The effects of changes in head angle on auditory and visual input for omnidirectional and directional microphone hearing aids

Improving the signal-to-noise ratio (SNR) for individuals with hearing loss who are listening to speech in noise provides an obvious benefit. Although binaural hearing provides the greatest advantage over monaural hearing in noise, some individuals with symmetrical hearing loss choose to wear only one hearing aid. The present study tested the hypothesis that individuals with symmetrical hearing loss fit with one hearing aid would demonstrate improved speech recognition in background noise with increases in head turn. Fourteen individuals were fit monaurally with a Starkey Gemini in-the-ear (ITE) hearing aid with directional and omnidirectional microphone modes. Speech recognition performance in noise was tested using the audiovisual version of the Connected Speech Test (CST v.3). The test was administered in auditory-only conditions as well as with the addition of visual cues for each of three head angles: 0 degrees, 20 degrees, and 40 degrees. Results indicated improvement in speech recognition performance with changes in head angle for the auditory-only presentation mode at the 20 degrees and 40 degrees head angles when compared to 0 degrees. Improvement in speech recognition performance for the auditory + visual mode was noted for the 20 degrees head angle when compared to 0 degrees. Additionally, a decrement in speech recognition performance for the auditory + visual mode was noted for the 40 degrees head angle when compared to 0 degrees. These results support a speech recognition advantage for listeners fit with one ITE hearing aid listening in a close listener-to-speaker distance when they turn their head slightly in order to increase signal intensity.     

Listeners who prefer monaural to binaural hearing aids

Four patients who preferred monaural as compared with binaural amplification were evaluated. For these patients, audiometric data, recognition performance on a dichotic digit task, and monaural and binaural hearing aid performance using four amplification strategies (National Acoustic Laboratories-Revised, a speech in noise algorithm, multiple-microphone arrays, and frequency modulated [FM]) are described. The results of dichotic testing using a one-, two-, and three-pair dichotic digit task in free- and directed-recall conditions indicated a left-ear deficit for all subjects that could not be explained by peripheral auditory findings or by a cognitive-based deficit. The results of soundfield testing using a speech in multitalker babble paradigm indicated that when listening in noise, there was little difference between aided and unaided word-recognition performance, suggesting that the binaural hearing aids originally fit for each patient were not providing substantial benefit when listening in a competing babble background. Word-recognition performance when aided monaurally in the right ear was superior to performance when aided monaurally in the left ear and when aided binaurally. The only successful binaural amplification strategy was the FM system. The results indicate that listeners with an auditory-based deficit in dichotic listening may function better with a monaural hearing aid fitting or with an assistive listening device such as an FM system. The findings also suggest that a test of dichotic listening is an important component in the evaluation of patients being considered for amplification.     

双耳选配助听器的益处

人们生活中的绝大部分时间是处于多个声音和大量声反射面的复杂声学环境中，人的听觉系统需要不断地接受和处理声源与噪音或回声问的信息．目的是为了准确地定位．提高噪声环境下的言语清晰度以及抑制回声，双耳聆听系统在这些方面起到十分重要的作用。听力损失患者常常抱怨在复杂环境中无法听清语言从而导致交流困难．选配具有降噪技术的全数字助听器可以在一定程度上提高噪声环境下的言语清晰度，     

Comparison of performance across three directional hearing aids

This study compared the speech recognition performance of 12 hearing-impaired listeners fit with three commercially available behind-the-ear hearing aids in both directional and omnidirectional modes. One digitally programmable analog and two "true digital" hearing aids were selected as test instruments. Testing was completed in both "living room" and anechoic room environments. Speech recognition was examined using modified forms of the Hearing in Noise Test and the Nonsense Syllable Test. The single competing stimuli of these tests were replaced with five uncorrelated competing sources. Results revealed a significant speech recognition in noise advantage for all directional hearing aids in comparison to their omnidirectional counterparts. Maximum performance of the directional hearing aids did not significantly vary across circuit type, suggesting that processing differences did not affect maximum directional hearing aid performance. In addition, the results suggest that performance in one reverberant environment cannot be used to accurately predict performance in an environment with differing reverberation.     

Contribution of monaural and binaural cues to sound localization in listeners with acquired unilateral conductive hearing loss: improved directional hearing with a bone-conduction device

Sound localization in the horizontal (azimuth) plane relies mainly on interaural time differences (ITDs) and interaural level differences (ILDs). Both are distorted in listeners with acquired unilateral conductive hearing loss (UCHL), reducing their ability to localize sound. Several studies demonstrated that UCHL listeners had some ability to localize sound in azimuth. To test whether listeners with acquired UCHL use strongly perturbed binaural difference cues, we measured localization while they listened with a sound-attenuating earmuff over their impaired ear. We also tested the potential use of monaural pinna-induced spectral-shape cues for localization in azimuth and elevation, by filling the cavities of the pinna of their better-hearing ear with a mould. These conditions were tested while a bone-conduction device (BCD), fitted to all UCHL listeners in order to provide hearing from the impaired side, was turned off. We varied stimulus presentation levels to investigate whether UCHL listeners were using sound level as an azimuth cue. Furthermore, we examined whether horizontal sound-localization abilities improved when listeners used their BCD. Ten control listeners without hearing loss demonstrated a significant decrease in their localization abilities when they listened with a monaural plug and muff. In 4/13 UCHL listeners we observed good horizontal localization of 65 dB SPL broadband noises with their BCD turned off. Localization was strongly impaired when the impaired ear was covered with the muff. The mould in the good ear of listeners with UCHL deteriorated the localization of broadband sounds presented at 45 dB SPL. This demonstrates that they used pinna cues to localize sounds presented at low levels. Our data demonstrate that UCHL listeners have learned to adapt their localization strategies under a wide variety of hearing conditions and that sound-localization abilities improved with their BCD turned on.     

Benefit from binaural hearing aids in individuals with a severe hearing impairment

The relative benefits of binaural as opposed to monaural hearing aids were assessed by the use of a diotically presented, audiovisual speech-in-noise task in a group of bilateral, severely hearing-impaired individuals. Significantly greater benefit was gained from binaural amplification, irrespective of hearing level and degree of asymmetry. The benefit was considered to be due to central summation. It is concluded that binaural amplification should be attempted in all bilateral, severely hearing-impaired subjects. About 80% will accept this and be able to demonstrate benefit in an audiovisual task.     

Comparison of monaural and binaural hearing aid use on a trial period basis

Thirty hearing-impaired patients compared monaural and binaural hearing aid use for a period of 4 weeks. Most of them preferred binaural hearing aids in quiet situations, but monaural hearing aids in noisy environments. Follow-up at 6 months revealed that 17 had purchased monaural hearing aids, 8 had purchased binaural hearing aids.     

The bandwidth effect on monaural and binaural localization

Listeners located, monaurally and binaurally, an 8.0 kHz centered noise burst whose bandwidth was set at 2.0, 4.0, 6.0 and 8.0 kHz. Loudspeakers, placed 7.5 degrees apart, covered an arc extending from 15 degrees to 165 degrees to the left of midline. Listeners reported the number of that loudspeaker from which the noise bursts appeared. A significant reduction in localization errors was associated with increments in bandwidth and for binaural localization, this was attained largely through fewer instances of confusing sounds from the front with those from the rear. While overall, binaural accuracy exceeded monaural accuracy when sounds came from the front or rear, no appreciable differences between the two listening conditions were noted when the sounds came from the middle section of the arc. Only when broadband noise was employed, as it was in a supplementary set of observations, did binaural localization uniformly surpass monaural localization in accuracy - a finding attributed to the introduction of low frequencies which resulted in the addition of interaural ongoing phase differences to the constellation of localization cues.     

Performance in children with hearing aids or cochlear implants: bilateral stimulation and binaural hearing

It is well recognised that normal hearing people use their hearing in both ears to locate sounds and to understand speech in complex listening conditions. Whereas it is standard practice to provide two hearing aids to children with bilateral hearing loss, the situation with cochlear implantation is less certain. Questions remain as to what binaural aided functioning is possible for children who use a hearing aid and a cochlear implant in opposite ears (bimodal hearing). The first part of this paper draws on research at the National Acoustic Laboratories to show that children who used bimodal hearing devices obtained binaural advantages in localization. They could also take advantage of head shadow and binaural redundancy for speech intelligibility. The second part presents data showing that some hearing-impaired children may have binaural processing deficits even when bilateral stimulation is provided. Additional strategies may be necessary to develop or enable the use of binaural cues by these children.     

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.     

Long-term effects of monaural, binaural and no amplification in subjects with bilateral hearing loss

This study expands upon our earlier work by comparing initial PB scores and audiometric thresholds with results obtained 4-17 years later for subjects with bilateral sensorineural hearing losses who were monaurally aided (n = 48), binaurally aided (n = 19), or unaided (n = 19). Thresholds decreased slightly for all groups, but aided and unaided ears did not differ significantly in this respect, revealing no acoustic trauma effect due to hearing aid use. PB scores decreased significantly only for the unaided ear of the monaurally aided subjects, but not for their aided ear, or for the binaurally aided or unaided groups. These findings suggest an auditory deprivation effect for the unaided ear of those wearing a monaural hearing aid. Changes in PB scores were not correlated with duration between the two test dates. Changes in PB scores were correlated with degree of hearing loss only for the unaided group.     

Comparison of speech perception between monaural and binaural hearing in cochlear implant patients

Objective To assess the advantages of binaural hearing for cochlear implant (CI) users using a hearing aid (HA) for the contralateral ear.

Material and Methods The subjects comprised 3 males and 3 females (age range 48–84 years). All of them had been using a CI and HA for >6 months. Their speech perception was examined in quiet using monosyllables and Japanese Hearing in Noise Test (J-HINT) sentences. Speech perception in noise was examined using J-HINT sentences. Late cortical waves were measured while subjects listened to 1 kHz frequent and 2 kHz target tone stimuli. The latency of the event-related potential (P300) wave was compared for monaural and binaural hearing conditions.

Results Three subjects showed significantly better results for binaural than monaural (CI alone) hearing for monosyllables and HINT sentences (p<0.05; paired t-test). Subjects with better speech perception had been using an HA for longer than those with poor performance (18.3 vs 4.0 years). The overall average score was better for binaural than monaural hearing in the speech perception test under quiet and noisy conditions. Comparison of the latency of the P300 wave under monaural and binaural hearing conditions showed a significantly shorter latency for the latter (p=0.02; paired t-test).

Conclusion Although the use of an HA alone showed marginal benefit for CI users, binaural hearing (CI + HA) resulted in a significant improvement in speech perception under various circumstances.     

Comparison of speech perception between monaural and binaural hearing in cochlear implant patients

OBJECTIVE: To assess the advantages of binaural hearing for cochlear implant (CI) users using a hearing aid (HA) for the contralateral ear. MATERIAL AND METHODS: The subjects comprised 3 males and 3 females (age range 48-84 years). All of them had been using a CI and HA for > 6 months. Their speech perception was examined in quiet using monosyllables and Japanese Hearing in Noise Test (J-HINT) sentences. Speech perception in noise was examined using J-HINT sentences. Late cortical waves were measured while subjects listened to 1 kHz frequent and 2 kHz target tone stimuli. The latency of the event-related potential (P300) wave was compared for monaural and binaural hearing conditions. RESULTS: Three subjects showed significantly better results for binaural than monaural (CI alone) hearing for monosyllables and HINT sentences (p < 0.05; paired t-test). Subjects with better speech perception had been using an HA for longer than those with poor performance (18.3 vs 4.0 years). The overall average score was better for binaural than monaural hearing in the speech perception test under quiet and noisy conditions. Comparison of the latency of the P300 wave under monaural and binaural hearing conditions showed a significantly shorter latency for the latter (p = 0.02; paired t-test). CONCLUSIONS: Although the use of an HA alone showed marginal benefit for CI users, binaural hearing (CI+HA) resulted in a significant improvement in speech perception under various circumstances.     

Acceptance of noise with monaural and binaural amplification

The present study investigated the effects of monaural and binaural amplification on speech understanding in noise and acceptance of noise for 39 listeners with hearing impairment. Results demonstrated that speech understanding in noise improved with binaural amplification; however, acceptance of noise was not dependent on monaural or binaural amplification for most listeners. These results suggest that although two hearing aids maximize speech understanding ability in noise, most individuals' acceptance of noise, which is directly related to hearing aid use, may not be affected by the use of binaural amplification. It should be noted that monaural amplification resulted in greater acceptance of noise for some listeners, indicating that binaural amplification may negatively affect some individuals' willingness to wear hearing aids. It should also be noted that interaural differences in acceptance of noise might exist for some listeners; therefore, if only one hearing aid is fitted, monaural ANLs should be measured.     

Maturation of binaural interaction components in auditory brainstem responses of young guinea pigs with monaural or binaural conductive hearing loss

Summary Reversible conductive hearing loss created during the first 4 weeks post partum caused marked alterations in the maturation of binaural interaction components in the auditory brainstem responses of guinea pigs. In untreated control animals all three components investigated demonstrated postnatal development in terms of latency shortening that was completed during the first 3 weeks of life. Plugging of both external ear canals caused a significant delay in the maturation of the late component DN₂, where latency values of the controls were reached only 2 weeks after the end of the treatment, i.e. after 6 weeks of life. Monaural deprivation likewise led to a retarded development of peak latencies during the phase of imbalanced sensory imput. After the end of the one-sided conductive hearing loss the maturation process was markedly enhanced, even resulting in latency values for DN₂ and DP₁ that were significantly shorter than those of the controls. This phenomenon persisted until the end of the study period and was the case for both plugged and untreated ears in this group of animals. The time course of latencies in two other groups of experimental animals which were deprived in the same way as adults suggests that the effects observed are due to a sensitive period in the maturation process of the auditory pathway.     

Evaluation of model-based versus non-parametric monaural noise-reduction approaches for hearing aids

Abstract

Objective: Single channel noise reduction has been well investigated and seems to have reached its limits in terms of speech intelligibility improvement, however, the quality of such schemes can still be advanced. This study tests to what extent novel model-based processing schemes might improve performance in particular for non-stationary noise conditions. Design: Two prototype model-based algorithms, a speech-model-based, and a auditory-model-based algorithm were compared to a state-of-the-art non-parametric minimum statistics algorithm. A speech intelligibility test, preference rating, and listening effort scaling were performed. Additionally, three objective quality measures for the signal, background, and overall distortions were applied. For a better comparison of all algorithms, particular attention was given to the usage of the similar Wiener-based gain rule. Study sample: The perceptual investigation was performed with fourteen hearing-impaired subjects. Results: The results revealed that the non-parametric algorithm and the auditory model-based algorithm did not affect speech intelligibility, whereas the speech-model-based algorithm slightly decreased intelligibility. In terms of subjective quality, both model-based algorithms perform better than the unprocessed condition and the reference in particular for highly non-stationary noise environments. Conclusion: Data support the hypothesis that model-based algorithms are promising for improving performance in non-stationary noise conditions.     

The development of a biologically-inspired directional microphone for hearing aids

The development of novel micro-fabrication techniques for producing a directional microphone for hearing aids is here described. The mechanisms underlying both the structure and function of these unusual microphones were originally inspired by the ears of an inconspicuous insect, the parasitoid fly Ormia ochracea. The structure of Ormia's ears inspired new approaches to design directional microphones that are more sensitive and have lower thermal noise than that typical of those using traditional approaches. The mechanisms for directional hearing in this animal are discussed along with the engineering design concepts that they have inspired, because they illustrate how basic research can inspire technology development-translational research. However, to realize the potential of bio-exploitation this microphone diaphragm concept would have been very difficult to realize without the availability of new silicon micro-fabrication technologies. Thus, this report can be viewed as an example of what may be possible with the application of new fabrication methods to microphones. Challenges and opportunities provided by the use of silicon micro-fabrication technology for microphones are discussed.     

Speech understanding and directional hearing for hearing-impaired subjects with in-the-ear and behind-the-ear hearing aids

With respect to acoustical properties, in-the-ear (ITE) aids should give better understanding and directional hearing than behind-the-ear (BTE) aids. Also hearing-impaired subjects often prefer ITEs. A study was performed to assess objectively the improvement in speech understanding and directional hearing afforded by ITE aids versus BTEs. In 28 hearing-impaired subjects, who visited our Centre for a check-up of their ITEs, the following parameters were measured: (a) thresholds for third-octave bandpass noises between 0.25 and 4 kHz, (b) speech reception thresholds for short Dutch sentences in quiet and with background noise, (c) directional hearing. All three experiments were done binaurally with the subjects wearing their ITEs, BTEs, and no hearing aid. With the 2-cc coupler, the gain used by the subject was measured. The SRT values for the ITE were significantly lower than those for BTE. More gain at 2 and 4 kHz in the ITE proved to be a responsible factor for this improvement. Directional hearing was not improved by wearing an ITE. Large interindividual differences were found between functional gain and the 2-cc coupler measurements. The mean functional gain at 4 kHz for an ITE is higher than the gain measured in a 2-cc coupler. For a BTE, the functional gain at 2 and 4 kHz is lower than the 2-cc coupler gain.     

方向性麦克风技术在助听器中的应用

引言 目前，助听器的广泛使用已经使广大听力损失患者在很大程度上改善了他们的生活质量，但这些助听器用户在日常生活中还是会有一些聆听上的困难，尤其是在噪声环境下与人交谈。方向性麦克风系统（directional microphones system）也译为指向性麦克风，是用于提高助听器言语信噪比的一项重要技术，尤其能改善在噪声环境下的言语清晰度（可懂度）。本文通过介绍方向性麦克风的原理、作用以及实际应用方面等相关知识来帮助听力从业人员、技术人员和用户更好地了解和使用这项技术。