Understanding Speech In Noisy Environments Research Articles

Speech perception in tones and noise via cochlear implants reveals influence of spectral resolution on temporal processing.

Under normal conditions, human speech is remarkably robust to degradation by noise and other distortions. However, people with hearing loss, including those with cochlear implants, often experience great difficulty in understanding speech in noisy environments. Recent work with normal-hearing listeners has shown that the amplitude fluctuations inherent in noise contribute strongly to the masking of speech. In contrast, this study shows that speech perception via a cochlear implant is unaffected by the inherent temporal fluctuations of noise. This qualitative difference between acoustic and electric auditory perception does not seem to be due to differences in underlying temporal acuity but can instead be explained by the poorer spectral resolution of cochlear implants, relative to the normally functioning ear, which leads to an effective smoothing of the inherent temporal-envelope fluctuations of noise. The outcome suggests an unexpected trade-off between the detrimental effects of poorer spectral resolution and the beneficial effects of a smoother noise temporal envelope. This trade-off provides an explanation for the long-standing puzzle of why strong correlations between speech understanding and spectral resolution have remained elusive. The results also provide a potential explanation for why cochlear-implant users and hearing-impaired listeners exhibit reduced or absent masking release when large and relatively slow temporal fluctuations are introduced in noise maskers. The multitone maskers used here may provide an effective new diagnostic tool for assessing functional hearing loss and reduced spectral resolution.

Aging as a window into central auditory dysfunction: Combining behavioral and electrophysiological approaches

Central auditory processing involves a complex set of feed-forward and feedback processes governed by a cascade of dynamic neuro-chemical mechanisms. Central auditory dysfunction can arise from disruption of one or more of these processes. With hearing loss, dysfunction may begin with reduced and/or altered input to the central auditory system followed by peripherally induced central plasticity. Similar central changes may occur with advancing age and neurological disorders even in the absence of hearing loss. Understanding the behavioral and physiological consequences of this plasticity on the processing of basic acoustic features is critical for effective clinical management. Major central auditory processing deficits include reduced temporal processing, impaired binaural hearing, and altered coding of spectro-temporal features. These basic deficits are thought to be primary contributing factors to the common complaint of difficulty understanding speech in noisy environments in persons with hearing loss, brain injury, and advanced age. The results of investigations of temporal, spectral, and spectro-temporal processing, binaural hearing, and loudness perception will be presented with a focus on central auditory deficits that occur with advancing age and hearing loss. Such deficits can be tied to reduced peripheral input, altered central coding, and complex changes in cortical representations.

Abstracts fromThe 32nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Abstracts fromThe 32^nd AnnualNational Neurotrauma SymposiumJune 29–July 2, 2014San Francisco, California

Behavioral and neural measures of auditory selective attention in blast-exposed veterans with traumatic brain injury

It is estimated that 15–20% of veterans returning from combat operations have experienced some sort of traumatic brain injury (TBI), a majority of which are the result of exposure to blast forces from military ordinance. Many of these veterans complain of complications when understanding speech in noisy environments, even when they have normal or near normal audiograms. Here, ten veterans diagnosed with mild TBI performed a selective auditory attention task in which they identified the shape of one of three simultaneously occurring ITD-spatialized melodies. TBI subject performance was significantly worse than that of 17 adult controls. Importantly, the veterans had hearing thresholds within 20 dB HL up to 8 kHz and brainstem responses indistinguishable from those of the controls. Cortical response potentials (measured on the scalp using electroencephalography) from correctly identified trials showed weaker attention-related modulation than in controls. These preliminary results suggest blast exposure dama...

Top–down restoration of speech in cochlear-implant users

In noisy listening conditions, intelligibility of degraded speech can be enhanced by top-down restoration. Cochlear implant (CI) users have difficulty understanding speech in noisy environments. This could partially be due to reduced top-down restoration of speech, which may be related to the changes that the electrical stimulation imposes on the bottom-up cues. We tested this hypothesis using the phonemic restoration (PhR) paradigm in which speech interrupted with periodic silent intervals is perceived illusorily continuous (continuity illusion or CoI) and becomes more intelligible (PhR benefit) when the interruptions are filled with noise bursts. Using meaningful sentences, both CoI and PhR benefit were measured in CI users, and compared with those of normal-hearing (NH) listeners presented with normal speech and 8-channel noise-band vocoded speech, acoustically simulating CIs. CI users showed different patterns in both PhR benefit and CoI, compared to NH results with or without the noise-band vocoding. However, they were able to use top-down restoration under certain test conditions. This observation supports the idea that changes in bottom-up cues can impose changes to the top–down processes needed to enhance intelligibility of degraded speech. The knowledge that CI users seem to be able to do restoration under the right circumstances could be exploited in patient rehabilitation and product development.

The role of the medial olivocochlear system in the complaints of understanding speech in noisy environments by individuals with normal hearing

The aim of our study is to investigate the relationship between the complaint of speech understanding in noisy environments and the findings of contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise test methods in individuals with normal hearing. Sixty-nine subjects between 18 and 53 years of age with normal hearing participated in the present study. The subjects were assigned to one of two groups, reported difficulty understanding speech in noise or no reported difficulty understanding speech in noise. After hearing and immitancemetric evaluation, contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise tests were administered to both groups. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.5, 2.0, 3.0 and 4.0kHz. We found out that the speech recognition in noise scores and contralateral suppression values were lower in subjects with the complaint of speech understanding in noise than those who do not have such complaints. We concluded that the complaint of speech understanding in noise may be related to the medial efferent system dysfunction, so central auditory nervous system.

Estéreos pessoais: hábitos auditivos e avaliação audiológica

OBJETIVO: Caracterizar os hábitos auditivos e relacioná-los aos achados audiológicos de adultos sem queixas auditivas, usuários de estéreos pessoais. MÉTODOS: Foram avaliados 85 indivíduos, com idades entre 18 e 34 anos, com audição normal, sem exposição a ruído ocupacional. Todos responderam a um questionário de hábitos auditivos, disponibilizado na Internet e foram convocados para a avaliação audiológica: Audiometria Altas Frequências, Emissões Otoacústicas Evocadas por Estímulo Transiente (EOAT) e Emissões Otoacústicas Evocadas por Produto de Distorção (EOAPD). RESULTADOS: Os participantes do estudo ficam expostos à música por mais de duas horas diárias, há mais de quatro anos, normalmente em meios de transporte. Observou-se um entalhe em 6 kHz no delineamento da configuração audiométrica a partir das médias dos limiares auditivos de via aérea, característico de PAIR. Quanto maior o tempo (em anos) de exposição ao som, maior a chance de ausência de EOAT e incidência de zumbido. A maioria se preocupa com a saúde auditiva e acredita que os maus hábitos podem causar danos à audição. CONCLUSÃO: Embora os indivíduos não tenham apresentado queixas auditivas, aspectos relacionados à exposição ao ruído foram evidenciados, tais como zumbido, estresse e relatos de dificuldade crescente de inteligibilidade de fala com o aumento do ruído ambiental.

Effect of degraded binaural cues in cochlear implant users and normal hearing listeners on spatial release from masking

Bilateral cochlear implants (BiCIs) are being provided to a growing number of individuals with bilateral severe-profound hearing loss and are becoming standard in many clinics worldwide, to restore spatial hearing skills and improve speech understanding in noisy environments. While patients generally perform better with BiCIs, their performance is significantly worse than that of normal hearing (NH) listeners. Spatial release from masking (SRM) in NH listeners depends on monaural (head shadow) and binaural cues. In BiCI users, SRM appears to be primarily due to head shadow; however, binaural-mediated SRM is weak or absent. Two factors are most likely responsible for this. First, bilateral CI processors are not coordinated, rendering binaural cues weak, absent or inconsistent. Second, patients' history with auditory deprivation likely results in poor neural survival at numerous cochlear locations. Our studies suggest that signal processing tools can be applied to bilateral CI users to restore binaural sensitivity. In this talk, data will be presented from studies with adults and children, in free field and using binaural research processors. Results from studies on restoration of interaural level and timing differences to BiCI users will be discussed in the context of what is needed for binaural SRM restoration. Work supported by NIH-NIDCD (grants 5R01DC003083 and 5R01DC8365)

Development and Evaluation of the LiSN & Learn Auditory Training Software for Deficit-Specific Remediation of Binaural Processing Deficits in Children: Preliminary Findings

The LiSN & Learn auditory training software was developed specifically to improve binaural processing skills in children with suspected central auditory processing disorder who were diagnosed as having a spatial processing disorder (SPD). SPD is defined here as a condition whereby individuals are deficient in their ability to use binaural cues to selectively attend to sounds arriving from one direction while simultaneously suppressing sounds arriving from another. As a result, children with SPD have difficulty understanding speech in noisy environments, such as in the classroom. To develop and evaluate the LiSN & Learn auditory training software for children diagnosed with the Listening in Spatialized Noise-Sentences Test (LiSN-S) as having an SPD. The LiSN-S is an adaptive speech-in-noise test designed to differentially diagnose spatial and pitch-processing deficits in children with suspected central auditory processing disorder. Participants were nine children (aged between 6 yr, 9 mo, and 11 yr, 4 mo) who performed outside normal limits on the LiSN-S. In a pre-post study of treatment outcomes, participants trained on the LiSN & Learn for 15 min per day for 12 weeks. Participants acted as their own control. Participants were assessed on the LiSN-S, as well as tests of attention and memory and a self-report questionnaire of listening ability. Performance on all tasks was reassessed after 3 mo where no further training occurred. The LiSN & Learn produces a three-dimensional auditory environment under headphones on the user's home computer. The child's task was to identify a word from a target sentence presented in background noise. A weighted up-down adaptive procedure was used to adjust the signal level of the target based on the participant's response. On average, speech reception thresholds on the LiSN & Learn improved by 10 dB over the course of training. As hypothesized, there were significant improvements in posttraining performance on the LiSN-S conditions where the target and distracter stimuli are spatially separated and which specifically evaluate binaural processing ability (p ranging from <.003 to .0001, η2 ranging from 0.694 to 0.873). In contrast, there was no improvement on the LiSN-S control conditions where the target and distracter stimuli emanate from the same direction (p ranging from .07 to .86, η2 ranging from 0.362 to 0.004). Significant improvements were found posttraining on measures of memory, on one measure of attention, and on self-reported ratings of listening ability. There were no significant differences between post- and 3 mo posttraining scores on any of the assessment tools. The initial LiSN & Learn study has shown that children as young as 6 yr of age are able to complete the training (although some coaxing was needed in a minority of cases). Both parents and children have reported benefits from the training, and feedback from the trial has resulted in extra features being added to the software. In order to further evaluate the efficacy of LiSN & Learn to remediate binaural processing deficits in children a clinical trial is currently under way utilizing a randomized blinded control group design.

Auditory-cognitive interactions underlying interaural asymmetry in an adult listener: A case study

Objective: Abnormal interaural asymmetry on tests of dichotic listening is commonly observed in individuals suspected of auditory processing disorder (APD). Although a structural basis for the abnormality has been widely accepted, the influence of cognitive variables on the degree of observed asymmetry has gained increasing attention. To study this issue, we manipulated cognitive influences on interaural asymmetry in an adult with the auditory complaints typically associated with APD. Study sample: A 55 year-old woman with complaints of difficulty understanding speech in noisy environments despite normal audiometric levels. Design: Several experimental dichotic procedures were administered. Each procedure was characterized by the manipulation of cognitive task demands. Results: Interaural asymmetry was greatest when the demands on attention and/or memory were maximal. Electrophysiological data revealed interaural asymmetry on later stages of information processing. Conclusions: Results are discussed in relation to auditory-specific outcomes on clinical tests for APD.

Evaluation of noise reduction technologies in a contemporary cochlear implant system

Evaluation of noise reduction technologies in a contemporary cochlear implant system

Bilateral cochlear implants in young children.

Cochlear implants (CIs) are provided to a growing number of people who are deaf. Single CIs offer opportunity for language acquisition, but there exist remaining challenges. In normal‐hearing individuals binaural hearing provides cues that are important for sound localization and speech understanding in noisy environments. Provision of bilateral CIs to many children occurs with the expectation that they will develop spatial hearing abilities. Outcomes in these children are mixed; while some are able to localize sound significantly better with bilateral CIs than with a single CI, other children demonstrate poor spatial hearing skills. Factors that seem to contribute to performance include amount of auditory deprivation prior to implantation and auditory experience following bilateral activation. Hardware/software limitations in implanted devices result in binaural cues being distorted or discarded. Studies using research processors show that these cues can be transmitted with fidelity to the patients, but that perceptual sensitivity to these cues may depend on the period of auditory deprivation that listeners have experienced. This talk will focus on progress and outcomes in children who are deaf and use bilateral CIs, with suggestions for future development that will depend on improved audio signal processing and signal delivery to the implantable devices.

Formal auditory training in adult hearing aid users

INTRODUCTIONIndividuals with sensorineural hearing loss are often able to regain some lost auditory function with the help of hearing aids. However, hearing aids are not able to overcome auditory distortions such as impaired frequency resolution and speech understanding in noisy environments. The coexistence of peripheral hearing loss and a central auditory deficit may contribute to patient dissatisfaction with amplification, even when audiological tests indicate nearly normal hearing thresholds.OBJECTIVEThis study was designed to validate the effects of a formal auditory training program in adult hearing aid users with mild to moderate sensorineural hearing loss.METHODSFourteen bilateral hearing aid users were divided into two groups: seven who received auditory training and seven who did not. The training program was designed to improve auditory closure, figure-to-ground for verbal and nonverbal sounds and temporal processing (frequency and duration of sounds). Pre- and post-training evaluations included measuring electrophysiological and behavioral auditory processing and administration of the Abbreviated Profile of Hearing Aid Benefit (APHAB) self-report scale.RESULTSThe post-training evaluation of the experimental group demonstrated a statistically significant reduction in P3 latency, improved performance in some of the behavioral auditory processing tests and higher hearing aid benefit in noisy situations (p-value < 0,05). No changes were noted for the control group (p-value <0,05).CONCLUSIONThe results demonstrated that auditory training in adult hearing aid users can lead to a reduction in P3 latency, improvements in sound localization, memory for nonverbal sounds in sequence, auditory closure, figure-to-ground for verbal sounds and greater benefits in reverberant and noisy environments.

The Benefits of Remote Microphone Technology for Adults with Cochlear Implants

Cochlear implantation has become a standard practice for adults with severe to profound hearing loss who demonstrate limited benefit from hearing aids. Despite the substantial auditory benefits provided by cochlear implants, many adults experience difficulty understanding speech in noisy environments and in other challenging listening conditions such as television. Remote microphone technology may provide some benefit in these situations; however, little is known about whether these systems are effective in improving speech understanding in difficult acoustic environments for this population. This study was undertaken with adult cochlear implant recipients to assess the potential benefits of remote microphone technology. The objectives were to examine the measurable and perceived benefit of remote microphone devices during television viewing and to assess the benefits of a frequency-modulated system for speech understanding in noise. Fifteen adult unilateral cochlear implant users were fit with remote microphone devices in a clinical environment. The study used a combination of direct measurements and patient perceptions to assess speech understanding with and without remote microphone technology. The direct measures involved a within-subject repeated-measures design. Direct measures of patients' speech understanding during television viewing were collected using their cochlear implant alone and with their implant device coupled to an assistive listening device. Questionnaires were administered to document patients' perceptions of benefits during the television-listening tasks. Speech recognition tests of open-set sentences in noise with and without remote microphone technology were also administered. Participants showed improved speech understanding for television listening when using remote microphone devices coupled to their cochlear implant compared with a cochlear implant alone. This benefit was documented both when listening to news and talk show recordings. Questionnaire results also showed statistically significant differences between listening with a cochlear implant alone and listening with a remote microphone device. Participants judged that remote microphone technology provided them with better comprehension, more confidence, and greater ease of listening. Use of a frequency-modulated system coupled to a cochlear implant also showed significant improvement over a cochlear implant alone for open-set sentence recognition in +10 and +5 dB signal to noise ratios. Benefits were measured during remote microphone use in focused-listening situations in a clinical setting, for both television viewing and speech understanding in noise in the audiometric sound suite. The results suggest that adult cochlear implant users should be counseled regarding the potential for enhanced speech understanding in difficult listening environments through the use of remote microphone technology.

Untersuchungen zum Einfluss des Mischungsverhältnisses der FM-Anlage auf das Sprachverständnis im Störschall bei CI-Patienten

At school we find two major acoustic situations: (first) the "teacher is talking" being disturbed by the pupils making noise and (second) another "pupil is talking" disturbed by other pupils. The understanding of words and sentences in hearing impaired patients with a cochlear implant (CI) in a noisy situation can be improved by using a FM system. The aim of this study is to test speech understanding depending on mixing ratios between FM input and microphone input to the speech processor in different circumstances. Speech understanding was evaluated using the adaptive Oldenburger sentence test (OLSA) in background noise. CI patients used the FM system Microlink for Freedom CIs together with a Campus transmitter (Phonak AG). 17 postlingually deafened adults were tested, using unilateral Freedom cochlear implant systems (Cochlear Ltd). A group of eight normally hearing adults was used as a control group in the same setup. We found that the median value of L (50)=1.6 dB in CI patients without a FM system is higher than the median value of L(50)=-13 dB in normally hearing subjects. The sentence recognition in CI patients with FM system increased with increasing mixing ratio. The benefit using the FM system to understand the teacher is of high advantage in any mixing ratio. The difference between the L(50) values in situations with or without a FM-system is 15 dB for the mixing ratio 3:1 (FM to microphone). If we take into account an increase of 15% per dB in the OLSA (at L(50)) in CI patients, the difference of 15 dB means a calculated advantage of 225%. The speech understanding during the second condition ("pupil is talking") however remained nearly the same in all used mixing ratios. The calculations showed no statistical difference between these situations with and without a FM system. The speaker comprehension for the two investigated listening conditions showed different results. Understanding in the "teacher is talking" situation increased with increasing mixing ratio (FM to microphone) and in the "pupil is talking" situation remained on the same level. We could not find an optimal FM setting for both listening conditions. This leads to different suggestions for different listening conditions. All patients showed an increased speech understanding in noisy environments. This result strongly encourages the use of a FM-system in a classroom.

Music perception in cochlear implant users and its relationship with psychophysical capabilities

This article describes issues concerning music perception with cochlear implants, discusses why music perception is usually poor in cochlear implant users, reviews relevant data, and describes approaches for improving music perception with cochlear implants. Pitch discrimination ability ranges from the ability to hear a one-semitone difference to a two-octave difference. The ability to hear rhythm and tone duration is near normal in implantees. Timbre perception is usually poor, but about two-thirds of listeners can identify instruments in a closed set better than chance. Cochlear implant recipients typically have poor melody perception but are aided with rhythm and lyrics. Without rhythm or lyrics, only about one-third of implantees can identify common melodies in a closed set better than chance. Correlations have been found between music perception ability and speech understanding in noisy environments. Thus, improving music perception might also provide broader clinical benefit. A number of approaches have been proposed to improve music perception with implant users, including encoding fundamental frequency with modulation, "current-steering," MP3-like processing, and nerve "conditioning." If successful, these approaches could improve the quality of life for implantees by improving communication and musical and environmental awareness.

From the editor: special issue on auditory scene analysis.

The most common complaint of a person with hearing loss is difficulty in understanding speech in noisy environments. Although communicating in noisy environments can prove challenging to people with normal hearing, the brain uses acoustic cues from a complex sound mixture to separate the speech signal of interest from competing sounds, a process known as auditory scene analysis. In a cocktail party, we can thus identify and concentrate on the speech of the person with whom we are speaking from the competing speech of other talkers, or follow a conversation among multiple talkers when seated at a table in a noisy restaurant. Although it has long been known that people with hearing loss have greater difficulty decoding speech in noisy situations (with or without hearing aids), little was known about how hearing loss or how the signal processing in hearing prostheses (hearing aids or cochlear implants) might affect specific aspects of listening thought to be important to auditory scene analysis. This issue of Trends in Amplification contains a series of articles that focus on aspects of listening in complex environments by persons with hearing loss, the effect of hearing aids and cochlear implants on listener performance in difficult listening environments, and how information about the mechanisms underlying auditory scene analysis might be used to improve the design of hearing aids and cochlear implants. In the first article, Shinn-Cunningham and Best focus on the role of selective attention in complex listening situations, that is, the “cocktail party” problem. They provide a description and explanation of why and how listeners with normal hearing are able to use attention to separate the wanted signal from a mixture of multiple voices, and they explain how the degradation of “bottom-up” cues because of hearing loss might affect auditory object formation and the ability to use selective attention. Finally, the authors address how hearing aids might help or hinder listening in complex listening environments. In the second article, Marrone, Mason, and Kidd report the results of a study investigating the ability of hearing aid users to benefit from spatial separation of the target talker and competing talkers (spatial release from masking) in reverberant environments. Listeners with hearing loss were tested with and without their personal hearing aids (unilateral and bilateral test conditions). Age-matched listeners with normal hearing served as a control group. The study revealed that listeners with hearing loss did obtain benefit from spatial separation of the target and maskers, but the spatial release from masking was less than that obtained by listeners with normal hearing. Greater benefit was obtained in the bilateral listening condition. The third article, by Oxenham, focuses on the role of pitch in grouping sounds from the same source and segregating sounds from different sources when listening in complex environments. The article provides a tutorial on current models of pitch perception, as well as a review of research on pitch perception and pitch and sound source segregation by listeners with normal hearing and hearing loss. The importance of preserving spectral information and temporal fine structure in hearing aid and cochlear implant processors is emphasized. In the final article, Wang describes an engineering approach to the problem of separating signal from noise. Wang introduces the idea of using time-frequency masks for the purpose of separating speech from interfering noise and also reviews recent research in this area. The suitability of this approach for hearing aid applications is discussed.

A Two-Microphone Noise Reduction System for Cochlear Implant Users with Nearby Microphones—Part I: Signal Processing Algorithm Design and Development

Users of cochlear implant systems, that is, of auditory aids which stimulate the auditory nerve at the cochlea electrically, often complain about poor speech understanding in noisy environments. Despite the proven advantages of multimicrophone directional noise reduction systems for conventional hearing aids, only one major manufacturer has so far implemented such a system in a product, presumably because of the added power consumption and size. We present a physically small (intermicrophone distance 7 mm) and computationally inexpensive adaptive noise reduction system suitable for behind-the-ear cochlear implant speech processors. Supporting algorithms, which allow the adjustment of the opening angle and the maximum noise suppression, are proposed and evaluated. A portable real-time device for test in real acoustic environments is presented.

A two-stage binaural speech enhancement approach for hearing aids with preserving binaural benefits in noisy environments

Speech enhancement is one of the most crucial functions, if not the most, in hearing aids, as hearing impaired people have great difficulty in understanding speech in noisy environments. In this paper, we propose a two-stage binaural speech enhancement approach for hearing aids, which consists of interference estimation by pre-trained adaptive filters and speech enhancement using the Wiener filters. Main attention is then paid to the theoretical analysis of this system and the experimental comparisons with the traditional binaural speech enhancement approaches. The comparisons are conducted with the following two considerations: interference suppression performance and the ability in preserving binaural cues which give birth to listener's own “binaural gain.” We finally give the general discussion on this proposed binaural speech enhancement algorithm from the viewpoints of theory, through implementation, to evaluation.

Central Auditory Processing (CAP) Abnormalities in Older Adults: A Review

Older adults, with and without measured hearing loss, often report difficulties in following rapid speech and difficulties in understanding speech in noisy environments. It is likely that these difficulties arise from: (a) deteriorating peripheral hearing and/or (b) structural changes to the central auditory system (CAS) and/or (c) changes to normal cognitive function. This review will focus on the structural changes to the CAS and the likely central auditory processing (CAP) abnormality arising from these changes. Older, compared with young normal hearing adults, show physiological and behavioural differences on measures of sound localisation, and in the detection of small and/or rapid changes to the temporal properties of various auditory stimuli. This article will review these differences together with prevalence and risk factors for CAP abnormality in older adults. The impact of this condition on the older adult as well as potential approaches to rehabilitation and (re)training will also be reviewed.