Elizabeth Convery

The effect of multi-channel wide dynamic range compression, noise reduction, and the directional microphone on horizontal localization performance in hearing aid wearers

This study examined the effect that signal processing strategies used in modern hearing aids, such as multi-channel WDRC, noise reduction, and directional microphones have on interaural difference cues and horizontal localization performance relative to linear, time-invariant amplification. Twelve participants were bilaterally fitted with BTE devices. Horizontal localization testing using a 360° loudspeaker array and broadband pulsed pink noise was performed two weeks, and two months, post-fitting. The effect of noise reduction was measured with a constant noise present at 80° azimuth. Data were analysed independently in the left/right and front/back dimension and showed that of the three signal processing strategies, directional microphones had the most significant effect on horizontal localization performance and over time. Specifically, a cardioid microphone could decrease front/back errors over time, whereas left/right errors increased when different microphones were fitted to left and right ears. Front/back confusions were generally prominent. Objective measurements of interaural differences on KEMAR explained significant shifts in left/right errors. In conclusion, there is scope for improving the sense of localization in hearing aid users.

The trainable hearing aid: what will it do for clients and clinicians?

Instead of trying to adjust hearing aids to the various acoustic environments where the patient will use them, did you ever dream of a hearing aid that will learn by listening which settings the user prefers? Such an instrument may be here sooner than you think.

Preferred overall loudness. II: Listening through hearing aids in field and laboratory tests

In a laboratory study, we found that normal-hearing and hearing-impaired listeners preferred less than normal overall calculated loudness (according to a loudness model of Moore & Glasberg, ). The current study verified those results using a research hearing aid. Fifteen hearing-impaired and eight normal-hearing participants used the hearing aid in the field and adjusted a volume control to give preferred in median loudness. The hearing aid logged the preferred volume control setting and the calculated loudness at that setting. The hearing-impaired participants preferred loudness levels of −14 phon re normal for input levels from 50 to 89 dB SPL. The normal-hearing participants preferred close to normal overall loudness. In subsequent laboratory tests, using the same hearing aid, both hearing-impaired and normal-hearing listeners preferred less than normal overall calculated loudness, and larger reductions for higher input levels. In summary, the hearing-impaired listeners preferred less than normal overall calculated loudness, whereas the results for the normal-hearing listeners were inconclusive. Sumario En un estudio de laboratorio encontramos que normoacúsicos o hipoacúsicos prefieren una intensidad subjetiva global menor que la calculada (de acuerdo con el modelo de intensidad subjetiva de Moore & Glasberg, ). Este estudio verificó esos resultados usando un auxiliar auditivo de investigación. Quince hipoacúsicos y ocho normoacúsicos usaron el auxiliar auditivo en campo libre y ajustaron el control de volumen hasta el nivel de intensidad subjetiva preferido. El auxiliar auditivo conservó el nivel de control de volumen preferido y el nivel de intensidad subjetiva calculado para esa posición. Los hipoacúsicos prefirieron niveles de intensidad subjetiva de −14 phon re normal, para niveles de presentación de 50 a 89 dB SPL. Los normoacúsicos prefirieron niveles de intensidad subjetiva globales cerca de lo normal. En unas pruebas de laboratorio subsecuentes, usando el mismo auxiliar auditivo tanto los hipoacúsicos como los normoacúsicos prefirieron una intensidad subjetiva global menor que la calculada como normal así como amplias reducciones para los niveles de presentación mayores. En resumen, los hipoacúsicos prefieren intensidades subjetivas globales menores que las calculadas como normales, mientras que los resultados para los normoacúsicos no fueron concluyentes.

Client-based adjustments of hearing aid gain: the effect of different control configurations

Objectives: Facilitating the fine-tuning of advanced hearing aids requires information about the acoustic environment. The concept of a “trainable” hearing aid may provide a more direct approach to hearing aid fine-tuning if the aid user is allowed to control the most important fitting parameters in his/her own acoustic environments. Design: In a laboratory study, the concept of self-adjustment of the gain-frequency response was tested by 24 hearing aid users using four different controllers with a limited number of control functions. Research questions focused on the reproducibility of the fine-tuned responses, the efficiency of the control configurations, and the effects of the control configuration on the end results of the fine-tuning process. Results: The subjects were able to provide systematic and reproducible feedback with respect to their preferences in different acoustic conditions presented audiovisually, achieving an average short- term test/retest standard deviation value of 2.8 dB. Two of the control configurations, featuring volume/slope and volume/bass/treble keys, were found to be more time-efficient and reliable, and were also preferred by 86% of the subjects. Although the control configuration did not have a strong influence on the end result, the gain-frequency response from which the subjects started their adjustments was found to have a significant effect on their preferred settings. Conclusions: Client-based adjustments of hearing aid gain provide a reliable method of individual fine-tuning. The results also showed that a biased correction of amplification is reached via self-adjustment within one session, which reduces the effectiveness of fine-tuning in a traditional clinical setting.

A Self-Fitting Hearing Aid: Need and Concept

The need for reliable access to hearing health care services is growing globally, particularly in developing countries and in remotely located, underserved regions in many parts of the developed world. Individuals with hearing loss in these areas are at a significant disadvantage due to the scarcity of local hearing health care professionals and the high cost of hearing aids. Current approaches to making hearing rehabilitation services more readily available to underserved populations include teleaudiology and the provision of amplification devices outside of the traditional provider-client relationship. Both strategies require access to such resources as dedicated equipment and/or specially trained staff. Another possible strategy is a self-fitting hearing aid, a personal amplification device that is equipped with an onboard tone generator to enable user-controlled, automated, in situ audiometry; an onboard prescription to determine the initial hearing aid settings; and a trainable algorithm to enable user-controlled fine-tuning. The device is thus assembled, fitted, and managed by the user without the need for audiological or computer support. This article details the self-fitting concept and its potential application in both developing and developed countries. Potential advantages and disadvantages of such a device are discussed, and considerations for further investigations into the concept are presented. Overall, the concept is considered technologically viable with the main challenges anticipated to be development of clear, simple user instructions and a delivery model that ensures reliable supplies of instant-fit ear tips and batteries.

Preferred overall loudness. I: Sound field presentation in the laboratory

This study questions the basic assumption that prescriptive methods for nonlinear, wide dynamic range compression (WDRC) hearing aids should restore overall loudness to normal. Fifteen normal-hearing listeners and twenty-four hearing-impaired listeners (with mild to moderate hearing loss, twelve with and twelve without hearing aid experience) participated in laboratory tests. The participants first watched and listened to video sequences and rated how loud and how interesting the situations were. For the hearing-impaired participants, gain was applied according to the NAL-NL1 prescription. Despite the fact that the NAL-NL1 prescription led to less than normal overall calculated loudness, according to the loudness model of Moore and Glasberg (), the hearing-impaired participants rated loudness higher than the normal-hearing participants. The participants then adjusted a volume control to preferred overall loudness. Both normal-hearing and hearing-impaired participants preferred less than normal overall calculated loudness. The results from the two groups of hearing-impaired listeners did not differ significantly. Sumario El estudio cuestiona el planteamiento básico de que los métodos de prescripción de auxiliares no-lineales, de compresión amplia del rango dinámico (WDRC) deben restaurar la intensidad subjetiva global a niveles normales. Quince normo-oyentes y veinticuatro hipoacúsicos (con pérdidas auditivas leves o moderadas, 12 con y 12 sin experiencia en el uso de auxiliares auditivos) participaron en las pruebas de laboratorio. Los participantes primero vieron y atendieron las secuencias de video y calificaron qué tan intensas y qué tan interesantes fueron las situaciones planteadas. Para los participantes hipoacúsicos la ganancia se aplicó de acuerdo con las normas de prescripción NAL-NL1. A pesar del hecho de que esa norma NAL-NL1 permite llegar a una intensidad subjetiva global menor de la normal, de acuerdo con el modelo de intensidad subjetiva de Moore y Glasberg (), los participantes hipoacúsicos calificaron la intensidad subjetiva como mayor que los participantes normoacúsicos. Los participantes ajustaron entonces el control de volumen a los niveles preferidos de intensidad subjetiva. Tanto los normoacúsicos como los participantes hipoacúsicos prefirieron una intensidad subjetiva global menor de la calculada como normal. Los resultados de los dos grupos de hipoacúsicos, no difirieron significativamente.

Management of Hearing Aid Assembly by Urban-Dwelling Hearing-Impaired Adults in a Developed Country Implications for a Self-Fitting Hearing Aid

A self-fitting hearing aid, designed to be assembled and programmed without audiological or computer support, could bring amplification to millions of people in developing countries, who remain unaided due to the lack of a local, professional, audiological infrastructure. The ability to assemble and insert a hearing aid is fundamental to the successful use of a self-fitting device. In this study, the management of such tasks was investigated. Eighty older, urban-dwelling, hearing-impaired adults in a developed country were asked to follow a set of written, illustrated instructions to assemble two slim-fit behind-the-ear hearing aids. Participants were allowed to access assistance with the task from an accompanying partner. A range of personal and audiometric variables was measured through the use of structured questionnaires and standardized tests of health literacy, cognitive function, and manual dexterity. The results showed that 99% of participants were able to complete the hearing aid assembly task, either on their own or with assistance. Health literacy, or the ability to read and understand health-related text, and gender most strongly influenced participants’ ability to complete the assembly task independently and accurately. Higher levels of health literacy were associated with an increased likelihood of independent and successful task completion. Male participants were more likely to complete the task on their own, while female participants were more likely to assemble the device without errors. The results of this study will inform future work regarding development of educational material for the self-fitting hearing aid as well as candidacy for such a device.

The effect of the base line response on self-adjustments of hearing aid gain

Self-adjustments of variable hearing aid parameters are essential for trainable hearing aids to provide customized amplification for different listening environments. Prompted by a finding of Dreschler et al. [Ear Hear. 29, 214-227 (2008)], this study investigates the effect of the base line (starting) response on self-adjustments of gain in different frequency bands. In a laboratory test, 24 hearing-impaired listeners adjusted the bass, treble, and overall gain to reach their preferred responses from two different base line responses for 12 different listening situations. The adjustments were repeated five times using the preferred response after each adjustment as base line response for the next adjustment. Half of the listeners further compared three different response shapes, within the range of preferred responses, pairwise ten times for preferential and perceptual discrimination. The results revealed that base line response biases were more pronounced at low frequencies and for listeners with a flat hearing loss configuration. While 83% of listeners reliably discriminated between the average selected biased responses, only 25% demonstrated reliable preferences for one response over the other. Listeners who showed preferential discrimination ability were those who were less biased by the base line response. The clinical implication is that self-adjustments should begin from an appropriately prescribed starting response.

Self-Fitting Hearing Aids: Status Quo and Future Predictions.

A self-contained, self-fitting hearing aid (SFHA) is a device that enables the user to perform both threshold measurements leading to a prescribed hearing aid setting and fine-tuning, without the need for audiological support or access to other equipment. The SFHA has been proposed as a potential solution to address unmet hearing health care in developing countries and remote locations in the developed world and is considered a means to lower cost and increase uptake of hearing aids in developed countries. This article reviews the status of the SFHA and the evidence for its feasibility and challenges and predicts where it is heading. Devices that can be considered partly or fully self-fitting without audiological support were identified in the direct-to-consumer market. None of these devices are considered self-contained as they require access to other hardware such as a proprietary interface, computer, smartphone, or tablet for manipulation. While there is evidence that self-administered fitting processes can provide valid and reliable results, their success relies on user-friendly device designs and interfaces and easy-to-interpret instructions. Until these issues have been sufficiently addressed, optional assistance with the self-fitting process and on-going use of SFHAs is recommended. Affordability and a sustainable delivery system remain additional challenges for the SFHA in developing countries. Future predictions include a growth in self-fitting products, with most future SFHAs consisting of earpieces that connect wirelessly with a smartphone and providers offering assistance through a telehealth infrastructure, and the integration of SFHAs into the traditional hearing health-care model.

Evaluation of the self-fitting process with a commercially available hearing aid

Background: Hearing aids and personal sound amplification products that are designed to be self‐fitted by the user at home are becoming increasingly available in the online marketplace. While these devices are often marketed as a low‐cost alternative to traditional hearing health‐care, little is known about peoples ability to successfully use and manage them. Previous research into the individual components of a simulated self‐fitting procedure has been undertaken, but no study has evaluated performance of the procedure as a whole using a commercial product. Purpose: To evaluate the ability of a group of adults with a hearing loss to set up a pair of commercially available self‐fitting hearing aids for their own use and to investigate factors associated with a successful outcome. Research Design: An interventional study that used regression analysis to identify potential contributors to the outcome. Study Sample: Forty adults with mild to moderately severe hearing loss participated in the study: 20 current hearing aid users (the “experienced” group) and 20 with no previous amplification experience (the “new” group). Twenty‐four participants attended with partners, who were present to offer assistance with the study task as needed. Data Collection and Analysis: Participants followed a set of written, illustrated instructions to perform a multistep self‐fitting procedure with a commercially available self‐fitting hearing aid, with optional assistance from a lay partner. Standardized measures of cognitive function, health literacy, locus of control, hearing aid self‐efficacy, and manual dexterity were collected. Statistical analysis was performed to examine the proportion of participants in each group who successfully performed the self‐fitting procedure, factors that predicted successful completion of the task, and the contributions of partners to the outcome. Results: Fifty‐five percent of participants were able to successfully perform the self‐fitting procedure. Although the same success rate was observed for both experienced and new participants, the majority of the errors relating to the hearing test and the fine‐tuning tasks were made by the experienced participants, while all of the errors associated with physically customizing the hearing aids and most of the insertion errors were made by the new participants. Although the majority of partners assisted in the self‐fitting task, their contributions did not significantly influence the outcome. Further, no characteristic or combination of characteristics reliably predicted which participants would be successful at the self‐fitting task. Conclusions: Although the majority of participants were able to complete the self‐fitting task without error, the provision of knowledgeable support by trained personnel, rather than a fellow layperson, would most certainly increase the proportion of users who are able to achieve success. Refinements to the instructions and the physical design of the hearing aid may also serve to improve the success rate. Further evaluation of the range of self‐fitting hearing aids that are now on the market should be undertaken.