Excerpt: As expressed in published guidelines, there are several components to the overall hearing aid fitting process. The primary focus usually surrounds the selection of the hearing aids and their special features, verification of the fitting, and then some type of real-world validation. Another component recommended in all published hearing aid fitting guidelines but often overlooked, is pre-testing.

Question: I've been fitting a lot of receiver-in-canal (RIC) products, and when I have a patient with good low-frequency hearing, I like to use the smaller gain receiver option because I worry about the larger gain receiver being noisier. Sometimes though, use of the smaller gain receiver makes it difficult to fit prescriptive targets for moderately-severe to severe high frequency hearing loss thresholds. Should I be concerned about larger receivers being noisier?

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Background: Limited access of oral language caused by hearing loss poses a risk for the development of reading problems. A functional overlap in outcomes between children fit with hearing aids (HAs) and children provided with cochlear implants (CIs) results in a gray area in pediatric CI candidacy criteria. This gray area makes it more difficult to determine which device will provide the best developmental outcomes for children with borderline CI eligibility. Objective: In an effort to gain outcome data that could inform decision-making regarding CI versus HA candidacy, the question posed in this study concerned the speech intelligibility index (SII) levels of children with HAs that were comparable to children with CIs based upon reading outcomes of both groups. Methods: The study sample comprised of 77 children between the ages of 6;10 and 9;6 with hearing loss: 58 children with HAs and 19 children with CIs. Reading performance data was obtained using the Word Attack and Passage Comprehension subtests of the Woodcock Reading Mastery Tests. SII information was obtained for the HA group. To allow a comparison of reading performance relative to SII between children with CIs and children with HAs, multiple imputation was used to estimate a functional SII for the CI group based off the available reading information. Results: Children in the HA and CI groups demonstrated overall similar reading performance. The relationship between aided SII and reading in the HA group was found to be three times as large as that found for unaided PTA and reading. Children in the CI group were found to have reading abilities similar to children in the HA group with known SIIs of 0.73. Functional SII was imputed for the CI group with strong relative efficiency, but because confidence intervals were rather large, more data is needed in order to make statements with greater levels of confidence regarding implications for CI candidacy criteria.

Federal regulations specify that an employee working for eight hours cannot legally be exposed to noise which has a time-weighted average greater than 90 decibels on the A scale. The industrial workforce is comprised of not only people with normal hearing acuity, but of individuals who suffer from hearing loss. While current noise regulation standards are deemed appropriate for those with normal hearing, it is difficult to apply these standards to persons wearing hearing aids on the job. The ambient, or unamplified, noise levels that fall below the maximum permitted by OSHA standards may very well be amplified to levels greater than 90 dBA, by the hearing aid. If this were the case, the company employing the hearing aid user would technically be in violation of the OSHA regulations. This study addressed the question of what noise exposure might be expected for hearing aid users on the job in different situations, as well as in non-vocational settings. The research involved two methods, conducted to determine the noise levels created by hearing aids with different amounts of gain and to determine whether the amplified noise levels exceed those requiring intervention under current regulations. For both methods, ambient and amplified noise levels for each condition were gathered in specified increments, and were compared with regard to current regulatory standards. The resultant data revealed that when ambient noise levels average between 80 and 84 dBA, amplification provided by even a mild gain hearing aid caused the eight hour time-weighted averages (TWA's) to increase to levels above the 90 dBA maximum permissible levels as delineated by OSHA. Moderate and high gain aids further increased these levels. The results of this study suggest that the hearing aid users in industrial and perhaps non-industrial settings may very well be exposed to intensity levels which exceed OSHA maximums, even when ambient levels do not. The extent to which these arc exceeded are based on the gain and output of the hearing aid in use.

In order to help reduce hearing loss, the Occupational Safety and Health Administration regulates noise levels in work environments. However, hearing aids are the primary rehabilitative service provided for individuals with an occupational hearing loss. Very little is being done to monitor hearing aid use in the work environment. Noise which may be safe to an unaided ear can amplified to levels that are damaging to the ear when a hearing aid is being worn. However, it is necessary for some individuals to wear amplification in these noisy environments for safety reasons. As a consequence it is important that these individuals be able to understand speech in the presence of industrial noise while wearing amplification. The purpose of this study was to determine if there is a significant difference in speech intelligibility between linear hearing aids and different types of non-linear hearing aids when they are used in the presence of industrial noise. Twenty-four normal hearing subjects were selected for this study. Each subject was ask to identify words in four CID W-22 lists which had been recorded through a linear hearing aid and two different non-linear hearing aids. Test results showed significantly better word· recognition for the linear in quiet condition over all other conditions. Significantly higher scores were obtained for the TILL condition than were obtained for the Linear in noise and the BILL condition. These preliminary results suggest that an individual wearing amplification in a noisy work environment would benefit with a TILL circuit. The TILL circuit would provide better speech intelligibility in this type of environment. Therefore, providing a safer work environment for the hearing aid user.

Purpose: To study the impact of visual cues, speech materials and age on the frequency bandwidth necessary for optimizing speech recognition performance in listeners with normal hearing. Method: Speech recognition abilities of adults and children with normal hearing were assessed using three speech perception tests that were low-pass (LP) filtered and presented in quiet and noise. The speech materials included the Multimodal Lexical Sentence Test (MLST) that was presented in auditory-only and auditory-visual modalities for the purpose of determining the listener's visual benefit. In addition, The University of Western Ontario Plurals Test (UWO) assessed listeners' ability to detect high frequency acoustic information (e.g., /s/ and /z/) in isolated words and The Maryland CNC test that assessed speech recognition performance using isolated single words. Speech recognition performance was calculated as percent correct and was compared across groups (children and adults), tests (MLST, UWO, and CNC) and conditions (quiet and noise). Results: Statistical analyses revealed a number of significant findings. The effect of visual cues was significant in adults and children. The type of speech material had significant impact on the frequency bandwidth required for adults and children to optimize speech recognition performance. The children required significantly more bandwidth to optimize performance than adults across speech perception tests and conditions of quiet and noise. Adults and children required significantly more bandwidth in noise than in quiet across speech perception tests. Conclusion: The results suggest that children and adults require significantly less bandwidth for optimizing speech recognition performance when assessed using sentence materials which provide visual cues. Children, however, showed less benefit from visual cues in the noise condition than adults. The amount of bandwidth required by both groups decreased as a function of the speech material. In other words, the more ecologically valid the speech material (e.g., sentences with visual cues versus single isolated words), the less bandwidth was required for optimizing performance. In all, the optimal bandwidth (except for the noise condition of the UWO test) is achievable with current amplification schemes.

Hearing aid manufacturers commonly engineer automatic gain control (AGC) circuits which are aimed at reducing'sound tolerance problems and improving speech intelligibility among wearers. The most common type of AGC engineered is one utilizing a fast attack time. The present study was designed to evaluate the effects of both fast and slow attack times on the intelligibility of speech. Twenty-four normal hearing subjects listened to sixty pre-recorded sentences through two types of hearing aid circuits. Thirty sentences were modified by a fast attack AGC circuit, and thirty sentences were modified by a slow attack AGC. The subjects marked one of four multiple~choice answers for each sentence. The mean number of sentences answered incorrectly when heard through fast attack AGC was 8.25. When heard through slow attack AGC, the mean was 6.67. The performance differences which exist between these two modes of signal modification suggest that the fast attack does not improve intelligibility as significantly as slow attack time among normal listeners. Further investigation into the effects of slow attack AGC circuits on the user's ability to understand speech are recommended.

The early selection and use of an appropriate amplification system may be the most important aspect in the aural! rehabilitation of children who are hearing impaired. The main goal guiding the selection of hearing aids for children is to maximize their residual hearing through amplification in order to facilitate speech and language development. Seewald, Ross, and Stelmachciwicz (1987) have developed a speech-spectrum based procedure for selecting hearing aid characteristics for children referred to as the Desired Sensation Level Procedure (DSL) approach. This is an objective method which has been developed specifically for use with young pre-verbal children. I The purpose of the present study was to determine how closely the previously fitted amplification systems of profoundly hearing-impaired children approximated the amplification targets that would be prescribed for their hearing losses by the DSL method. The data were used to examine the feasibility and appropriateness of the DSL method for prescribing amplification for children with profound hearing impairments. Twenty amplification systems worn by profoundly hearing-impaired children were electroacoustically evaluated to discover how closely they approximated the DSL fitting criteria. Hearing thresholds were obtained for each subject for the frequencies 250, 500, 1000, 2000, and 4000 Hz using puretone audiometry. The DSL computer program was used to generate prescribed 2 cc. coupler targets at each frequency. The subjects' amplification systems were electroacoustically analyzed to determine the measured 2 cc. coupler response. Means and standard deviations were reported for prescribed and measured gain values at each frequency. Two-tailed t-tests were computed to determine if a difference exists between prescribed and measured gain. The tests were considered significant at the .05 level. A significant difference between the means was found at 2000 and 4000 Hz. Correlation coefficients were calculated at each frequency to determine if a predictable relationship between prescribed and measured gain existed. Correlation coefficients showed weak relationships between the two groups of data. These results showed the difficulty of meeting prescribed amplification targets, particularly in the high frequencies for children with profound hearing impairments.

As a group, children with hearing loss show slower language development than their peers with normal hearing. Age of intervention has a profound impact on language outcomes but data examining the correlation between degree of hearing loss and language outcomes are variable. Two approaches are used in the current study to examine this variability. In the first approach, we look at aided speech audibility as a potentially better predictor of communication outcomes than pure tone average. In the second approach, we look at a previously unexplored system in this population: working memory. We enrolled 16 children with mild to moderately-severe hearing loss (CMML) and 24 children with normal hearing (CNH) between 6 and 9 years of age into the study. Over two visits, participants underwent a battery of tests including measures of auditory perception, working memory, word learning, and vocabulary level. Parents completed questionnaires about their child's behavior and executive skills. Our results indicate that our measure of aided speech audibility, the aided Speech Intelligibility Index, was a stronger predictor than pure-tone average, spectral peak resolution, age of identification, age of intervention for word recognition score, nonword repetition score, and receptive vocabulary level. Our results showed little difference between CMML and CNH on measures of working memory including forward and backward digit span and phonological coding bias. We cannot make a strong recommendation for working memory intervention in CMML Reduced audibility causes the most devastating effects on word recognition and vocabulary development. Our results support the recommendation that audibility measures be performed on all children fit with hearing aids and that these measurements be used to flag children who may be at risk for delayed vocabulary acquisition.