a large, two-phase study of the hearing health, attitudes, and behaviors of 11- to 35-yr-old Australians conducted by the National Acoustic Laboratories (n = 1,667 hearing threshold level datasets analyzed). The overall aim of the two-phase study was to determine whether a relationship between leisure-noise exposure and hearing loss exists. PURPOSE: In the current study, the leisure activity profiles and accumulated ("whole-of-life") noise exposures of young people with (1) hearing impairment and (2) with normal hearing were compared. RESEARCH DESIGN: Cross-sectional cohort study. STUDY SAMPLE: Hearing impaired (HI) group, n = 125; normal (nonimpaired) hearing (NH) group, n = 296, analyzed in two age-based subsets: adolescents (13- to 17-yr-olds) and young adults (18- to 24-yr-olds). DATA COLLECTION AND ANALYSIS: Participant survey. The χ² test was used to identify systematic differences between the leisure profiles and exposure estimates of the HI and NH groups. Whole-of-life noise exposure was estimated by adapting techniques described in ISO 1999. RESULTS: For adolescents, leisure profiles were similar for the two groups and few individuals exceeded the stated risk criterion. For young adults, participation was significantly lower for the HI group for 7 out of 18 leisure activities surveyed. Activity diversity and whole-of-life exposure were also significantly lower for the HI group young adults. A substantial number of individuals in both groups reported participation in leisure activities known to involve high noise levels (HI < NH). The individual whole-of-life exposures for the HI and NH participants were estimated and group median exposures were calculated. The median exposure for HI group young adults was significantly lower than that for the NH group (710 versus 1,615 Pa² h [Pascal squared hours]). CONCLUSIONS: The number of young adults with estimated exposure above the chosen noise-risk criterion in the NH group is concerning. With respect to the goals of hearing loss prevention initiatives, the more conservative social behavior (e.g., less nightclubbing) observed among HI group young adults may be regarded as a positive finding, but it could also signify relative social disadvantage for some young adults with hearing impairment.

Clinical Experience of Using Cortical Auditory Evoked Potentials in the Treatment of Infant Hearing Loss in Australia.

This article presents the clinical protocol that is currently being used within Australian Hearing for infant hearing aid evaluation using cortical auditory evoked potentials (CAEPs). CAEP testing is performed in the free field at two stimulus levels (65 dB sound pressure level [SPL], followed by 55 or 75 dB SPL) using three brief frequency-distinct speech sounds /m/, /É¡/, and /t/, within a standard audiological appointment of up to 90 minutes. CAEP results are used to check or guide modifications of hearing aid fittings or to confirm unaided hearing capability. A retrospective review of 83 client files evaluated whether clinical practice aligned with the clinical protocol. It showed that most children could be assessed as part of their initial fitting program when they were identified as a priority for CAEP testing. Aided CAEPs were most commonly assessed within 8 weeks of the fitting. A survey of 32 pediatric audiologists provided information about their perception of cortical testing at Australian Hearing. The results indicated that clinical CAEP testing influenced audiologists' approach to rehabilitation and was well received by parents and that they were satisfied with the technique. Three case studies were selected to illustrate how CAEP testing can be used in a clinical environment. Overall, CAEP testing has been effectively integrated into the infant fitting program.

Cortical auditory-evoked potentials (CAEPs) in adults in response to filtered speech stimuli.

BACKGROUND: Previous studies have demonstrated that cortical auditory-evoked potentials (CAEPs) can be reliably elicited in response to speech stimuli in listeners wearing hearing aids. It is unclear, however, how close to the aided behavioral threshold (i.e., at what behavioral sensation level) a sound must be before a cortical response can reliably be detected. PURPOSE: The purpose of this study was to systematically examine the relationship between CAEP detection and the audibility of speech sounds (as measured behaviorally), when the listener is wearing a hearing aid fitted to prescriptive targets. A secondary aim was to investigate whether CAEP detection is affected by varying the frequency emphasis of stimuli, so as to simulate variations to the prescribed gain-frequency response of a hearing aid. The results have direct implications for the evaluation of hearing aid fittings in nonresponsive adult clients, and indirect implications for the evaluation of hearing aid fittings in infants. RESEARCH DESIGN: Participants wore hearing aids while listening to speech sounds presented in a sound field. Aided thresholds were measured, and cortical responses evoked, under a range of stimulus conditions. The presence or absence of CAEPs was determined by an automated statistic. STUDY SAMPLE: Participants were adults (6 females and 4 males). Participants had sensorineural hearing loss ranging from mild to severe-profound in degree. DATA COLLECTION AND ANALYSIS: Participants' own hearing aids were replaced with a test hearing aid, with linear processing, during assessments. Pure-tone thresholds and hearing aid gain measurements were obtained, and a theoretical prediction of speech stimulus audibility for each participant (similar to those used for audibility predictions in infant hearing aid fittings) was calculated. Three speech stimuli, (/m/, /t/, and /g/) were presented aided (monaurally, nontest ear occluded), free field, under three conditions (+4 dB/octave, -4 dB/octave, and without filtering), at levels of 40, 50, and 60 dB SPL (measured for the unfiltered condition). Behavioral thresholds were obtained, and CAEP recordings were made using these stimuli. The interaction of hearing loss, presentation levels, and filtering conditions resulted in a range of CAEP test behavioral sensation levels (SLs), from -25 to +40 dB. RESULTS: Statistically significant CAEPs (p < .05) were obtained for virtually every presentation where the behavioral sensation level was >10 dB, and for only 5% of occasions when the sensation level was negative. In these ("false-positive") cases, the greatest (negative) sensation level at which a CAEP was judged to be present was -6 dB SL. CONCLUSIONS: CAEPs are a sensitive tool for directly evaluating the audibility of speech sounds, at least for adult listeners. CAEP evaluation was found to be more accurate than audibility predictions, based on threshold and hearing aid response measures.

Sensitivity of cortical auditory evoked potential detection for hearing-impaired infants in response to short speech sounds.

Cortical auditory evoked potentials (CAEPs) are an emerging tool for hearing aid fitting evaluation in young children who cannot provide reliable behavioral feedback. It is therefore useful to determine the relationship between the sensation level of speech sounds and the detection sensitivity of CAEPs, which is the ratio between the number of detections and the sum of detections and non-detections. Twenty-five sensorineurally hearing impaired infants with an age range of 8 to 30 months were tested once, 18 aided and 7 unaided. First, behavioral thresholds of speech stimuli /m/, /g/, and /t/ were determined using visual reinforcement orientation audiometry. Afterwards, the same speech stimuli were presented at 55, 65, and 75 dB sound pressure level, and CAEPs were recorded. An automatic statistical detection paradigm was used for CAEP detection. For sensation levels above 0, 10, and 20 dB respectively, detection sensitivities were equal to 72±10, 75±10, and 78±12%. In 79% of the cases, automatic detection P-values became smaller when the sensation level was increased by 10 dB. The results of this study suggest that the presence or absence of CAEPs can provide some indication of the audibility of a speech sound for infants with sensorineural hearing loss. The detection of a CAEP might provide confidence, to a degree commensurate with the detection probability, that the infant is detecting that sound at the level presented. When testing infants where the audibility of speech sounds has not been established behaviorally, the lack of a cortical response indicates the possibility, but by no means a certainty, that the sensation level is 10 dB or less.

NAL-NL2 empirical adjustments.

NAL-NL1, the first procedure from the National Acoustic Laboratories (NAL) for prescribing nonlinear gain, was a purely theoretically derived formula aimed at maximizing speech intelligibility for any input level of speech while keeping the overall loudness of speech at or below normal loudness. The formula was obtained through an optimization process in which speech intelligibility and loudness were predicted from selected models. Using updated models and applying some revisions to the derivation process, a theoretically derived NAL-NL2 formula was obtained in a similar way. Further adjustments, directed by empirical data collected in studies using NAL-NL1 as the baseline response, have been made to the theoretically derived formula. Specifically, empirical data have demonstrated that (a) female hearing aid users prefer lower overall gain than male users; (b) new hearing aid users with more than a mild hearing loss prefer increasingly less gain with increasing degree of hearing loss than experienced hearing aid users, and require up to 2 years to adapt to gain levels selected by experienced hearing aid users; (c) unilaterally and bilaterally fitted hearing aid users prefer overall gain levels that vary less than estimated by the bilateral correction factor; (d) adults prefer lower overall gain than children; and (e) people with severe/profound hearing loss prefer lower compression ratios than predicted when fitted with fast-acting compression. The literature and data leading to these conclusions are summarized and discussed in this article, and the procedure for implementing the adjustments to the theoretically derived NAL-NL2 formula is described.