Evaluation of the sparse coding shrinkage noise reduction algorithm for the hearing impaired

Although there are numerous single-channel noise reduction strategies to improve speech perception in a noisy environment, most of them can only improve speech quality but not improve speech intelligibility for normal hearing (NH) or hearing impaired (HI) listeners. Exceptions that can improve speech intelligibility currently are only those that require a priori statistics of speech or noise. Most of the noise reduction algorithms in hearing aids are adopted directly from the algorithms for NH listeners without taking into account of the hearing loss factors within HI listeners. HI listeners suffer more in speech intelligibility than NH listeners in the same noisy environment. Further study of monaural noise reduction algorithms for HI listeners is required.The motivation is to adapt a model-based approach in contrast to the conventional Wiener filtering approach. The model-based algorithm called sparse coding shrinkage (SCS) was proposed to extract key speech information from noisy speech. The SCS algorithm was evaluated by comparison with another state-of-the-art Wiener filtering approach through speech intelligibility and quality tests using 9 NH and 9 HI listeners. The SCS algorithm matched the performance of the Wiener filtering algorithm in speech intelligibility and speech quality. Both algorithms showed some intelligibility improvements for HI listeners but not at all for NH listeners. The algorithms improved speech quality for both HI and NH listeners.Additionally, a physiologically-inspired hearing loss simulation (HLS) model was developed to characterize hearing loss factors and simulate hearing loss consequences. A methodology was proposed to evaluate signal processing strategies for HI listeners with the proposed HLS model and NH subjects. The corresponding experiment was performed by asking NH subjects to listen to unprocessed/enhanced speech with the HLS model. Some of the effects of the algorithms seen in HI listeners are reproduced, at least qualitatively, by using the HLS model with NH listeners.Conclusions: The model-based algorithm SCS is promising for improving performance in stationary noise although no clear difference was seen in the performance of SCS and a competitive Wiener filtering algorithm. Fluctuating noise is more difficult to reduce compared to stationary noise. Noise reduction algorithms may perform better at higher input signal-to-noise ratios (SNRs) where HI listeners can get benefit but where NH listeners already reach ceiling performance. The proposed HLS model can save time and cost when evaluating noise reduction algorithms for HI listeners

Determination and evaluation of clinically efficient stopping criteria for the multiple auditory steady-state response technique

Background: Although the auditory steady-state response (ASSR) technique utilizes objective statistical detection algorithms to estimate behavioural hearing thresholds, the audiologist still has to decide when to terminate ASSR recordings introducing once more a certain degree of subjectivity. Aims: The present study aimed at establishing clinically efficient stopping criteria for a multiple 80-Hz ASSR system. Methods: In Experiment 1, data of 31 normal hearing subjects were analyzed off-line to propose stopping rules. Consequently, ASSR recordings will be stopped when (1) all 8 responses reach significance and significance can be maintained for 8 consecutive sweeps; (2) the mean noise levels were ≤ 4 nV (if at this “≤ 4-nV” criterion, p-values were between 0.05 and 0.1, measurements were extended only once by 8 sweeps); and (3) a maximum amount of 48 sweeps was attained. In Experiment 2, these stopping criteria were applied on 10 normal hearing and 10 hearing-impaired adults to asses the efficiency. Results: The application of these stopping rules resulted in ASSR threshold values that were comparable to other multiple-ASSR research with normal hearing and hearing-impaired adults. Furthermore, in 80% of the cases, ASSR thresholds could be obtained within a time-frame of 1 hour. Investigating the significant response-amplitudes of the hearing-impaired adults through cumulative curves indicated that probably a higher noise-stop criterion than “≤ 4 nV” can be used. Conclusions: The proposed stopping rules can be used in adults to determine accurate ASSR thresholds within an acceptable time-frame of about 1 hour. However, additional research with infants and adults with varying degrees and configurations of hearing loss is needed to optimize these criteria

The effects of noise reduction technologies on the acceptance of background noise

The effect of noise reduction technologies in hearing aids on a listener\u27s acceptable noise level (ANL) was investigated. Technology designed to reduce noise within hearing aids; directional microphones (D-Mic), digital noise reduction algorithms (DNR) and the combination of the two technologies (Combo) were employed in the presence of three distinctly different background noises (single talker speech, speech shaped noise, and multi-talker babble). The same pair of twelve channel wide dynamic range compression behind-the-ear hearing instruments was fit on each of thirty participants. The hearing aids were set with four memories: no noise reduction technology activated (baseline), only D-Mic activated, only DNR activated, and the Combo of technologies activated. All other hearing aid settings and features remained the same across memories. Acceptable noise levels were investigated in each memory in the presence of each noise.In addition, subjective preference rankings of the noise reduction technology were obtained within each background noise (1= best, 3=worst). Listeners yielded significantly lower (better) ANL scores with Combo relative to D-Mic and DNR; and scores obtained with D-Mic were significantly better than those obtained with DNR. A technology x noise interaction was observed only for speech shaped noise in DNR, with listeners accepting significantly more noise in the presence of speech shaped noise than background noise containing speech. Listeners preferred D-Mic and Combo programs significantly more than DNR in the presence of single talker and multi-talker babble, and preferred Combo significantly more in the presence of speech shaped noise. Overall, listeners preferred the D-Mic and Combo programs equally as much and significantly more than DNR.In reviewing the preference data along with the ANL data, it is evident that improving an ANL with hearing aid technology is noticeable to listeners, at least when examined in this laboratory setting. These results indicate that listeners prefer noise technologies that improve their ability to accept noise

Perceptual Evaluation of Digital Signal Processing Strategies In a Modem Hearing Instrument Across Noisy and Reverberant Environments

Speech intelligibility and quality scores were evaluated across four different hearing aid settings that differed in the strength of directional microphone (DM), digital noise reduction (DNR), and level dependent speech enhancement (LDSE) features, in quiet and noise, and in low and high reverberation environments. Twenty-two listeners with bilateral sensorineural hearing loss and ten normal hearing listeners participated in our study. Results indicated that the directional microphone condition provided significant improvement for speech recognition in noise, at both levels of reverberation. Addition of SE and DNR processing to directional microphone had both beneficial and detrimental effects on speech perception and sound quality depending upon the strength of processing, type of environment, and noise condition. Specifically, SE and DNR features operating at maximum strength degraded speech intelligibility in the high reverberation environment. The same processing condition was, however, rated as having higher sound quality especially when the masker was stationary noise at 0 dB signal to noise ratio in low reverberation. Clinical implications of these results are discussed

DEVELOPMENT AND EVALUATION OF ENVELOPE, SPECTRAL AND TIME ENHANCEMENT ALGORITHMS FOR AUDITORY NEUROPATHY

Auditory neuropathy (AN) is a hearing disorder that reduces the ability to detect temporal cues in speech, thus leading to deprived speech perception. Traditional amplification and frequency shifting techniques used in modern hearing aids are not suitable to assist individuals with AN due to the unique symptoms that result from the disorder. This study proposes a method for combining both speech envelope enhancement and time scaling to combine the proven benefits of each algorithm. In addition, spectral enhancement is cascaded with envelope and time enhancement to address the poor frequency discrimination in AN. The proposed speech enhancement strategy was evaluated using an AN simulator with normal hearing listeners under varying degrees of AN severity. The results showed a significant increase in word recognition scores for time scaling and envelope enhancement over envelope enhancement alone. Furthermore, the addition of spectral enhancement resulted in further increase in word recognition at profound AN severity

The impact of directional listening on perceived localization ability

An important purpose of hearing is to aid communication. Because hearing-in-noise is of primary importance to individuals who seek remediation for hearing impairment, it has been the primary objective of advances in technology. Directional microphone technology is the most promising way to address this problem. Another important role of hearing is localization, allowing one to sense one's environment and feel safe and secure. The properties of the listening environment that are altered with directional microphone technology have the potential to significantly impair localization ability. The purpose of this investigation was to determine the impact of listening with directional microphone technology on individuals' self-perceived level of localization disability and concurrent handicap. Participants included 57 unaided subjects, later randomly assigned to participate in one of three aided groups of 19 individuals each, who used omni-directional microphone only amplification, directional microphone only amplification, or toggle-switch equipped hearing aids that allowed user discretion over the directional microphone properties of the instruments. Comparisons were made between the unaided group responses and those of the subjects after having worn amplification for three months. Additionally, comparisons between the directional microphone only group responses and each of the other two aided groups' responses were made. No significant differences were found. Hearing aids with omni-directional microphones, directional-only microphones, and those that are equipped with a toggle-switch, neither increased nor decreased the self-perceived level of ability to tell the location of sound or the level of withdrawal from situations where localization ability was a factor. Concurrently, directional-microphone only technology did not significantly worsen or improve these factors as compared to the other two microphone configurations. Future research should include objective measures of localization ability using the same paradigm employed herein. If the use of directional microphone technology has an objective impact on localization, clinicians might be advised to counsel their patients to be careful moving in their environment even though they do not perceive a problem with localization. If ultimately no significant differences in either objective or subjective measures are found, then concern over decreases in quality of life and safety with directional microphone use need no longer be considered

Acclimatation aux appareils auditifs par les personnes âgées avec perte auditive

Les aides auditives (AA) sont les principaux outils d’intervention de réadaptation recommandés aux personnes âgées ayant une perte auditive, car elles offrent un large éventail d’avantages. Cependant, beaucoup de personnes qui possèdent des AA ne les utilisent pas ou les sous-utilisent. La raison la plus récurrente exprimée par ces non-utilisateurs d’AA est la difficulté persistante à comprendre les conversations dans des environnements bruyants. Il n’est pas mentionné si ces personnes ont essayé de porter leurs AA pendant un certain temps avant de décider de ne plus les porter. Dans l’éventualité où elles auraient abandonné peu de temps après l’obtention de leurs AA, il est possible que ces individus n’aient pas bénéficié d’une adaptation optimale à l’environnement sonore, appelée acclimatation auditive. L’objectif principal de cette thèse est d’évaluer l’apport de l’expérience avec les AA sur l’acclimatation auditive. La première étude visait à déterminer, au moyen d'une revue systématique, si un effet d’acclimatation se produit après l’utilisation d’AA et, le cas échéant, à établir l’amplitude et l’évolution dans le temps de cet effet. Quatorze articles évaluant l’acclimatation via des mesures comportementales, d’auto-évaluation et électrophysiologiques répondaient aux critères d’inclusion et d’exclusion. Bien que leur qualité scientifique générale soit faible ou très faible, les résultats de la revue systématique appuient l’hypothèse qu’un effet d'acclimatation est présent, tel que documenté par les trois types de mesures. Pour la reconnaissance de la parole dans le bruit, l’amélioration varie entre 2 et 3 dB en termes de rapport signal sur bruit (RSB) sur une période minimale d'un mois. Cette étude met en évidence l'importance d’utiliser les AA après l’appareillage afin d’optimiser les bénéfices que celles-ci peuvent procurer. L’objectif du deuxième article était de rapporter les résultats d’une étude longitudinale pour déterminer si l’acclimatation aux AA des personnes âgées peut être évaluée par leurs performances à des tâches de reconnaissance de la parole dans le bruit ainsi que par des mesures d’effort auditif. Trente-deux nouveaux utilisateurs d’AA et 15 utilisateurs expérimentés ont été évalués sur une période de 38 semaines en utilisant un paradigme de double tâche. Pour les nouveaux utilisateurs, les résultats ont révélé une amélioration significative de 2 dB RSB sur un test de reconnaissance de la parole dans le bruit après quatre semaines d’utilisation des AA, et aucune diminution de l’effort auditif, tel que mesuré par le coût proportionnel de la double tâche et par le temps de réponse à la tâche secondaire. Chez les utilisateurs expérimentés, les résultats n’ont dévoilé aucune amélioration de leur performance de reconnaissance de la parole dans le bruit suite à l’utilisation des AA. En conclusion, les résultats confirment la présence d’un effet d’acclimatation tel qu’évalué par des mesures comportementales, d’auto-évaluation et électrophysiologiques suite à une utilisation régulière d’AA. Plus précisément, les nouveaux utilisateurs présentaient une amélioration cliniquement significative de 2 à 3 dB en termes de RSB après une utilisation régulière de leurs AA. Par conséquent, les nouveaux utilisateurs d’AA devraient être informés de cette possible amélioration au fil du temps, car cela pourrait les inciter à continuer de s’adapter à leurs AA plus longtemps avant de décider de les utiliser ou non.Hearing aids (HAs) are the primary rehabilitation intervention recommended for older adults with hearing loss, as they provide a wide range of benefits. However, a large proportion of individuals who own HAs does not use or underuse them. The most recurring reason reported by non-HA users is their difficulty to understand conversations in noisy environments even when they use HAs. It is unclear if these individuals tried to use their HAs for an extended period of time before abandoning their use. If they gave up too soon after being fitted with their HAs they may not have benefited from an auditory adaptation to the new auditory stimulation, referred to as auditory acclimatization. The main objective of this thesis is to evaluate the contribution of HA experience on auditory acclimatization. The first study aimed to determine, by means of a systematic review, if an acclimatization effect occurs after HA use and if so, to establish the magnitude and time-course of this effect. Fourteen articles that assessed acclimatization through behavioural, self-reported and physiological outcomes met the inclusion and the exclusion criteria. Although their general scientific quality was low or very low, the results of systematic review support the existence of an acclimatization effect as calculated by all three types of outcome measures. For speechrecognition- in-noise performance, improvement ranged from 2 to 3 dB in signal-to-noise ratio (SNR) over a minimum period of 1-month. This study highlights the importance of using the HAs on a regular basis after being fitted with HAs. The goal of the second study was to conduct a longitudinal investigation in order to determine whether acclimatization to HAs by older adults can be assessed data obtained on a speech-recognition-in-noise task and by measures of listening effort. Thirty-two new HA users and 15 experienced HA users were tested over a 38-week period using a dual-task paradigm. For new HA users, the results showed a significant improvement of 2 dB SNR on a speech-recognitionin- noise task after 4 weeks of using the HAs post fitting. Based on the proportional dual-task cost data and by the response time measures recorded on the secondary task. No improvement of speech perception performance in noise was observed for the experienced HA users. 8 The general findings from this thesis support the presence of an acclimatization effect as measured by behavioural, self-reported and physiological measures following regular HA use. Specifically, new HA users show a clinically significant change of 2 and 3 dB SNR on speechrecognition- in noise tasks following their initial fitting. Therefore, new HA users should be informed of the possible improvement in speech recognition over time, as it could entice them to pursue the use of their HAs for a longer period of time before deciding to abandon them