Directional Microphone Technology Research Articles

Evaluation of Potential Benefits and Limitations of Noise-Management Technologies for Children with Hearing Aids.

Children with hearing loss frequently experience difficulty understanding speech in the presence of noise. Although remote microphone systems are likely to be the most effective solution to improve speech recognition in noise, the focus of this study centers on the evaluation of hearing aid noise management technologies including directional microphones, adaptive noise reduction (ANR), and frequency-gain shaping. These technologies can improve children's speech recognition, listening comfort, and/or sound quality in noise. However, individual contributions of these technologies as well as the effect of hearing aid microphone mode on localization abilities in children is unknown. The objectives of this study were to (1) compare children's speech recognition and subjective perceptions across five hearing aid noise management technology conditions and (2) compare localization abilities across three hearing aid microphone modes. A single-group, repeated measures design was used to evaluate performance differences and subjective ratings. Fourteen children with mild to moderately severe hearing loss. Children's sentence recognition, listening comfort, sound quality, and localization were assessed in a room with an eight-loudspeaker array. The use of adaptive directional microphone technology improves children's speech recognition in noise when the signal of interest arrives from the front and is spatially separated from the competing noise. In contrast, the use of adaptive directional microphone technology may result in a decrease in speech recognition in noise when the signal of interest arrives from behind. The use of a microphone mode that mimics the natural directivity of the unaided auricle provides a slight improvement in speech recognition in noise compared with omnidirectional use with limited decrement in speech recognition in noise when the signal of interest arrives from behind. The use of ANR and frequency-gain shaping provide no change in children's speech recognition in noise. The use of adaptive directional microphone technology, ANR, and frequency-gain shaping improve children's listening comfort, perceived ability to understand speech in noise, and overall listening experience. Children prefer to use each of these noise management technologies regardless of whether the signal of interest arrives from the front or from behind. The use of adaptive directional microphone technology does not result in a decrease in children's localization abilities when compared with the omnidirectional condition. The best localization performance occurred with use of the microphone mode that mimicked the directivity of the unaided auricle.

Increasing the Effectiveness of Hearing Aid Directional Microphones.

Directionality is the only hearing aid technology — in addition to amplification — proven to help hearing aid users hear better in noise. Hearing aid directionality has been documented to improve speech intelligibility in multiple laboratory studies. In contrast, real-world studies have shown a disconnect between the potential of the technology and what hearing aid users experience in their daily life. This article describes the real-world studies that inspired ReSound to take a different approach to applying directional microphone technology. This approach is based on the idea that hearing aid directionality can leverage natural binaural hearing and inherent listening strategies. The directional strategy includes three listening modes that will be explained. These are the Spatial Cue Preservation mode, the Binaural Listening mode, and the Speech Intelligibility mode. The strategy and the advantages it provides in terms of sound quality, spatial hearing, and improved signal-to-noise ratio with maintained awareness of surroundings are explained.

The Benefit of Remote and On-Ear Directional Microphone Technology Persists in the Presence of Visual Information.

Both the Roger remote microphone and on-ear, adaptive beamforming technologies (e.g., Phonak UltraZoom) have been shown to improve speech understanding in noise for cochlear implant (CI) listeners when tested in audio-only (A-only) test environments. Our aim was to determine if adult and pediatric CI recipients benefited from these technologies in a more common environment-one in which both audio and visual cues were available and when overall performance was high. Ten adult CI listeners (Experiment 1) and seven pediatric CI listeners (Experiment 2) were tested. Adults were tested in quiet and in two levels of noise (level 1 and level 2) in A-only and audio-visual (AV) environments. There were four device conditions: (1) an ear canal-level, omnidirectional microphone (T-mic) in quiet, (2) the T-mic in noise, (3) an adaptive directional mic (UltraZoom) in noise, and (4) a wireless, remote mic (Roger Pen) in noise. Pediatric listeners were tested in quiet and in level 1 noise in A-only and AV environments. The test conditions were: (1) a behind-the-ear level omnidirectional mic (processor mic) in quiet, (2) the processor mic in noise, (3) the T-mic in noise, and (4) the Roger Pen in noise. In each test condition, sentence understanding was assessed (percent correct) and ease of listening ratings were obtained. The sentence understanding data were entered into repeated-measures analyses of variance. For both adult and pediatric listeners in the AV test conditions in level 1 noise, performance with the Roger Pen was significantly higher than with the T-mic. For both populations, performance in level 1 noise with the Roger Pen approached the level of baseline performance in quiet. Ease of listening in noise was rated higher in the Roger Pen conditions than in the T-mic or processor mic conditions in both A-only and AV test conditions. The Roger remote mic and on-ear directional mic technologies benefit both speech understanding and ease of listening in a realistic laboratory test environment and are likely do the same in real-world listening environments.

Effect of Directional Microphone Technology in Hearing Aids on Neural Correlates of Listening and Memory Effort: An Electroencephalographic Study.

The aim of the study was to compare the effect of different spatial noise-processing algorithms in hearing aids on listening effort and memory effort on a subjective, behavioral, and neurophysiological level using electroencephalography (EEG). Two types of directional microphone (DM) technologies for spatial noise processing were chosen: one with a wide directionality (wide DM) and another with a narrower directionality (narrow DM) to accentuate the speech source. Participants with a severe hearing loss were fitted with hearing aids and participated in two EEG experiments. In the first one, participants listened to sentences in cafeteria noise and were asked to rate the experienced listening effort. The second EEG experiment was a listening span task during which participants had to repeat sentence material and then recall the final words of the last four sentences. Subjective listening effort was lower with narrow than wide DM and EEG alpha power was reduced for the narrow DM. The results of the listening span task indicated a reduction in experienced memory effort and better memory performance. During the memory retention phase, EEG alpha level for the narrow relative to the wide DM was reduced. This effect was more pronounced during linguistically difficult sentences. This study extends previous findings, as it reveals a benefit for narrow DM in terms of cognitive performance and memory effort also on a neural level, and when speech intelligibility is almost 100%. Together, this indicates that a narrow and focused DM allows for a more efficient neurocognitive processing than a wide DM.

The Acceptable Noise Level Benefit From Directionality for Listeners With Severe Hearing Loss.

Objectives Directional microphone technology can enhance the speech intelligibility and listening comfort of listeners with hearing impairment. The main aim of this study is to investigate and compare the benefit derived by listeners with severe hearing loss from directional microphone technology with that derived by listeners with moderate hearing loss.Methods The acceptable noise levels (ANLs) of two groups of listeners with moderate or severe hearing impairment (17 subjects in each group) were measured under unaided, omnidirectional-baseline-aided, and directional-aided conditions.Results Although the absolute ANL of the listeners in the severe hearing loss group was significantly higher than that of the listeners in the moderate hearing loss group, their derived benefit was equivalent to that derived by the listeners in the moderate hearing loss group. ANL and hearing loss degree were significantly related. Specifically, the ANL increased with the severity of hearing loss.Conclusion Directional microphone technology can provide the benefits of listening comfort to listeners with severe hearing loss.

The Effects of Directional Processing on Objective and Subjective Listening Effort.

The purposes of this investigation were (a) to evaluate the effects of hearing aid directional processing on subjective and objective listening effort and (b) to investigate the potential relationships between subjective and objective measures of effort. Sixteen adults with mild to severe hearing loss were tested with study hearing aids programmed with 3 settings: omnidirectional, fixed directional, and bilateral beamformer. A dual-task paradigm and subjective ratings were used to assess objective and subjective listening effort, respectively, in 2 signal-to-noise ratios. Testing occurred in rooms with either low or moderate reverberation. Directional processing improved subjective and objective listening effort, although benefit for objective effort was found only in moderate reverberation. Subjective reports of work and tiredness were more highly correlated with word recognition performance than objective listening effort. However, subjective ratings about control were significantly correlated with objective listening effort. Directional microphone technology in hearing aids has the potential to improve listening effort in moderately reverberant environments. In addition, subjective questions that probe a listener's desire to exercise control may be a viable method for eliciting ratings that are significantly related to objective listening effort.

The relationship between the acceptance of noise and acoustic environments in young adults with normal hearing: a pilot study.

The acceptable noise level (ANL) indicates how much background noise a listener is willing to accept while listening to speech. The clinical impact and application of the ANL measure is as a predictor of hearing-aid use. The ANL may also correlate with the percentage of time spent in different listening environments (i.e., quiet, noisy, noisy with speech present, etc). Information retrieved from data logging could confirm this relationship. Data logging, using sound scene analysis, is a method of monitoring the different characteristics of the listening environments that a hearing-aid user experiences during a period. The purpose of this study was to determine if the ANL procedure reflects the proportion of time a person spends in different acoustic environments. This was a descriptive quasi-experimental design to collect pilot data in which participants were asked to maintain their regular, daily activities while wearing a data-logging device. After completing the ANL measurement, 29 normal-hearing listeners were provided a data-logging device and were instructed on its proper use. ANL measures were obtained along with the percentage of time participants spent in listening environments classified as quiet, speech-in-quiet, speech-in-noise, and noise via a data-logging device. An analysis of variance using a general linear model indicated that listeners with low ANL values spent more time in acoustic environments in which background noise was present than did those with high ANL values; the ANL data did not indicate differences in how much time listeners spent in environments of differing intensities. To some degree, the ANL is reflective of the acoustic environments and the amount of noise that the listener is willing to accept; data logging illustrates the acoustic environments in which the listener was present. Clinical implications include, but are not limited to, decisions in patient care regarding the need for additional counseling and/or the use of digital noise reduction and directional microphone technology.

Improving effectiveness of directional microphones with Soft Level Directivity

While today’s hearing instrumen ts have many features, and new features are introduced each year, one feature has withstood the test of time for the past 40 years – directional microphone technology. The application of d irectional technology is one of the few methods of impro ving speech u nderstanding in background noise, a patient benefit which has been supported in evidence-based r eviews (e.g. Bentler, 2005). Most modern directional hearing aids are automatic and adaptive. Automatic, in that based on the signal d etected by the classification system, the directional tec hnology will either be activated or de-activated (omni directional amplification) for individual listening situations. Adaptive, meaning that the directional polar pattern will automatically be altered to maximize speech understan ding for a given speech and noise condition, which now even includes switching to anti-cardioid when speech is from behind the hearing aid user (see Chalupper et al., 2011). When counseling patients regarding the benefits of directional technology, we often mention specific listening situations where benefit would be expected—parties, noisy restaurants, large groups, etc. In general, we talk about listening situations where the speech and noise are rel atively loud, ~70 dB SPL or greater. But there ar e many troublesome listening situations, also with an adverse si gnal-to-noise (SNR) ratio, where the speech and noise si gnals are not as intense, maybe only 60 dB SPL, 50 dB SPL, or even softer. While we have made many advances in d irectional technology ov er the years, this is an area where improvement is still needed, and is the focus of this paper.

The national protocol for paediatric amplification in Australia

This document describes the national protocol for the selection, fitting, verification, and evaluation of amplification for hearing-impaired children in Australia. It also outlines the approach to management of children who have auditory neuropathy spectrum disorder, children who have mild and unilateral hearing loss, and children who require cochlear implantation. Audiological management of all Australian citizens and permanent residents under twenty-one years of age who have a hearing loss is carried out by the national hearing service provider, Australian Hearing. It is funded by the Australian Government's Hearing Services Program to provide fully subsidised hearing aids, frequency modulated (FM) systems and ongoing audiological management. All hearing aids for children are multi-channel devices that offer wide dynamic range compression, directional microphone technology and feedback cancellation as well as access to multiple listening programs, telecoil and audio-input facilities. Hearing aid gain, frequency response and maximum power output are derived according to the NAL-NL1 prescription procedure and verified using real ear measurements. Amplification benefit is evaluated using a range of speech perception tests and functional assessment questionnaires.SumarioEste documento describe el protocolo nacional para la selección, la adaptación, la verificación y la evaluación de la amplificación en niños hipoacúsicos en Australia. También esboza el acercamiento para el tratamiento de niños con el espectro de desórdenes de neuropatía auditiva, niños con hipoacusia moderada y unilateral y niños que requieren implante coclear. El tratamiento audiológico de todos los ciudadanos australianos y residentes permanentes menores de veintiún años de edad con hipoacusia se lleva a cabo por el proveedor nacional de servicios auditivos: Australian Hearing. Es financiado por el Programa del Gobierno Australiano de Servicios Auditivos para otorgar auxiliares auditivos, sistemas de frecuencia modulada (FM) y tratamiento audiológico subsidiados. Todos los auxiliares auditivos para niños son de tipo multicanal que ofrecen un amplio rango de compresión, tecnología de micrófono direccional y de cancelación de la retroalimentación, así como acceso a múltiples programas, telecoil y múltiples propiedades de ingreso de la señal. La ganancia del auxiliar auditivo, la frecuencia de respuesta y la máxima salida derivan de acuerdo a los procedimientos de las prescripciones NAL-NL1 y se verifican utilizando las mediciones de oído real. El beneficio de la amplificación se evalúa utilizando un rango de pruebas de habla y cuestionarios prescripción de la prueba de rango de habla y cuestionarios de desempeño funcional.

The Impact of Listening with Directional Microphone Technology on Self-Perceived Localization Disabilities and Handicaps

The chief complaint of individuals with hearing impairment is difficulty hearing in noise, with directional microphones emerging as the most capable remediation. Our purpose was to determine the impact of directional microphones on localization disability and concurrent handicap. Fifty-seven individuals participated unaided and then in groups of 19, using omni-directional microphones, directional-microphones, or toggle-switch equipped amplification. The outcome measure was a localization disabilities and handicaps questionnaire. Comparisons between the unaided group versus the aided groups, and the directional-microphone groups versus the other two aided groups revealed no significant differences. None of the microphone schemes either increased or decreased self-perceived localization disability or handicap. Objective measures of localization ability are warranted and if significance is noted, clinicians should caution patients when moving in their environment. If no significant objective differences exist, in light of the subjective findings in this investigation concern over decreases in quality of life and safety with directional microphones need not be considered.

Evaluation of a Second-Order Directional Microphone Hearing Aid: II. Self-Report Outcomes

This clinical trial was undertaken to evaluate the subjective benefit obtained from hearing aids employing automatic switching second-order adaptive directional microphone technology, used in conjunction with digital noise reduction, as compared to a fixed directional microphone or omnidirectional microphone response with the same digital noise reduction. Data were collected for 49 participants across two sites. Both new and experienced hearing aid users were fit bilaterally with behind-the-ear hearing aids using the NAL-NL1 (National Acoustics Laboratory-Nonlinear version 1) prescriptive method with manufacturer default settings for various signal processing (e.g., noise reduction, compression parameters, etc.). During ten days of hearing aid use, participants responded to daily journal questions. Subjective ratings for each of the three hearing aid responses (omnidirectional, automatic-adaptive directional, and automatic-fixed directional) were similar. Overall preference for a microphone condition was equally distributed between no preference, omnidirectional, and automatic adaptive and/or fixed directional.

Evaluation of a Second-Order Directional Microphone Hearing Aid: I. Speech Perception Outcomes

This clinical trial was undertaken to evaluate the benefit obtained from hearing aids employing second-order adaptive directional microphone technology, used in conjunction with digital noise reduction. Data were collected for 49 subjects across two sites. New and experienced hearing aid users were fit bilaterally with behind-the-ear hearing aids using the National Acoustics Laboratory-Nonlinear version 1 (NAL-NL1) prescriptive method with manufacturer default settings for various parameters of signal processing (e.g., noise reduction, compression, etc.). Laboratory results indicated that (1) for the stationary noise environment, directional microphones provided better speech perception than omnidirectional microphones, regardless of the number of microphones; and (2) for the moving noise environment, the three-microphone option (whether in adaptive or fixed mode) and the two-microphone option in its adaptive mode resulted in better performance than the two-microphone fixed mode, or the omnidirectional modes.

A candid round-table discussion on modern digital hearing aids and their features

A panel of prominent audiologists who have conducted independent clinical trial research on digital hearing aids share their insights on the real benefits and limitations of such features as multiple channels, directional-microphone technology, and digital noise reduction found in many of today's most advanced products.

Performance of Directional Microphone Hearing Aids in Everyday Life

This study explored the use patterns and benefits of directional microphone technology in real-world situations experienced by patients who had been fitted with switchable omnidirectional/directional hearing aids. Telephone interviews and paper-and-pencil questionnaires were used to assess perceived performance with each microphone type in a variety of listening situations. Patients who used their hearing aids regularly and switched between the two microphone configurations reported using the directional mode, on average, about one-quarter of the time. From brief descriptions, patients could identify listening situations in which each microphone mode should provide superior performance. Further, they reported encountering listening situations in which an omnidirectional microphone should provide better performance more frequently than listening situations in which the directional microphones should be superior. Despite using the omnidirectional mode more often and encountering situations in which an omnidirectional microphone should provide superior performance more frequently, participants reported the same level of satisfaction with each microphone type.

Making sense of directional microphone hearing aids.

We have witnessed a large increase in the availability of directional microphone hearing aids over the past few years. Directional microphone technology is now available in analog, digitally controlled analog, and digital hearing aids, and has been implemented into both behind-the-ear and in-the-ear styles. This Short Course reviews basic design differences across directional microphone hearing aids. A number of different laboratory and clinical evaluation methods used for assessment of both electroacoustic and behavioral directivity are then reviewed. In addition, the potential impact of test conditions such as room reverberation and type and position of competing noise(s), on listener performance when fit with directional hearing aids are considered. Recommendations and suggestions relating to the clinical and laboratory assessment of directional hearing aids are provided.