Hearing Aid Fitting Procedures Research Articles

A Retrospective Study of Bimodal Benefits of Cochlear Implant Children

Purpose: Bimodal children showed various improvements in speech, language, and music perception. The purpose of this study is to investigate bimodal benefits and bimodal hearing aid fitting of cochlear implant children with a retrospective chart review.Methods: A total of 44 charts of cochlear implant children were retrospectively reviewed in this study. Hearing thresholds, word recognition scores, and hearing aid fitting procedures were reviewed and summarized.Results: Bimodal children showed 4%points improvements in word recognition scores and 30~40 gains across frequencies with hearing aids. For bimodal hearing aid fitting, all children used desired sensation level v5 fitting formula with wide frequency bands. Real ear measurements were performed to match with targets and loudness balancing across ears was also conducted. Hearing thresholds with and without hearing aids were not correlated with word recognition scores in bimodal condition.Conclusion: Bimodal children showed improved hearing thresholds with hearing aids and little bimodal benefits in word recognition tests. Additional protocols including speech in noise tests, subjective questionnaires are recommended to evaluate bimodal benefits.

A Study on the Preferred Real-Ear Insertion Gain of Multi-Channel Hearing Aid for the Korean with Sensorineural Hearing Loss

Purpose: This study aimed to compare the preferred real-ear insertion gain for Korean (PREIG-K) wearing multi-channel hearing aid with the National Acoustics Laboratories-Non-Linear version 2 (NAL-NL2; National Acoustic Laboratories) gains in order to develop Korean hearing aid fitting formula.Methods: A total of thirty one (62 ears) Korean hearing aid users were included in this study. All subjects wore in-the-canal or custom hearing aids in both ears. Individual hearing aid fitting procedures involved to adjust the gains for 50, 65, and 80 dB sound pressure level of speech across low, high, and wideband frequency bands based on participant’s subjective responses. In addition, only the high frequency bands of 1 kHz or more of the PREIG-K were re-adjusted to be the same as NAL-NL2 gain and then the word recognition scores (WRSs) were compared before and after the adjusting gain. Results: The results showed that the PREIG-K increased up to 1.5 kHz with the maximum amount, then the PREIG-K decreased across the frequencies. For all half octave frequencies, the PREIG-Ks were substantially less than the NAL-NL2. When the PREIG-K of high frequencies were re-adjusted same as the NAL-NL2 gains, the WRSs of the PREIG-K were not significantly different before and after gain adjustment. The slopes up to 1.5 kHz frequencies of the PREIG-K were steeper than the slopes of NAL-NL2 gain, however similar to the slope of manufactures’ fitting formulae.Conclusion: The development of an effective hearing aid fitting formula for improving the communication abilities of hearing-impaired Korean will require further experiments considering the language, physical characteristics, and word recognition used by Koreans.

Comparing the Effect of Different Hearing Aid Fitting Methods in Bimodal Cochlear Implant Users

Purpose The aim of the study was to investigate the effect of 3 hearing aid fitting procedures on provided gain of the hearing aid in bimodal cochlear implant users and their effect on bimodal benefit. Method This prospective study measured hearing aid gain and auditory performance in a cross-over design in which 3 hearing aid fitting methods were compared. Hearing aid fitting methods differed in initial gain prescription rule (NAL-NL2 and Audiogram+) and loudness balancing method (broadband vs. narrowband loudness balancing). Auditory functioning was evaluated by a speech-in-quiet test, a speech-in-noise test, and a sound localization test. Fourteen postlingually deafened adult bimodal cochlear implant users participated in the study. Results No differences in provided gain and in bimodal performance were found for the different hearing aid fittings. For all hearing aid fittings, a bimodal benefit was found for speech in noise and sound localization. Conclusion Our results confirm that cochlear implant users with residual hearing in the contralateral ear substantially benefit from bimodal stimulation. However, on average, no differences were found between different types of fitting methods, varying in prescription rule and loudness balancing method.

How to Optimally Fit a Hearing Aid for Bimodal Cochlear Implant Users: A Systematic Review.

Bimodal hearing has shown to improve speech recognition in quiet and in noise and to improve sound localization compared with unilateral cochlear implant (CI) use alone. Fitting the CI and hearing aid (HA) separately has been described well, but HA fitting procedures for bimodal CI users are not well researched or widely accepted. The aim of the present study was to systematically review the literature on the effect of different HA fitting strategies on auditory performance in bimodal CI users. Original articles, written in English, were identified through systematic searches in Medline (OvidSP), Embase, Web of Science, Scopus, CINAHL, Cochrane, PubMed publisher, and Google Scholar. The quality of the studies was assessed on five aspects: methodologic quality (with the methodological index for nonrandomized studies score), number of subjects, quality of the description of contralateral hearing loss, quality of HA verification, and direct comparison of HA fitting procedures based on auditory performance. A total of 1665 records were retrieved, of which 17 were included for systematical reviews. Critical appraisal led to three high-quality studies, 10 medium-quality studies, and four low-quality studies. The results of the studies were structured according to four topics: frequency response, frequency translation/transposition, dynamic range compression, and loudness. In general, a bimodal benefit was found in most studies, using various strategies for the HA fitting. Using a standard prescription rule such as National Acoustics Laboratory formula-non-linear 1, National Acoustics Laboratory formula-non-linear 2, or desired sensation level is a good starting point in children and adults. Although a bimodal benefit was found in most studies, there is no clear evidence how certain choices in HA fitting contribute to optimal bimodal performance. A generally accepted HA prescription rule is an essential part of most fitting procedures used in the studies. Current evidence suggests that frequency lowering or transposition is not beneficial. Individual fine tuning based on loudness or general preference is often applied, but its additional value for auditory performance should be investigated more thoroughly. Good quality comparative studies are needed to further develop evidence-based fitting procedures in case of bimodal listening.

Teleaudiology Services for Rehabilitation With Hearing Aids in Adults: A Systematic Review

This review examined (a) the current evidence from studies on teleaudiology applications for rehabilitation of adults with hearing impairment with hearing aids and (b) whether it is sufficient to support the translation into routine clinical practice. A search strategy and eligibility criteria were utilized to include articles specifically related to hearing aid fitting and follow-up procedures that are involved in consultations for the rehabilitation of adults, where the service was provided by the clinician by teleaudiology. A search using key words and Medical Subject Headings (MeSH) was conducted on the main electronic databases that index health-related studies. The included studies were assessed using validated evaluation tools for methodological quality, level of evidence, and grade recommendations for application into practice. Fourteen studies were identified as being within the scope of this review. The evaluation tools showed that none of these studies demonstrated either a strong methodological quality or high level of evidence. Analysis of evidence identified 19 activities, which were classified into service outcomes categories of feasibility, barriers, efficiency, quality, and effectiveness. Recommendations could be made regarding the (a) feasibility, (b) barriers, and (c) efficiency of teleaudiology for the rehabilitation of hearing loss with hearing aids. This review provides up-to-date evidence for teleaudiology hearing aid services in new and experienced hearing aid users in different practice settings. Findings direct future research priorities to strengthen evidence-based practice. There is a need for further studies of many aspects of teleaudiology services for rehabilitation with hearing aids to support their implementation into clinical practice. https://doi.org/10.23641/asha.6534473.

Application of Data Mining to a Large Hearing-Aid Manufacturer's Dataset to Identify Possible Benefits for Clinicians, Manufacturers, and Users.

Modern hearing instruments contain logging technology to record data, such as the acoustic environments in which the device is being used and how the signal processing is consequently operating. Combined with patient data, such as the audiogram, this information gives a more comprehensive picture of the user and their relationship with the aid. Here, a relatively large, anonymized dataset (>300,000 devices, >150,000 wearers) from a hearing-aid manufacturer was data mined for connections between subsets of the logged varieties of data. Apart from replicating links that have previously been reported in labor-intensive studies, a link between device style (in-the-ear/behind-the-ear) and the sound levels of encountered environments was demonstrated, suggesting that some device types are more successful from a lifestyle perspective. Furthermore, the data also suggested links between the audiogram and the sound environments in which the aid was operated. Modeling the expected link between the environment and the microphone directionality settings revealed patterns of either abnormal fitting or where the aid was not operating correctly—factors that may indicate a failed fitting. Given the necessarily redacted nature of the dataset, the reported findings represent a proof-of-concept of the use of relatively large-scale data mining to guide and assess hearing-aid fitting procedures for possible benefits to the clinician, manufacturer, and patient.

Long term average speech spectra of Turkish

Long-term average speech spectra (LTASS) are a voice analysis method that is recommended to be used in various areas, such as hearing aid fittings, automatic speaker recognition and voice disorders. Evaluations of LTASS in different languages have been published; however, this analysis has not been conducted for the Turkish. Therefore, the first aim of this study was to conduct this analysis, generate normative values and compare the obtained LTASS curve for the Turkish with those obtained for other languages reported in the literature. To achieve this objective, 40 adults with healthy hearing and speech characteristics were evaluated. Long-term spectral shape is presented in a graphical form, with visual comparisons to other research findings. Spectral differences by gender were analyzed, with statistically significant differences observed between gender groups and overall LTASS. The LTASS curve for the Turkish is similar to those reported for other languages, but there are also observable differences. Use of generated speech signals in hearing aid fitting procedures is recommended.

補聴器の進歩と聴覚医学

要旨: 補聴器を個々の難聴者に適合するように設定していく方法について概説した。 大きく比較選択法と規定選択法という二つの手順が存在するが通常の臨床では両者が併用されている。 規定選択法はハーフゲインルールに始まりその後補聴器性能の進歩に伴って数多くの方法が発表されてきたが, 現在では NAL-NL 法と DSL 法が広く用いられている。 両方法の補聴効果を比較した研究の結果では語音明瞭度の成績では差はみられていないが DSL 処方の方が利得は大きい。 これらの規定選択法で示されるターゲットは基本的には最終的な設定への指標と考えるべきで新規の装用者ではそれより小さな利得から徐々に上げていく方法が提案されている。 欧米で開発されたこれらの処方ターゲットが英語とは音響的特徴が異なる日本語においても妥当であるかどうかについては今後検討する必要があると思われる。

Electroencephalographic estimates of listening effort for hearing aid fitting

Objective estimates of listening effort could support hearing aid fitting procedures. For this reason, we have analyzed neural correlates of listening effort using electroencephalographic methods and quantitative neurofunctional modeling in recent years. In particular, we have developed a neurophysical corticothalamic feedback model for electroencephalographic listening effort correlates in event-related potentials (ERP), which allowed us to compare simulated and measured data. However, ERP paradigms suffer from their limited flexibility in hearing aid fitting as they are restricted to a certain class of stimulation protocols. More recently, we have shown that attention related listening effort correlates can also be extracted from the oscillatory electroencephalographic activity when using a circular analysis of the instantaneous phase organization of Hardy space projected versions of the neural signals. In this talk, we are going (a) to review these approaches, (b) present results that show that the oscillatory method allows for the extraction of listening effort correlates in real life fitting settings, and (c) discuss the potential of time-resolved listening effort profiles. We think that the latter will stimulate new ideas what objective methods can do and what subjective psychometric methods cannot do.

Fitting of hearing aids with different technical parameters to a patient with dead regions

Fitting of hearing aids with different technical parameters to a patient with dead regions The purpose of the study was to determine an optimal hearing aid fitting procedure for a patient with well diagnosed high-frequency ‘dead regions’ in both cochleas. The patient reported non-symmetrical hearing problems of sensorineural origin. For binaural amplification two similar independent hearing aids were used as well as a pair of dependent devices with an ear-to-ear function. Two fitting methods were used: DSLi/o and NAL-NL1, and four different strategies of fitting were tested: the initial fitting based on the DSLi/o or NAL-NL1 method with necessary loudness corrections, the second fitting taking into account all the available functions of hearing instruments, the third fitting (based on the second one) but with significantly reduced amplification well above one octave of frequency inside dead region, and the final fitting with significantly reduced gain slightly below one octave inside dead regions. The results of hearing aids fitting were assessed using an APHAB procedure.

Spectro-Temporal Characteristics of Speech at High Frequencies, and the Potential for Restoration of Audibility to People with Mild-to-Moderate Hearing Loss

It is possible for auditory prostheses to provide amplification for frequencies above 6 kHz. However, most current hearing-aid fitting procedures do not give recommended gains for such high frequencies. This study was intended to provide information that could be useful in quantifying appropriate high-frequency gains, and in establishing the population of hearing-impaired people who might benefit from such amplification. The study had two parts. In the first part, wide-bandwidth recordings of normal conversational speech were obtained from a sample of male and female talkers. The recordings were used to determine the mean spectral shape over a wide frequency range, and to determine the distribution of levels (the speech dynamic range) as a function of center frequency. In the second part, audiometric thresholds were measured for frequencies of 0.125, 0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, and 12.5 kHz for both ears of 31 people selected to have mild or moderate cochlear hearing loss. The hearing loss was never greater than 70 dB for any frequency up to 4 kHz. The mean spectrum level of the speech fell progressively with increasing center frequency above about 0.5 kHz. For speech with an overall level of 65 dB SPL, the mean 1/3-octave level was 49 and 37 dB SPL for center frequencies of 1 and 10 kHz, respectively. The dynamic range of the speech was similar for center frequencies of 1 and 10 kHz. The part of the dynamic range below the root-mean-square level was larger than reported in previous studies. The mean audiometric thresholds at high frequencies (10 and 12.5 kHz) were relatively high (69 and 77 dB HL, respectively), even though the mean thresholds for frequencies below 4 kHz were 41 dB HL or better. To partially restore audibility for a hearing loss of 65 dB at 10 kHz would require an effective insertion gain of about 36 dB at 10 kHz. With this gain, audibility could be (partly) restored for 25 of the 62 ears assessed.

Modelling categorical loudness perception for arbitrary listeners and sounds

While "classical" loudness models predict loudness in sone using the concepts of Stevens' compressive power law, (subdivided) categorical loudness perception after Heller follows the compressive logarithmic Weber‐Fechner law. To bridge the gap between both approaches, this contribution reviews various steps towards a loudness model that predicts categorical loudness (in categorical units, CU) for normal and hearing‐impaired listeners for arbitrary sounds. It uses a (modified) classical loudness model for stationary signals to derive the loudness in sone and a nonlinear transformation from sone to CU. This transformation is approximated by a cubic polynomial equation wich is derived from categorical loudness data of 84 normal‐hearing subjects. The model parameters are further set to predict the standard isophones that are in good agreement with the equal loudness level contours derived from categorical loudness data. Also, the model predicts the loudness functions near threshold both for normal and hearing‐impaired listeners and can be extended to predict duration‐dependent loudness perception. Since categorical loudness can be measured more easily and directly than loudness in sone, the current modelling approach can be experimentally tested and can be used in various applications, such as, e.g. hearing aid processing and fitting procedures.

Comparison of speech intelligibility in quiet and in noise after hearing aid fitting according to a purely prescriptive and a comparative fitting procedure

We compared two different types of hearing-aid fitting procedures in a double-blind randomized clinical study. Hearing aid fittings based on a purely prescriptive procedure (the NAL-RP formula) were compared to a comparative fitting procedure based on optimizing speech intelligibility scores. Main outcome measures were improvement of speech intelligibility scores in quiet and in noise. Data were related to the real-ear insertion responses that were measured after fitting. For analysis purposes subgroups were composed according to degree of hearing loss, characterized by unaided speech intelligibility in quiet, previous experience with hearing aids, unilateral or bilateral fittings and type of hearing aid. We found equal improvement of speech intelligibility in quiet, while fitting according to the prescriptive formula resulted in a somewhat better performance as expressed by the speech-to-noise ratio in comparison to the comparative procedure. Both procedures resulted in comparable real-ear insertion responses.

Comparative studies on hearing aid selection and fitting procedures: a review of the literature

Although a large number of fitting procedures have been developed and are nowadays generally applied in modern hearing aid fitting technology, little is known about their effectiveness in comparison with each other. This paper argues the need for comparative validation studies on hearing aid fitting procedures based on the design of a randomized clinical trial and carried out in a large-scale clinical population. These studies are hard to conduct but can provide detailed information on the various aspects of the rehabilitation with hearing aids. The design of several recently reported comparative studies of hearing aid fitting procedures will be reviewed. This gives rise to a number of comments on aspects like, study design, composition of the study population and definition of outcome measures rather than on the outcome or conclusions of these studies themselves.

Fitting Hearing Aids Using Clinical Measures of Loudness Discomfort Levels: An Evidence-Based Review of Effectiveness

Clinical measurement of the loudness discomfort level (LDL) historically has been part of the hearing aid fitting procedure, and this clinical practice remains popular today. LDL measurements also are recommended in contemporary hearing aid fitting protocols. Yet, surveys show that many hearing aid users are dissatisfied with the loudness of their hearing aids. In this evidence-based review article, we evaluate the effectiveness of clinical LDL measurements. Specifically, we asked the question "Are the clinical measurements of LDL for adult patients predictive of aided acceptance and satisfaction of loudness for high inputs in the real world?" Nearly 200 articles were reviewed; three met the criteria set forth in this review. The evidence supported using unaided LDLs for selecting the maximum real-ear output of hearing aids. No study using aided LDLs or aided loudness verification met the criteria. The level of the evidence for the three articles using unaided LDLs was low; no higher than Level 4. The limited number of studies, the level of evidence, and the statistical power of the studies prevents us from making a strong recommendation concerning the clinical use of LDL measures. Additional research in this area, especially research employing randomized controlled trials would be a useful addition to this body of literature.

A novel signal-processing strategy for hearing-aid design: neurocompensation

A novel approach to hearing-aid signal processing is described, which attempts to re-establish a normal neural representation in the sensorineural impaired auditory system. Most hearing-aid fitting procedures are based on heuristics or some initial qualitative theory. These theories, such as loudness normalization, loudness equalization or maximal intelligibility can give vastly different results for a given individual, and each may provide variable results for different hearing impaired individuals with the same audiogram. Recent research in characterizing sensorineural hearing loss has delineated the importance of hair cell damage in understanding the bulk of sensorineural hearing impairments. A novel methodology based on restoring normal neural representation after the sensorineural impairment is presented here. This approach can be used for designing hearing-aid signal processing algorithms, as well as providing a general, automated means of predicting the relative intelligibility of a given speech sample in normal hearing and hearing impaired subjects.

Hearing aid fitting procedures--state-of-the-art and current issues.

The increasing degree of sophistication in hearing aid technology calls for appropriate fitting strategies, as otherwise hearing aid users cannot receive the full benefit from the most modern technological achievements. This paper describes the state of the art in hearing aid fitting procedures and offers a look into possible future developments. Currently, threshold-based fitting formula compete with loudness- and sound-based fitting procedures. Whereas threshold-based approaches are straightforward and timesaving, they do not consider loudness growth and the sound preferences of the listener. On the other hand, loudness- and sound-based procedures do take these aspects into account, but they are time consuming and it is not yet proven that they provide higher benefit for the end user. This may be due to the fact that either there is actually no extra benefit or more likely that the evaluation tools or study designs have to be improved. Concerns about how to fit more advanced future hearing instruments seem to be inappropriate, as an analysis of possible future signal processing algorithms shows that they probably do not need extra fitting to the individual hearing impairment but rather need optimization according to the acoustical environment.

Insert earphones: Calibration and reference thresholds

Since their introduction in 1984, insert earphones (Etymotic ER-3A and EARtone 3A) have gained widespread popularity for numerous applications in audiology, hearing science, and for different hearing aid fitting procedures. This informational poster describes several procedures that can be used for output calibration using different coupler types specified by ANSI, IEC, and ISO. This will be done by describing step-by-step calibration procedures. Further, ANSI and ISO insert earphone reference threshold levels for pure tones and speech will be presented for different coupler types.

A modified hearing aid fitting procedure using both real ear and 2cc coupler measurement system.

In order to reduce the test time in real ear hearing-aid fitting for children, the validity of applying the average real ear to coupler differences (RECDs) in prefitting procedure using a 2cc coupler measurement system was evaluated by checking whether the majority of people's RECDs might occur within 5 dB of the average RECDs (N = 116) in each test frequency and age group. The percentages of occurrence were around 90% in test subjects' RECDs in saturation sound pressure levels (SSPLs) and around 70% in gain in each important test frequency. Appropriate test frequencies in prefitting are 500, 1000, 1500 and 2000 Hz.

Fitting Hearing Aids to Individual Loudness-Perception Measures

The purpose of this study was to compare the prescribed gain, compression ratios, compression thresholds, and the relative predicted speech intelligibility (Speech Intelligibility Index [SII], American National Standards Institute 3.79, proposed) provided by four strategies proposed for selecting hearing aid parameters for low-threshold compression hearing instruments and by a traditional threshold-based hearing aid fitting procedure. The strategies used were Desired Sensation Level Input/Output (DSLTM[i/o]; Cornelisse, Seewald, & Jamieson, 1994), Visual Input-Output Locator Algorithm (VIOLA; Cox, 1994), FIG6 strategy (Killion, Reference Note 2), Ricketts and Bentler strategy (RAB), and a threshold-based hearing aid fitting procedure (National Acoustics Laboratories-Revised [NAL-R]; Byrne & Dillion, 1986). These new strategies have been suggested as alternatives to threshold-based strategies, which do not provide the varying amounts of target gain, as a function of input level, necessary to fit low-threshold compression hearing aids. The electroacoustic prescriptions and the predicted speech intelligibility were calculated across all five fitting strategies for 20 subjects. The threshold and loudness growth information used for each fitting was reported previously (Ricketts & Bentler, in press). Comparison across prescriptions revealed that the NAL-R strategy (due to the linear gain provided) prescribed the least gain for low-level inputs and the greatest gain for high-level inputs. Gain comparisons across fitting by loudness (FBL) strategies revealed a more shallow frequency response slope for strategies that require individual measures of loudness growth (RAB, VIOLA) in comparison with strategies that assumed average data (FIG6, DSLTM[i/o]). SII results revealed greater predicted speech intelligibility for the FIG6 and the DSLTM[i/o] compared with the NAL-R, RAB, and VIOLA. These differences were most apparent in noise backgrounds and least evident when loudness differences were minimized. It appears that differences in SII scores across the FBL fitting strategies are due, in part, to differences in the loudness of the output signal. It is assumed that differences in high-frequency shaping may also be a factor. These data do not appear to support the use of additional clinical time to obtain individual loudness growth measures. However, due to the fact that SII results are based on average performance, it is difficult to predict whether differences across these fitting strategies would be realized in actual measures of speech intelligibility or sound quality on an individual basis.