How directional microphones affect speech recognition,listening effort and localisation for listeners with moderate-to-severe hearing loss

Objective: The purpose of this study was to evaluate the effects of directional microphone use on laboratory measures of sentence recognition, listening effort and localisation. An additional purpose of this study was to evaluate the effects of asymmetric directional microphone use on the same laboratory measures. Design: Three hearing aid conditions were evaluated: (1) bilateral omnidirectional microphones, (2) bilateral directional microphones and (3) asymmetric microphones (directional microphone for only one hearing aid). Sentence recognition performance was evaluated using a connected speech test. Listening effort was evaluated using a dual-task paradigm with a response time-based secondary task requiring word categorisation. Localisation was examined using a complex task requiring localisation and recall of speech originating from one of four loudspeakers in the horizontal plane (?60°, ?45°,?+45°,?+60°). Study sample: Eighteen adults (M?=?61.8 years) with symmetrical, moderate-to-severe hearing loss participated. Results: Performance on each task was analysed separately using a repeated measures analysis of variance. Results revealed directional benefits for sentence recognition and listening effort, but microphone setting did not affect localisation. Performance was equivalent with symmetric and asymmetric directional configurations. Conclusions: Bilateral and asymmetric directional microphone configurations equally improved sentence recognition and listening effort; neither affected localisation or recall.     

A directional remote-microphone for bimodal cochlear implant recipients

Abstract

To evaluate whether speech recognition in noise differs according to whether a wireless remote microphone is connected to just the cochlear implant (CI) or to both the CI and to the hearing aid (HA) in bimodal CI users. The second aim was to evaluate the additional benefit of the directional microphone mode compared with the omnidirectional microphone mode of the wireless microphone. This prospective study measured Speech Recognition Thresholds (SRT) in babble noise in a ‘within-subjects repeated measures design’ for different listening conditions. Eighteen postlingually deafened adult bimodal CI users. No difference in speech recognition in noise in the bimodal listening condition was found between the wireless microphone connected to the CI only and to both the CI and the HA. An improvement of 4.1?dB was found for switching from the omnidirectional microphone mode to the directional mode in the CI only condition. The use of a wireless microphone improved speech recognition in noise for bimodal CI users. The use of the directional microphone mode led to a substantial additional improvement of speech perception in noise for situations with one target signal.     

正常听力受试者佩戴不同组合全向性与方向性麦克风的效果比较

目的 比较噪声环境下全向性麦克风与自适应方向性麦克风的不同组合佩戴方式对听力正常成年人言语识别率的影响,从而选择最佳的组合佩戴方式.方法 选择20例(40耳)听力正常青年人(男、女各10例)分别按照双耳全向性麦克风模式(组合1),双耳自适应方向性麦克风模式(组合2),一耳全向性麦克风、一耳自适应麦克风模式(组合3)3种方式,在信噪比变化的漫射声场中进行言语识别率测试,从而进行助听效果的评估.结果 组合1、2、3三种方式测出的L50值(50%言语识别率的信噪比)分别为-3.55±2.37 dB,-7.15±2.18 dB,-5.40±2.35 dB,三者之间两两比较差异均有显著统计学意义(P<0.05).结论 噪声环境下无论双耳佩戴自适应方向性麦克风模式还是一耳佩戴自适应方向性麦克风、另一耳佩戴全向性麦克风,其言语识别能力均高于双耳佩戴全向性麦克风模式,且双耳佩戴自适应方向性麦克风模式的言语识别率高于一耳自适应麦克风、一耳全向性麦克风模式.     

The effects of asymmetric directional microphone fittings on acceptance of background noise

Abstract

Objective: The effects of asymmetric directional microphone fittings (i.e., an omnidirectional microphone on one ear and a directional microphone on the other) on speech understanding in noise and acceptance of background noise were investigated in 15 full-time hearing aid users. Design: Subjects were fitted binaurally with four directional microphone conditions (i.e., binaural omnidirectional, right asymmetric directional, left asymmetric directional and binaural directional microphones) using Siemens Intuis Directional behind-the-ear hearing aids. Speech understanding in noise was assessed using the Hearing in Noise Test, and acceptance of background noise was assessed using the Acceptable Noise Level procedure. Speech was presented from 0° while noise was presented from 180° azimuth. Results/Conclusions: The results revealed that speech understanding in noise improved when using asymmetric directional microphones compared to binaural omnidirectional microphone fittings and was not significantly hindered compared to binaural directional microphone fittings. The results also revealed that listeners accepted more background noise when fitted with asymmetric directional microphones as compared to binaural omnidirectional microphones. Lastly, the results revealed that the acceptance of noise was further increased for the binaural directional microphones when compared to the asymmetric directional microphones, maximizing listeners' willingness to accept background noise in the presence of noise. Clinical implications will be discussed.

Sumario

Objetivo: Se investigaron los efectos de la adaptación de micrófonos asimétricos direccionales (i.e., un micrófono omnidireccional en un oído y uno direccional en el otro) sobre la comprensión del lenguaje en ruido y la aceptación del ruido de fondo en 15 usuarios de auxiliares auditivos de tiempo completo. Diseño: A los sujetos se les adaptaron binauralmente micrófonos direccionales en cuatro condiciones: (i.e., binaural omnidireccional, direccional derecho asimétrico, izquierdo direccional asimétrico y binaural direccional) utilizando los auxiliares auditivos tipo retroauricular Siemens Intuis Direccional. La comprensión del lenguaje en ruido fue evaluada utilizando la Prueba de Audición en Ruido y la aceptación del ruido de fondo fue evaluada utilizando el procedimiento de Nivel de Ruido Aceptable. El lenguaje se presentó a 0° mientras que el ruido se presentó a un azimut de 180°. Resultados/Conclusiones: Los resultados revelan que la comprensión del lenguaje en ruido mejoró cuando se utilizan micrófonos direccionales asimétricamente, en comparación con los micrófonos omnidireccionales en forma binaural y no se dificultó significativamente al compararse con los micrófonos direccionales en forma binaural. Estos resultados también revelaron que los oyentes aceptan mayor ruido de fondo cuando se les adaptan micrófonos asimétricos direccionales en comparación con los micrófonos omnidireccionales en forma binaural. Por ultimo, los resultados revelan que la aceptación de ruido aumentó con los micrófonos direccionales bianurales cuando se compararon con los micrófonos direccionales asimétricos, maximizando la disposición de los oyentes para aceptar el ruido de fondo en presencia de ruido. Las implicaciones clínicas serán discutidas.     

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.     

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.     

Evaluation of the benefit for cochlear implantees of two assistive directional microphone systems in an artificial diffuse noise situation

OBJECTIVE: People with cochlear implants have severe problems with speech understanding in noisy surroundings. This study evaluates and quantifies the effect of two assistive directional microphone systems compared to the standard headpiece microphone on speech perception in quiet surroundings and in background noise, in a laboratory setting developed to reflect a situation whereby the listener is disturbed by a noise with a mainly diffuse character due to many sources in a reverberant room. DESIGN: Thirteen postlingually deafened patients, implanted in the Leiden University Medical Centre with the Clarion CII device, participated in the study. An experimental set-up with 8 uncorrelated steady-state noise sources was used to test speech perception on monosyllabic words. Each subject was tested with a standard headpiece microphone, and the two assistive directional microphones, TX3 Handymic by Phonak and the Linkit array microphone by Etymotic Research. Testing was done in quiet at a level of 65 dB SPL and with decreasing signal-to-noise ratios (SNR) down to -15 dB. RESULTS: Using the assistive directional microphones, speech recognition in background noise improved substantially and was not affected in quiet. At an SNR of 0 dB, the average CVC scores improved from 45% for the headpiece microphone to 67% and 62% for the TX3 Handymic and the Linkit respectively. Compared to the headpiece, the Speech Reception Threshold (SRT) improved by 8.2 dB SNR and 5.9 dB SNR for the TX3 Handymic and the Linkit respectively. The gain in SRT for TX3 Handymic and Linkit was neither correlated to the SRT score with headpiece nor the duration of CI-use. CONCLUSION: The speech recognition test in background noise showed a clear benefit from the assistive directional microphones for cochlear implantees compared to the standard microphone. In a noisy environment, the significant benefit from these assistive device microphones may allow understanding of speech with greater ease.     

Relationship between laboratory measures of directional advantage and everyday success with directional microphone hearing aids

The improvement in speech recognition in noise obtained with directional microphones compared to omnidirectional microphones is referred to as the directional advantage. Laboratory studies have revealed substantial differences in the magnitude of the directional advantage across hearing-impaired listeners. This investigation examined whether persons who were successful users of directional microphone hearing aids in everyday living tended to obtain a larger directional advantage in the test booth than persons who were unsuccessful users. Results revealed that the mean directional advantage did not differ significantly between patients who used the directional mode regularly and those who reported little or no benefit from directional microphones in daily living and, therefore, tended to leave their hearing aids set in the default omnidirectional mode. Success with directional microphone hearing aids in everyday living, therefore, cannot be reliably predicted by the magnitude of the directional advantage obtained in the clinic.     

Speech intelligibility in noisy environments with one- and two-microphone hearing aids

In this study speech intelligibility in background noise was evaluated with 10 binaural hearing-aid users for hearing aids with one omnidirectional microphone and a hearing aid with a two-microphone configuration (enabling an omnidirectional as well as a directional mode). Signal-to-noise ratio (SNR) measurements were carried out for three different types of background noise (speech-weighted noise, traffic noise and restaurant noise) and two kinds of speech material (bisyllabic word lists and sentences). The average SNR improvement of the directional microphone configuration relative to the omnidirectional one was 3.4 dB for noise presented from 90 degrees azimuth. This improvement was independent of the specific type of noise and speech material, indicating that one speech-in-noise condition may yield enough relevant information in the evaluation of directional microphones and speech understanding in noise.     

Aplicación de la tecnología de enrutamiento inalámbrico contralateral de la señal (CROS) en usuarios de implante coclear unilateral

IntroductionSingle cochlear implantation usually provides substantial speech intelligibility benefits but bilaterally deaf, unilaterally implanted subjects will continue to experience limitations due to the head shadow effect, like single-sided deaf individuals. In the treatment of individuals with single-sided deafness one option is contralateral routing of signal (CROS) devices, which constitute a non-surgical intervention of the second ear in unilaterally implanted individuals.MethodTwelve experienced adult cochlear implant users with Naída Q70 processor and the CROS device used in combination participated in the study. For the study 3 conditions were provided: cochlear implant only, omnidirectional microphone mode (CROS deactivated); cochlear implant plus CROS activated, omnidirectional microphone mode and cochlear implant plus CROS activated, UltraZoom mode. Speech reception thresholds were determined in quiet and noise. Subjective feedback regarding the practical usability of the CROS device and the perceived benefit were collected.ResultsThere was a 27.6% improvement in speech understanding in quiet and 32.5% improvement in noise when CROS device was activated. Using advanced directional microphones, a statistically significant benefit of 35% was obtained. The responses to the questionnaires revealed that the subjects perceived benefit in their everyday lives when using the CROS device with their cochlear implants.ConclusionThe investigated CROS device used by unilateral CI recipients in cases where bilateral implantation is not an option provides both subjective and objective speech recognition benefit when the signal is directed to the CROS device. Unfavourable conditions where speech is presented from the cochlear implant side and noise from the CROS side or diffusely were not included in this evaluation since the CROS device adds additional noise and performance is expected to decrease as has previously been shown.     

Better speech perception in noise with an assistive multimicrophone array for hearing AIDS

OBJECTIVE: To evaluate the improvement in speech intelligibility in noise obtained with an assistive real-time fixed endfire array of bidirectional microphones in comparison with an omnidirectional hearing aid microphone in a realistic environment. DESIGN: The microphone array was evaluated physically in anechoic and reverberant conditions. Perceptual tests of speech intelligibility in noise were carried out in a reverberant room, with two types of noise and six different noise scenarios with single and multiple noise sources. Ten normal-hearing subjects and 10 hearing aid users participated. The speech reception threshold for sentences was measured in each test setting for the omnidirectional microphone of the hearing aid and for the hearing aid in combination with the array with one and three active microphones. In addition, the extra improvement of five active array microphones, relative to three, was determined in another group of 10 normal-hearing listeners. RESULTS: Improvements in speech intelligibility in noise obtained with the array relative to an omnidirectional microphone depend on noise scenario and subject group. Improvements up to 12 dB for normal-hearing and 9 dB for hearing-impaired listeners were obtained with three active array microphones relative to an omnidirectional microphone for one noise source at 90 degrees . For three uncorrelated noise sources at 90 degrees, 180 degrees, and 270 degrees, improvements of approximately 9 dB and 6 dB were obtained for normal-hearing and hearing-impaired listeners, respectively. Even with a single noise source at 45 degrees, benefits of 4 dB were achieved in both subject groups. Five active microphones in the array can provide an additional improvement at 45 degrees of approximately 1 dB, relative to the three-microphone configuration for normal-hearing listeners. CONCLUSIONS: These improvements in signal-to-noise ratio can be of great benefit for hearing aid users, who have difficulties with speech understanding in noisy environments.     

Speech recognition and comfort using hearing instruments with adaptive directional characteristics in asymmetric listening conditions

OBJECTIVE: Hearing instruments with adaptive directional microphone systems attempt to maximize speech-to-noise ratio (SNR) and thereby improve speech recognition in noisy backgrounds. When instruments with adaptive systems are fitted bilaterally, there is the potential for adverse effects as they operate independently and may give confusing cues or disturbing effects. The present study compared speech recognition performance in 16 listeners fitted bilaterally with the Phonak Claro hearing instrument using omni-directional, fixed directional, and adaptive directional microphone settings as well as mixed microphone settings (an omni-directional microphone on one side and an adaptive directional microphone on the other). DESIGN: Under anechoic conditions, speech was always presented from a loudspeaker directly in front of the listener (0 degree azimuth) whereas noise was presented from one or two loudspeakers arranged either symmetrically (0, 180, 90 + 270 degrees) or asymmetrically (170 + 240 degrees and 120 + 190 degrees) in the horizontal plane. Adaptive sentence recognition in noise measurement was supplemented by quality ratings. RESULTS: With symmetrical omni-directional settings (Omni/Omni), performance was poorer than a control group of 14 listeners with normal hearing tested unaided: Aided listeners required 4.3 dB more favorable SNR for criterion performance. In all loudspeaker arrangements in which directional characteristics could be exploited, performance with symmetrical adaptive microphones (Adapt/Adapt) was similar to the control group. The mixed microphone settings did not appear to confer any particular disadvantage for speech recognition from their asymmetric nature, always giving scores significantly better than Omni/Omni. Quality rating scores were consistent with speech recognition performance, showing benefits in terms of clarity and comfort for the Adapt/Adapt and Fixed/Fixed microphone conditions over the Omni/Omni and mixed microphone conditions wherever directional characteristics could be used. Similarly, the mixed microphone conditions were rated more comfortable and quieter for the noise than Omni/Omni. CONCLUSIONS: It is concluded that bilateral hearing instruments with adaptive directional microphones confer benefits in terms of speech recognition in noise and sound quality. Independence of the two adaptive control systems does not appear to cause untoward effects.     

Impact of compression and hearing aid style on directional hearing aid benefit and performance.

OBJECTIVE: To evaluate the impact of low-threshold compression and hearing aid style (in-the-ear [ITE] versus behind-the-ear [BTE]) on the directional benefit and performance of commercially available directional hearing aids. DESIGN: Forty-seven adult listeners with mild-to-moderate sensorineural hearing loss were fit bilaterally with one BTE and four different ITE hearing aids. Speech recognition performance was measured through the Connected Speech Test (CST) and Hearing in Noise Test (HINT) for a simulated noisy restaurant environment. RESULTS: For both the HINT and CST, speech recognition performance was significantly greater for subjects fit with directional in comparison with omnidirectional microphone hearing aids. Performance was significantly poorer for the BTE instrument in comparison with the ITE hearing aids when using omnidirectional microphones. No differences were found for directional benefit between compression and linear fitting schemes. CONCLUSIONS: No systematic relationship was found between the relative directional benefit and hearing aid style; however, the speech recognition performance of the subjects was somewhat predictable based on Directivity Index measures of the individual hearing aid models. The fact that compression did not interact significantly with microphone type agrees well with previously reported electroacoustic data.     

Multi-microphone technology for severe-to-profound hearing loss

In this study the potential benefit of hearing instruments with multi-microphone technology was investigated in laboratory and in field tests for users with severe-to-profound hearing loss. Twenty-one experienced hearing aid users were fitted with high-power multi-microphone hearing instruments (Phonak PowerZoom P4 AZ). The following evaluations were performed: (i) adaptive speech test (SRT for HSM sentence test) in quiet and in noise with their own instrument and the test instrument in the omnidirectional (basic program) and directional mode (party noise profound+zoom algorithm). (ii) Paired comparisons of loudness, sound quality and speech intelligibility for both the omni and zoom program. (iii) Questionnaires on satisfaction and self-assessment of communication in different listening conditions (Oldenburg Inventory). Only 10 subjects achieved 50% correct (SRT) on the sentence test in noise (speech 0 degrees/noise 180 degrees) with both their own instrument and the test instrument in the omnidirectional mode. However, 15 subjects succeeded in the SRT measurement in the directional mode. The average SRT improvement of the directional over the omnidirectional mode was 13.7 dB. Loudness was judged 'medium loud' for both listening programs. Sound quality and intelligibility were rated significantly better for the zoom program. Compared to their own instrument users' satisfaction with the test instrument was significantly higher, especially in noisy listening situations.     

Full time directional versus user selectable microphone modes in hearing aids

OBJECTIVE: The purpose of this experiment was to systematically examine hearing aid benefit as measured by speech recognition and self-assessment methods across omnidirectional and directional hearing aid modes. These data were used to compare directional benefit as measured by speech recognition in the laboratory to hearing aid wearer's perceptions of benefit in everyday environments across full-time directional, full-time omnidirectional, and user selectable directional fittings. Identification of possible listening situations that resulted in different self reported hearing aid benefit as a function of microphone type was a secondary objective of this experiment. DESIGN: Fifteen adults with symmetrical, sloping sensorineural hearing loss were fitted bilaterally with in-the-ear (ITE) directional hearing aids. Measures of hearing aid benefit included the Profile of Hearing Aid Benefit (PHAB), the Connected Sentence Test (CST), the Hearing in Noise Test (HINT), and a daily use log. Additionally, two new subscales were developed for administration with the PHAB. These subscales were developed to specifically address situations in which directional hearing aids may provide different degrees of benefit than omnidirectional hearing aids. Participants completed these measures in three conditions: omnidirectional only (O), directional only with low-frequency gain compensation (D), and user-selectable directional/omnidirectional (DO). RESULTS: Results from the speech intelligibility in noise testing indicated significantly more hearing aid benefit in directional modes than omnidirectional. PHAB results indicated more benefit on the background noise subscale (BN) in the DO condition than in the O condition; however, this directional advantage was not present for the D condition. Although the reliability of the newly proposed subscales is as yet unknown, the data were interpreted as revealing a directional advantage in situations where the signal of interest was in front of the participant and a directional disadvantage in situations where the signal of interest was behind the listener or localization was required. CONCLUSIONS: Laboratory directional benefit is reflected in self-assessment measures that focus on listening in noise when the sound source of interest is in front of the listener. The use of a directional hearing aid mode; however, may have either a positive, a neutral, or a negative impact on hearing aid benefit measured in noisy situations, depending on the specific listening situation.     

Performance of directional microphones for hearing aids: real-world versus simulation

The purpose of this study was to assess the accuracy of clinical and laboratory measures of directional microphone benefit. Three methods of simulating a noisy restaurant listening situation ([1] a multimicrophone/multiloudspeaker simulation, the R-SPACE, [2] a single noise source behind the listener, and [3] a single noise source above the listener) were evaluated and compared to the "live" condition. Performance with three directional microphone systems differing in polar pattern (omnidirectional, supercardioid, and hypercardioid array) and directivity indices (0.34, 4.20, and 7.71) was assessed using a modified version of the Hearing in Noise Test (HINT). The evaluation revealed that the three microphones could be ordered with regard to the benefit obtained using any of the simulation techniques. However, the absolute performance obtained with each microphone type differed among simulations. Only the R-SPACE simulation yielded accurate estimates of the absolute performance of all three microphones in the live condition. Performance in the R-SPACE condition was not significantly different from performance in the "live restaurant" condition. Neither of the single noise source simulations provided accurate predictions of real-world (live) performance for all three microphones.     

Effects of noise source configuration on directional benefit using symmetric and asymmetric directional hearing aid fittings

OBJECTIVE: The benefits of directional processing in hearing aids are well documented in laboratory settings. Likewise, substantial research has shown that speech understanding is optimized in many settings when listening binaurally. Although these findings suggest that speech understanding would be optimized by using bilateral directional technology (e.g., a symmetric directional fitting), recent research suggests similar performance with an asymmetrical fitting (directional in one ear and omnidirectional in the other). The purpose of this study was to explore the benefits of using bilateral directional processing, as opposed to an asymmetric fitting, in environments where the primary speech and noise sources come from different directions. DESIGN: Sixteen older adults with mild-to-severe sensorineural hearing loss (SNHL) were recruited for the study. Aided sentence recognition using the Hearing in Noise Test (HINT) was assessed in a moderately reverberant room, in three different speech and noise conditions in which the locations of the speech and noise sources were varied. In each speech and noise condition, speech understanding was assessed in four different microphone modes (bilateral omnidirectional mode; bilateral directional mode; directional mode left and omnidirectional mode right; omnidirectional mode left and directional mode right). The benefits and limitations of bilateral directional processing were assessed by comparing HINT thresholds across the various symmetric and asymmetric microphone processing conditions. RESULTS: Study results revealed directional benefit varied based on microphone mode symmetry (i.e., symmetric versus asymmetric directional processing) and the specific speech and noise configuration. In noise configurations in which the speech was located in the front of the listener and the noise was located to the side or surrounded the listener, maximum directional benefit (approximately 3.3 dB) was observed with the symmetric directional fitting. HINT thresholds obtained when using bilateral directional processing were approximately 1.4 dB better than when an asymmetric fitting (directional processing in only one ear) was used. When speech was located on the side of the listener, the use of directional processing on the ear near the speech significantly reduced speech understanding. CONCLUSIONS: Although directional benefit is present in asymmetric fittings, the use of bilateral directional processing optimizes speech understanding in noise conditions in which the speech comes from in front of the listener and the noise sources are located to the side of or surround the listener. In situations in which the speech is located to the side of the listener, the use of directional processing on the ear adjacent to the speaker is likely to reduce speech audibility and thus degrade speech understanding.     

Long-term usage of modern signal processing by listeners with severe or profound hearing loss: a retrospective survey

PURPOSE: To investigate the long-term benefit of multichannel wide dynamic range compression (WDRC) alone and in combination with directional microphones and noise reduction/speech enhancement for listeners with severe or profound hearing loss. METHOD: At the conclusion of a research project, 39 participants with severe or profound hearing loss were fitted with WDRC in one program and WDRC with directional microphones and speech enhancement enabled in a 2nd program. More than 2 years after the 1st participants exited the project, a retrospective survey was conducted to determine the participants' use of, and satisfaction with, the 2 programs. RESULTS: From the 30 returned questionnaires, it seems that WDRC is used with a high degree of satisfaction in general everyday listening situations. The reported benefit from the addition of a directional microphone and speech enhancement for listening in noisy environments was lower and varied among the users. This variable was significantly correlated with how much the program was used. CONCLUSIONS: The less frequent and more varied use of the program with directional microphones and speech enhancement activated in combination suggests that these features may be best offered in a 2nd listening program for listeners with severe or profound hearing loss.     

Effect of type of noise and loudspeaker array on the performance of omnidirectional and directional microphones

Differences in performance between omnidirectional and directional microphones were evaluated between two loudspeaker conditions (single loudspeaker at 180 degrees; diffuse using eight loudspeakers set 45 degrees apart) and two types of noise (steady-state HINT noise; R-Space restaurant noise). Twenty-five participants were fit bilaterally with Phonak Perseo hearing aids using the manufacturer's recommended procedure. After wearing the hearing aids for one week, the parameters were fine-tuned based on subjective comments. Four weeks later, differences in performance between omnidirectional and directional microphones were assessed using HINT sentences presented at 0 degrees with the two types of background noise held constant at 65 dBA and under the two loudspeaker conditions. Results revealed significant differences in Reception Thresholds for Sentences (RTS in dB) where directional performance was significantly better than omnidirectional. Performance in the 180 degrees condition was significantly better than the diffuse condition, and performance was significantly better using the HINT noise in comparison to the R-Space restaurant noise. In addition, results revealed that within each loudspeaker array, performance was significantly better for the directional microphone. Looking across loudspeaker arrays, however, significant differences were not present in omnidirectional performance, but directional performance was significantly better in the 180 degrees condition when compared to the diffuse condition. These findings are discussed in terms of results reported in the past and counseling patients on the potential advantages of directional microphones as the listening situation and type of noise changes.     

An evaluation of the performance of two binaural beamformers in complex and dynamic multitalker environments

Objective: Binaural beamformers are super-directional hearing aids created by combining microphone outputs from each side of the head. While they offer substantial improvements in SNR over conventional directional hearing aids, the benefits (and possible limitations) of these devices in realistic, complex listening situations have not yet been fully explored. In this study we evaluated the performance of two experimental binaural beamformers. Design: Testing was carried out using a horizontal loudspeaker array. Background noise was created using recorded conversations. Performance measures included speech intelligibility, localization in noise, acceptable noise level, subjective ratings, and a novel dynamic speech intelligibility measure. Study sample: Participants were 27 listeners with bilateral hearing loss, fitted with BTE prototypes that could be switched between conventional directional or binaural beamformer microphone modes. Results: Relative to the conventional directional microphones, both binaural beamformer modes were generally superior for tasks involving fixed frontal targets, but not always for situations involving dynamic target locations. Conclusions: Binaural beamformers show promise for enhancing listening in complex situations when the location of the source of interest is predictable.