Amyn M. Amlani

Methods and Applications of the Audibility Index in Hearing Aid Selection and Fitting

During the first half of the 20th century, communications engineers at Bell Telephone Laboratories developed the articulation model for predicting speech intelligibility transmitted through different telecommunication devices under varying electroacoustic conditions. The profession of audiology adopted this model and its quantitative aspects, known as the Articulation Index and Speech Intelligibility Index, and applied these indices to the prediction of unaided and aided speech intelligibility in hearing-impaired listeners. Over time, the calculation methods of these indices-referred to collectively in this paper as the Audibility Index-have been continually refined and simplified for clinical use. This article provides (1) an overview of the basic principles and the calculation methods of the Audibility Index, the Speech Transmission Index and related indices, as well as the Speech Recognition Sensitivity Model, (2) a review of the literature on using the Audibility Index to predict speech intelligibility of hearing-impaired listeners, (3) a review of the literature on the applicability of the Audibility Index to the selection and fitting of hearing aids, and (4) a discussion of future scientific needs and clinical applications of the Audibility Index.

A meta-analysis to compare speech recognition in noise with bilateral cochlear implants and bimodal stimulation

Abstract Objective: This investigation quantified the relative benefits of binaural CI arrangements (i.e., bilateral, bimodal) for three binaural phenomena (i.e., binaural squelch, binaural summation, head-shadow effect) and sensitivity of two speech-recognition test paradigms (i.e., adaptive and fixed). Design: A repeated-measures meta-analytical approach was used to compare effect sizes between binaural CI arrangements for each of the three binaural-listening phenomena and between the two test paradigms. Study sample: A total of 95 effect sizes were calculated and analyzed from 42 peer-reviewed studies published between January 2000 and April 2011. Results: Findings revealed significant effect sizes for both CI arrangements for the binaural phenomena of summation and head-shadow effect. A significant effect size for binaural squelch was determined only for bilateral CI users. Further, the two paradigms resulted in similar effect sizes for bilateral and bimodal users, with the exception of binaural squelch. Here, significant effect sizes were significant only in the fixed-testing paradigm. Conclusions: The average user of binaural CI arrangements realizes the binaural phenomena of summation and the head-shadow effect, but only the bilateral CI arrangement is afforded the advantage of binaural squelch. Statistically, listeners fit with bilateral CIs have a slight advantage in binaural performance over those using bimodal stimulation. Sumario Objetivo: Esta investigación cuantifica los beneficios relativos de las adaptaciones binaurales de IC (p.e., bilaterales, bimodales) en cuanto a tres fenómenos binaurales (p.e., chapoteo binaural, sumación binaural, efecto de sombra de la cabeza) y la sensibilidad de dos paradigmas de prueba para el reconocimiento del lenguaje. Diseño: Se utilizó un enfoque meta-analítico de medidas repetidas para comparar el grado del efecto en las adaptaciones binaurales de CI para cada uno de los tres fenómenos de audición binaural y entre los dos paradigmas de prueba. Muestra Del Estudio: Se calculó y se analizó un total de 95 efectos en 42 estudios con revisión editorial, publicados entre enero del 2000 y abril del 2011. Resultados: Los hallazgos revelaron grados significativos de efecto para ambas adaptaciones de CI, tanto para el fenómeno de sumación como para el de efectos sombra de la cabeza. Se determinó un grado significativo de efecto para el chapoteo binaural sólo para los usuarios de CI bilaterales. Más aún, los dos paradigmas rindieron resultados de grado similar para usuarios bilaterales y bimodales, con la excepción del chapoteo binaural. Aquí, los grados de efecto fueron significativos solamente para el paradigma de prueba fija. Conclusiones: El usuario promedio con adaptación binaurales de CI se da cuenta del fenómeno binaural de sumación y el efecto de sombra de la cabeza, pero solo al arreglo de CI bilateral le da la ventaja del chapoteo binaural. Estadísticamente, los sujetos adaptados con CI bilaterales tienen una ligera ventaja en el desempeño binaural sobre aquellos que utilizan estimulación bimodal.

Speech-clarity judgments of hearing-aid-processed speech in noise: Differing polar patterns and acoustic environments

This investigation assessed the extent to which listeners’ preferences for hearing aid microphone polar patterns vary across listening environments, and whether normal-hearing and inexperienced and experienced hearing-impaired listeners differ in such preferences. Paired-comparison judgments of speech clarity (i.e. subjective speech intelligibility) were made monaurally for recordings of speech in noise processed by a commercially available hearing aid programmed with an omnidirectional and two directional polar patterns (cardioid and hypercardioid). Testing environments included a sound-treated room, a living room, and a classroom. Polar-pattern preferences were highly reliable and agreed closely across all three groups of listeners. All groups preferred listening in the sound-treated room over listening in the living room, and preferred listening in the living room over listening in the classroom. Each group preferred the directional patterns to the omnidirectional pattern in all room conditions. We observed no differences in preference judgments between the two directional patterns or between hearing-impaired listeners’ extent of amplification experience. Overall, findings indicate that listeners perceived qualitative benefits from microphones having directional polar patterns.

Application of Paired-Comparison Methods to Hearing Aids

The method of paired comparisons was introduced into the hearing aid literature nearly 50 years ago. Over time, studies have found paired comparisons to be sensitive, valid, and reliable in determining either the perceptual difference or relative ranking among hearing aids and electroacoustic characteristics. With the increasing number of adjustable electroacoustic parameters in today’s digital hearing aids—and the lack of procedural guidelines necessary to fit many of them—the method of paired comparisons provides the clinician with the ability to compare different devices, electroacoustic characteristics, memory settings, or combinations of these variables under the listener’s everyday listening conditions. Furthermore, this procedure provides the clinician with the ability to individualize the prescriptive approach—which is predicated mainly on hearing threshold data and listening in quiet—so that a combination of parameters can be set to optimize the user’s listening needs in a given environment. In this article, the authors present an overview of the theoretical principle supporting this procedure, the various paired-comparison strategies and associated approaches, the advantages of this method, and recommended procedures for implementing the method of paired comparisons in the fitting of today’s sophisticated hearing aids.

Cost as a Barrier for Hearing Aid Adoption

Grundfast and Liu1 recently provided otolaryngologists with an overview of the hearing aid market. While their viewpoint addressed valid points, some points did not accurately reflect the hearing aid market. In this Viewpoint, we hope to provide otolaryngologists with a more accurate representation of hearing aids as part of audiologic service delivery. Grundfast and Liu1 correctly state that the hearing aid adoption rate is approximately 33%. The authors attribute this “poor” adoption rate primarily to cost, which can exceed

An Acoustical Analysis of the Frequency-Attenuation Response of Musician Earplugs

2000 per unit. We believe that cost is not the primary barrier to adoption and provide the reader with data to support this belief. First, data reveal that the number of hearing aids dispensed in the United States from 2007 to 2016 has steadily increased.2 Second, the Figure, adapted from MarkeTrak 9, a hearing-aid industry marketing survey, illustrates global demand for hearing aids.3 In the Figure, countries with the highest adoption rate are Norway (42.5%), the United Kingdom (41.1%), and Switzerland (38.8%).3 The highest adoption rate in these countries is not surprising because hearing aids are fully (in Norway and Switzerland) or primarily (ie, in the United Kingdom) government subsidized. Looking at Norway, 42.5% of citizens needing hearing aids take advantage of the subsidy by adopting this technology. However, these data also reveal that 57.5% are unwilling to adopt hearing aids despite the fact that no cost is expected from the patient. In the unlikely event the United States subsidized hearing aids, market penetration is estimated to increase by no more than 10%, or that the United States would have an adoption rate similar to that of Norway.4 Finally, a recent study5 reported on 651 veterans screened to have hearing loss. Of those, only 28% complied with the recommendation to seek hearing aids. Furthermore, only 42% of the 28% actually adopted hearing aids, despite the fact that hearing aids are provided at no cost. Likewise, Australian researchers revealed that 39% of adults 50 years or older with hearing loss did not seek assistance for hearing loss6 and 58% failed to adopt hearing aids.7 Hearing health care in these latter examples is provided at minimal or no cost, yet noncompliance and nonintervention remains high. Simply stated, price—private and subsidized—is not the primary requirement to increase clinician compliance and adoption of hearing aids. This is not to suggest that price is not a consideration during the purchasing process, it is just not a primary factor. Other factors impeding hearing aid adoption include heightened social stigma, denial of hearing loss, and reduced self-efficacy.8 Grundfast and Liu1 provided recent policy recommendations by the President’s Council of Advisors on Science and Technology (PCAST) and the National Academies of Sciences, Engineering, and Medicine (NASEM). Two recommendations—personal sound amplification products (PSAPs) and increased access—deserve a brief comment. First, the authors1 note the US Food and Drug Administration (FDA) classifies PSAPs as augmentative amplifying products for listeners exhibiting normal hearing, whereas hearing aids are classified as an amplifying product for listeners exhibiting impaired hearing. Recently, PCAST recommended (and NASEM concurred) that PSAP manufacturers be permitted to advertise products to listeners with impaired hearing. While we advocate PSAPs as entry-level devices, emerging research suggests that some consumer-based devices can optimally reduce (1) the effect of reduced audibility caused by hearing loss, (2) cognitive decline because hearing sensitization is restored, and (3) social isolation. As such, it is essential that PSAPs meet a minimum standard for sound quality, functionality, and benefit. Grundfast and Liu1 do not mention that hearing aid manufacturers must be registered with the FDA and hearing aids must be appropriately labeled (ie, model, serial number) and provide a User Instructional Brochure.9 In addition, hearing aids must meet strict specifications (ie, tolerances) based on American National Standards Institute protocol S.33-2009. That is, minimal differences are present between the same model produced by a hearing aid manufacturer. When hearing aids arrive, the audiologist measures its performance using a hearing aid analyzer. On the one hand, if the hearing aids do not match the hearing aid tolerances, they are returned for replacement. On the other hand, PSAPs are exempt from FDA requirements. That is, tolerances for PSAPs are absent. In addition, hearing aids undergo strenuous in-house and third-party testing related to electroacoustic and behavioral performance to ensure consumer protection against a faulty product. Second, when PSAPs are purchased, no guaranteed audiologic service is included; it is simply “out of the box” and “into the ear.” With hearing aids, audiological follow-up is necessary to ensure the device provides maximum performance to the patient. Examples include (1) measuring the hearing aids in an analyzer to verify adherence to manufacturer specification, (2) programming by using real ear measures (REM) to a prescriptive target assuring maximum speech understanding, (3) providing a 4to 6-week trial to determine if the patient wants to retain the hearing aids, (4) scheduling appointments during the trial period to fine-tune the hearing aids, and (5) scheduling service appointments (repairs, reprogramming, counseling) for maintenance and performance. All these services, and others, represent a considerable difference between the cost of the hearing aids dispensed via an audiologist vs purchasing a PSAP, where no such follow-up care exists. Thus, if cost were the only factor, audiologists could order several hearing aids at a cost equal or less than VIEWPOINT

Application of the Consumer Decision-Making Model to Hearing Aid Adoption in First-Time Users.

Abstract Musician earplugs (MEP) are intended to reduce the risk for noise induced hearing loss among musician populations while providing flat attenuation characteristics. However, survey data suggest that low use rates among musicians are associated with negative listening experiences due to perceived alterations in the spectral characteristics of music. These shortcomings warrant the assessment of how a MEP processes the full frequency and complex spectral nuances of musical sounds. The goal of this study was to assess the influence of musician earplugs on musical stimuli using an acoustic test fixture in order to characterize objectively the influence of customand non-custom-fit MEPs on both the attenuation levels and the spectral characteristics of music in and over a wide range of intensity levels in a simulated human ear canal. Our objective measurements inside ear of KEMAR confirm that the spectral characteristics of music are altered by MEPs, regardless of whether the earplug was a non-custom or custom earplug. The findings suggest that the claims used to market MEPs to musicians and music schools are misleading and that the discrepancies for claiming attenuation characteristics in response to musical stimuli are related, in part, to the use of the REAT testing procedure. New testing protocols are recommended.

An Acoustical Assessment of the Music Memory in Commercially AvailableHearing Aids

Since 1980, hearing aid adoption rates have remained essentially the same, increasing at a rate equal to the organic growth of the population. Researchers have used theoretical models from psychology and sociology to determine those factors or constructs that lead to the adoption of hearing aids by first-time impaired listeners entering the market. In this article, a theoretical model, the Consumer Decision-Making Model (CDM), premised on the neobehavioral approach that considers an individuals psychological and cognitive emphasis toward a product or service, is described. Three theoretical models (i.e., transtheoretical, social model of disability, Health Belief Model), and their relevant findings to the hearing aid market, are initially described. The CDM is then presented, along with supporting evidence of the models various factors from the hearing aid literature. Future applications of the CDM to hearing health care also are discussed.

Efficacy of directional microphone hearing aids: a meta-analytic perspective.

Hearing aids amplify speech-input signals using nonlinear amplification (i.e., wide dynamic range compression). When WDRC is used to process a music-input signal, listener’s report a negative aided listening experience. To circumvent this negative experience, hearing aids allow for music-input stimuli to be processed using a modified frequency-gain response, known as a memory or program. The music memory, in general, processes the input signal using a linear-like frequency-gain response, elevated output, or both. Increasing gain and output, we conjecture, has the potential to place the wearer at-risk (i.e., ≥85 Leq dBA) for Hearing-aid-induced hearing loss (HAIHL). We assessed the potential of this risk in two experiments. In Experiment I, 2-cc coupler gain was determined in three commercially available receiver-in-the ear/receiver-in-the-canal (RITE/RIC) hearing aids. Coupler gain responses were determined for a composite signal presented at 65 and 100 dB SPL for the WDRC memory and music memory, and for different degrees of occlusion. Results from this experiment were reported qualitatively. In Experiment II, the same three devices were fit on an acoustical manikin. Recordings of 10 musical passages were obtained for the same two memories, adjusted for the degree of occlusion at three presentation levels (i.e., 85-, 94-, and 103-dB SPL). Analyses of the recordings revealed that two devices programed in the music mode exceeded the at-risk threshold at presentation levels of 94- and 103-dB SPL. In addition, the same two devices programmed in WDRC exceeded the at-risk threshold at a presentation level of 103-dB SPL. Implications and future directions are discussed.