Hearing In Noise Research Articles

An electronic windscreen for microphones

Wind-noise pickup in microphones can be highly disturbing, especially for directional microphones that attain their directivity by using velocity or spatial derivatives of the acoustic pressure. Since small directional microphones are common in audio communications systems, the problem of wind noise is well known and the typical solution is to use a windscreen. Conventional windscreens that block the wind but do not significantly alter the sound field can be very effective, but need to be relatively large to attain a good reduction in wind-noise pick-up. Small directional microphone arrays are more commonly used in hearing aids since they have been clinically shown to improve hearing in noise for hearing-impaired users. Since hearing aids are required to be compact, an effective conventional windscreen is not practical. This talk describes a novel multi-microphone wind-noise reduction algorithm that we refer to as an ‘‘electronic windscreen.’’ This new algorithm and its variants have low computational cost and are therefore applicable to commercial digital hearing aids that use multi-microphone arrays to attain directionality.

Protection and Enhancement of Hearing in Noise

Humans are subjected to noise in many occupational, military, transportation, recreational, and other settings, sometimes with attendant ill effects. Some noises may pose the threat of inducing hearing loss; most noises compromise one's ability to hear signals and other desirable sounds, as well as to communicate via speech. In this chapter, we review the role of noise in human hearing impairment and its effects on signal audibility and speech intelligibility, task performance, and nonauditory responses. Particular emphasis is paid to the needs of the human factors/ergonomics practitioner who is confronted with the objective of protecting individuals' hearing in noise, designing signals so that they are audible and recognizable, and in general, optimizing the use of the auditory sense under poor acoustic conditions. In addition to providing guidance and consensus standards for auditory danger signal design, we provide a review of new technologies in augmented hearing protection. These technologies are aimed at protecting the user's hearing in noise from injury while affording improved audibility for certain applications.

The Effect of Speech Presentation Level on Acceptance of Background Noise in Listeners with Normal Hearing

A method has been established to measure the maximum acceptable background noise level (BNL) for a listener, while listening to speech at the most comfortable listening level (MCL). The acceptable noise level (ANL) is the difference between BNL and MCL. In the present study, the ANL procedure was used to measure acceptance of noise, first, in the presence of speech at MCL and, then, for speech presented at much lower and higher levels in listeners with normal hearing. This study used the term ANL to describe the results obtained at MCL and also at other speech presentation levels. The mean ANL at MCL was 15.5 dB, which is comparable to results obtained by previous investigators. ANL increases systematically with speech presentation level. Mean ANLs ranged from 10.6 dB when speech was presented at 20 dB HL to 24.6 dB when speech was presented at 76 dB HL. The results indicated that the acceptance of noise depends significantly on speech presentation level.

Hearing sensitivity and critical ratios of hooded crows (Corvus corone cornix)

The hearing threshold and critical ratios were estimated psycho-acoustically for captive wild-caught hooded crows by a yes/no procedure and the method of constant stimuli. Human subjects were tested in the same setup for direct comparison and to check for experimental artifacts. The hooded crows were found to have excellent low-frequency hearing capabilities compared to other passerine birds. Their hearing sensitivity is very close to that of humans at and below 5.6 kHz. The distribution of the critical ratios differed from that of the average bird and humans in being rather constant with frequency and not increasing monotonically. It furthermore showed a middle region of 5-6 dB lower critical ratio values between 500 Hz and 2 kHz. It is suggested that this improved range for hearing in noise is an adaptation to long distance communication. Human critical ratios gave the expected values and were between 3 and 6 dB lower than those of the crows.

Development and Validation of the Effectiveness of Auditory Rehabilitation Scale

To develop a new scale of hearing-related function and quality of life in patients with hearing aids that addresses overlooked concerns, such as hearing-aid comfort, convenience, and cosmetic appearance, that may influence hearing-aid adherence while maintaining brevity and sensitivity to clinical change. Prospective, multicenter instrument validation. Four diverse sites in Washington State, including 2 private practices, 1 university setting, and 1 Veterans Affairs hospital. Seventy-eight patients with hearing aids. We created 2 modules in the Effectiveness of Auditory Rehabilitation (EAR) scale. The first module (Inner EAR) covers intrinsic hearing issues such as hearing in quiet and hearing in noise and is administered both before and after treatment. The second module (Outer EAR) covers extrinsic (hearing-aid related) issues such as comfort, appearance, and convenience and is administered after hearing-aid fitting. Both scales were developed and validated in 3 stages. Stage 1 used a qualitative approach from multiple data sources to develop preliminary instruments. Stage 2 used approaches from classic test theory to reduce the number of items and psychometrically validate the instruments. Stage 3 examined the responsiveness or sensitivity to clinical change. A 10-item Inner EAR module and a 10-item Outer EAR module were created and validated. Internal consistency of individual domains (Cronbach alpha = 0.85 and 0.72, respectively) and test-retest reliability (intraclass correlation coefficients = 0.76 and 0.81, respectively) were excellent. Evidence of construct validity included concurrent validity with other hearing scales and global visual analog scales, discriminant validity with dizziness handicap, correlation with hearing-aid adherence, and confirmatory factor analyses. Both scales had strong evidence of responsiveness (sensitivity to change), with higher effect sizes and Guyatt responsiveness statistics than the 2 widely used hearing scales in this study. The scales took an average of 5 minutes to complete. The EAR scale is a valid and reliable measure of the effectiveness of amplification in the treatment of sensorineural hearing loss. It addresses the range of issues that are of importance to hearing-aid patients. The scales have excellent psychometric properties, are more responsive than several widely used hearing scales, and are minimally burdensome for patients to complete. The EAR may be a valuable outcome measure in future studies of both existing hearing aids and newer hearing-aid technologies, such as bone-anchored aids or middle ear implants.

Hearing in noise with the Vibrant Soundbridge middle-ear implant

Hearing in noise with the Vibrant Soundbridge middle-ear implant

Physiological aspects regarding bilateral fitting of BAHAs

Normally, when we hear a sound, the sound is transmitted through the outer and middle ear to the inner ear where the sound energy is converted to nerve impulses. These impulses are transmitted further to the cochlear nucleus and superior olivary complex where information from both ears is mixed, compared and analysed. It is here the binaural process occur which allows us to determine the direction of the sound source as well as improve hearing in noise when the useful sound source and noise source is spatially separated. Hence, a patient with a bilateral hearing loss and fitted with airconduction (AC) hearing aids generally benefits from binaural fitting compared with monaural fitting. When a bone-anchored hearing aid (BAHA) is used, the sound is transmitted via bone conduction (BC) to the inner ear. The difference between the stimulation level of the contralateral and ipsilateral cochlea, often referred to as the transcranial attenuation, is normally in the range of 0–20 dB for frequencies up to 10 kHz. Hence, the side-specific stimulation of the inner ears is less with BC than with AC, which affects the binaural effect of the hearing. Due to the overhearing between the cochleae with BC, it is questionable whether binaural hearing is possible using BC stimulation and, consequently, BAHAs. Proceedings of the 4th International Symposium on Electronic Implants in Otology 83

Hearing in noise with the Vibrant Soundbridge middle-ear implant

Hearing in noise with the Vibrant Soundbridge middle-ear implant

Physiological aspects regarding bilateral fitting of BAHAs

Normally, when we hear a sound, the sound is transmitted through the outer and middle ear to the inner ear where the sound energy is converted to nerve impulses. These impulses are transmitted further to the cochlear nucleus and superior olivary complex where information from both ears is mixed, compared and analysed. It is here the binaural process occur which allows us to determine the direction of the sound source as well as improve hearing in noise when the useful sound source and noise source is spatially separated. Hence, a patient with a bilateral hearing loss and fitted with airconduction (AC) hearing aids generally benefits from binaural fitting compared with monaural fitting. When a bone-anchored hearing aid (BAHA) is used, the sound is transmitted via bone conduction (BC) to the inner ear. The difference between the stimulation level of the contralateral and ipsilateral cochlea, often referred to as the transcranial attenuation, is normally in the range of 0–20 dB for frequencies up to 10 kHz. Hence, the side-specific stimulation of the inner ears is less with BC than with AC, which affects the binaural effect of the hearing. Due to the overhearing between the cochleae with BC, it is questionable whether binaural hearing is possible using BC stimulation and, consequently, BAHAs. Proceedings of the 4th International Symposium on Electronic Implants in Otology 83

Binaurality in Middle Ear Implant Recipients Using Contralateral Digital Hearing Aids

For some patients, conventional hearing aids might have disadvantages that clearly limit the benefit of using them. The middle ear implant, Vibrant Soundbridge hearing prosthesis offers an approach to help such patients. Our study's objective was to identify the binaurality in a well-fitted digital hearing aid worn in the contralateral ear in recipients experienced with use of the Vibrant Soundbridge middle ear implant device. In a prospective study, warble-tone thresholds and stereophony were evaluated for the following conditions: (1) binaural unaided-with the middle ear implant inactive and the behind-the-ear hearing aid removed; (2) middle ear implant alone-middle ear implant active, behind-the-ear hearing aid removed; (3) middle ear implant plus behind-the-ear omnidirectional-middle ear implant active, behind-the-ear active; and (4) behind-the-ear omnidirectional alone-middle ear implant inactive, behind-the-ear omnidirectional active. Behind-the-ear omnidirectional and behind-the-ear is defined as the behind-the-ear active in the omnidirectional or directional response, respectively. Behind-the-ear is a contralateral digital hearing aid to the middle ear implant. Benefits such as improved sound detection, speech perception in quiet and in noise, and sound quality were investigated. The evaluation of subjective hearing benefit was based on the Abbreviated Profile of Hearing Aid Benefit (APHAB) test. Paired t tests (subject) were used to analyze the differences between mean thresholds for the different test conditions. Tertiary referral center. Eight adults (aged 45-68 yr) had undergone implantation with a single Vibrant Soundbridge at least 12 months before starting the study. These eight subjects presented no contraindication for contralateral hearing aid use. Patients were fitted 5 weeks before testing with a Siemens Signia digital behind-the-ear hearing aid in the side contralateral to the Vibrant Soundbridge. Five weeks after use of the contralateral hearing aid together with the middle ear implant, mean differences in warble-tone thresholds between Conditions 2 and 3 and between Conditions 3 and 4 were both statistically significant. The mean differences in speech reception thresholds were in line with the mean differences in average warble-tone thresholds. The mean speech reception threshold for the middle ear implant plus behind-the-ear omnidirectional condition was slightly worse (3 dB) than that for the middle ear implant alone condition; however, this difference was not statistically significant. Whereas speech reception threshold difference between Condition 1 and Condition 4 was not statistically significant (60 dB and 61 dB, respectively). The mean difference for the 0-degree azimuth alone was statistically significant (p < 0.05) for the conditions middle ear implant alone and middle ear implant plus behind-the-ear omnidirectional. The middle ear implant alone appears to give good sensitivity at 2 kHz for any direction. Increasing scores indicate greater percentages of problems. Percentages of problems were on average lower for the middle ear implant when used with the contralateral digital hearing aid based on the global score. The use of a middle ear implant Vibrant Soundbridge together with a contralateral digital hearing aid improved functional gain and speech perception thresholds in quiet, especially for the sound coming from the front of the patient. The use of a middle ear implant together with a contralateral digital hearing did not significantly improve hearing in noise.

Combined Electric and Acoustic Stimulation of the Auditory System: Results of a Clinical Study

Combined electric and acoustic stimulation (EAS) of the auditory system is a new therapy for patients with severe to profound high- and mid-frequency hearing loss but remaining low-frequency hearing. In a prospective study, 13 patients with low-frequency hearing of better than 60 dB below 1 kHz were implanted with a MED-EL COMBI 40+ cochlear implant. Pure tone thresholds as well as monosyllabic word scores and Hochmair-Schulz-Moser sentences in quiet and in noise were measured with hearing aids, cochlear implant alone and in the combined stimulation mode (EAS) in the same ear. Hearing could be partially preserved in 11 out of the 13 patients. All patients scored significantly higher with cochlear implant alone than with hearing aids. Seven patients scored higher in the EAS mode than with cochlear implant alone for sentences in noise, 4 remained unchanged, and 2 could not use EAS. Synergistic effects of EAS were most prominent for hearing in noise with increases of up to 72% as compared to cochlear implant alone.

Coherent modulation enhancement: Improving performance in noise for hearing aids and cochlear implants

Difficulty hearing in noise is a pervasive problem for hearing-impaired listeners. One approach is to digitally reduce noise using a modulation filter, which can selectively modify the time envelope of selected spectral bands. Previous approaches to modulation filtering, such as those based upon a Hilbert transform magnitude, increased signal distortion. A new coherent approach was used to determine a fixed and an optimal adaptive modulation filter. The optimal adaptive filter used information from the target speech to design the modulation filter. Threshold signal-to-noise ratio was measured adaptively using a spondee-in-noise task [Turner et al., J. Acoust. Soc. Am. 115, 1729 (2004)]. Subjects selected the spondee heard in a forced-choice task with a two-talker babble background. The spondee level was fixed at the listeners most comfortable level and noise level adjusted adaptively using a 2 dB step size, with threshold based on 10 reversals. Sensorineural hearing-impaired listeners completed three conditions: unprocessed speech; fixed modulation filter; and optimal adaptive modulation filter. Normal-hearing subjects heard a parallel set of conditions processed to simulate a 6-channel cochlear implant. There was significant improvement in threshold signal-to-noise ratio with the optimal adaptive filter for both groups. There was no improvement for the fixed modulation filter relative to unprocessed speech.

Bilateral fitting of BAHAs and BAHA® fitted in unilateral deaf persons: Acoustical aspectsAdaptación bilateral de BAHA y adaptación de BAHA en sorderas unilaterales: Aspectos acústicos

The benefit of a bone-anchored hearing aid (BAHA) to a patient fitted bilaterally; and the benefit of a BAHA®to a unilaterally deaf person was estimated by four acoustical measurements: directional sensitivity of a BAHA® placed at the skull, vibration transmission in the skull, gain, and estimated transcranial attenuation of bone conducted sound. Provided a patient has a similar bone conduction hearing ability at both cochlea, it was found that a patient should, theoretically, benefit from bilateral fitting of BAHAs in terms of better hearing thresholds from the front, and better overall hearing ability from the surround. The data indicates further, that bilateral fitting facilitates extraction of interaural cues, which should lead to greater ability to determine the direction of a sound source, as well as better hearing in noise. However, due to the cross-hearing of bone conducted sound, the binaural processing for the patient fitted bilaterally with BAHAs is less than for normal binaural air conduction hearing. Finally, the data showed that the benefit of fitting a BAHA® in a unilaterally deaf person, depends on that person's transcranial attenuation.

A cochlear implant user's guide to assistive devices and telephones

A cochlear implant user's guide to assistive devices and telephones

Research directions for future generations of cochlear implants

Physiological and psychophysical research indicates that improved hearing in noise and music appreciation are likely with cochlear implants, with better reproduction of the fine temporospatial patterns of neural response in the auditory pathways due to phase differences in neuron firing patterns as the result of the basilar membrane travelling wave. An initial speech-processing strategy, to in part reproduce this information, is showing better frequency discrimination and musical perception. However, more exact reproduction is likely with a new generation electrode array which could involve the use of neurotrophins and inherently conducting polymers. The siting and design of this, as well as safety, needs further investigation before it is implemented.

Research directions for future generations of cochlear implants

Physiological and psychophysical research indicates that improved hearing in noise and music appreciation are likely with cochlear implants, with better reproduction of the fine temporospatial patterns of neural response in the auditory pathways due to phase differences in neuron firing patterns as the result of the basilar membrane travelling wave. An initial speech-processing strategy, to in part reproduce this information, is showing better frequency discrimination and musical perception. However, more exact reproduction is likely with a new generation electrode array which could involve the use of neurotrophins and inherently conducting polymers. The siting and design of this, as well as safety, needs further investigation before it is implemented.

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

ObjectiveTo assess the advantages of binaural hearing for cochlear implant (CI) users using a hearing aid (HA) for thecontralateral ear.Material and MethodsThe subjects comprised 3 males and 3 females (age range 48–84 years). All of them had been using aCI and HA for >6 months. Their speech perception was examined in quiet using monosyllables and Japanese Hearing inNoise Test (J-HINT) sentences. Speech perception in noise was examined using J-HINT sentences. Late cortical waves weremeasured 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.ResultsThree subjects showed significantly better results for binaural than monaural (CI alone) hearing for monosyllablesand HINT sentences (p<0.05; paired t-test). Subjects with better speech perception had been using an HA for longer thanthose with poor performance (18.3 vs 4.0 years). The overall average score was better for binaural than monaural hearing inthe speech perception test under quiet and noisy conditions. Comparison of the latency of the P300 wave under monauraland binaural hearing conditions showed a significantly shorter latency for the latter (p=0.02; paired t-test).ConclusionAlthough the use of an HA alone showed marginal benefit for CI users, binaural hearing (CI + HA) resulted ina significant improvement in speech perception under various circumstances.

The performance-perceptual test and its relationship to unaided reported handicap.

Measurement of hearing aid outcomes is necessary for demonstration of treatment efficacy, third-party payment, and cost-benefit analysis. Outcomes are usually measured with hearing-related questionnaires and/or tests of speech recognition. However, results from these two types of test often conflict. In this paper, we provide data from a new test measure, known as the Performance-Perceptual Test (PPT), in which subjective and performance aspects of hearing in noise are measured using the same test materials and procedures. A Performance Speech Reception Threshold (SRTN) and a Perceptual SRTN are measured using the Hearing In Noise Test materials and adaptive procedure. A third variable, the discrepancy between these two SRTNs, is also computed. It measures the accuracy with which subjects assess their own hearing ability and is referred to as the Performance-Perceptual Discrepancy (PPDIS). One hundred seven subjects between 24 and 83 yr of age took part. Thirty-three subjects had normal hearing, while the remaining seventy-four had symmetrical sensorineural hearing loss. Of the subjects with impaired hearing, 24 wore hearing aids and 50 did not. All subjects underwent routine audiological examination and completed the PPT and the Hearing Handicap Inventory for the Elderly/Adults on two occasions, between 1 and 2 wk apart. The PPT was conducted for unaided listening with the masker level set to 50, 65, and 80 dB SPL. PPT data show that the subjects with normal hearing have significantly better Performance and Perceptual SRTNs at each test level than the subjects with impaired hearing but that PPDIS values do not differ between the groups. Test-retest reliability for the PPT is excellent (r-values > 0.93 for all conditions). Stepwise multiple regression analysis showed that the Performance SRTN, the PPDIS, and age explain 40% of the variance in reported handicap (Hearing Handicap Inventory for the Elderly/Adults scores). More specifically, poorer performance, underestimation of hearing ability and younger age result in greater reported handicap, and vice versa. Reported handicap consists of a performance component and a (mis)perception component, as measured by the Performance SRTN and the PPDIS respectively. The PPT should thus prove to be a valuable tool for better understanding why some individuals complain of hearing difficulties but have only a mild hearing loss or conversely report few difficulties in the presence of substantial impairment. The measure would thus seem to provide both an explanation and a counseling tool for patients for whom there is a mismatch between reported and measured hearing difficulties.

Reduced Medial Olivocochlear Bundle System Function in Children with Auditory Processing Disorders

A common complaint of children with auditory processing disorders (APD) is difficulty in understanding speech in the presence of background noise. Evidence from animal and human studies has suggested that the medial olivocochlear bundle (MOCB) may play a role in hearing in noise. The MOCB function can be evaluated by the suppression effect of the transient evoked otoacoustic emissions (TEOAE) in response to contralateral acoustic stimulation (CAS). The present study was conducted to investigate the suppression effect of TEOAE in APD children. The study groups comprised 15 APD children aged 8–13 years associated with learning disabilities and 15 controls matched for gender and age. The suppression effect of TEOAE was evaluated by comparing the TEOAE levels with and without CAS. A significantly reduced suppression effect of TEOAE was demonstrated in the APD group, when compared to the controls. In addition, higher TEOAE levels were found in the APD group, suggesting inherent reduced MOCB activity on the outer hair cells in APD children. These results imply that some APD children present low activity of the MOCB system, which may indicate a reduced auditory inhibitory function and affect their ability to hear in the presence of background noise.

The effect of presentation level and compression characteristics on sentence recognition in modulated noise

The effect of fast-acting compression on speech recognitionin fully modulated (FUM) noise in listeners with normaland impaired hearing was investigated in two experiments. We wanted to determine the relationships between the benefitfrom compression and some audiological factors.Furthermore, the sensitivity to changes in compressionparameters was also evaluated. The results showed thattwo-thirds of the listeners performed worse with fast-actingcompression than with linear processing. Normal-hearinglisteners showed the most benefit from compression. A significantrelationship was found between benefit from compressionand speech-to-noise ratio at threshold (SNRT) inslightly modulated (SM) noise. Pure-tone threshold wasfound to be a weak predictor of benefit from compression.No relationship was found between benefit from compressionand the release of masking for the FUM noise. Thevariability in the results across different compressionparameters was related to SNRT in SM noise. The resultssuggest an inverse relationship between benefit from compressionand the severity of the suprathreshold hearing loss.