Speech In Background Noise Research Articles

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The benefits of bilateral and directionally selective auditory prostheses

Both binaural hearing and directional microphones can improve understanding of speech in background noise if the sources of the speech and noise are spatially separated. We used a model of spatial release from masking [Jelfs, et al. (2011). Hear Res. 275, 96-104.] to predict the benefits of bilateral prostheses, directional microphones and head orientation. The model predicts large benefits of each of these factors. Measurements using selected spatial configurations in both normally hearing listeners and unilateral cochlear implantees confirmed the model's predictions. The reception thresholds for bilateral implantees were inferred using mirror-image spatial configurations to be at least 18 dB better than unilateral implantees in certain situations. Expected effects of directional microphones and head orientation were assessed through modelling spatial release from masking in a virtual restaurant situation. The model predicted marked differences between different seating positions, but in most locations, both moderate head rotations and directional microphones offered substantial benefits. Use of directional microphones generally offered larger benefits than head rotation, but there was little benefit from their combination. The addition of reverberation elevated predicted thresholds and reduced all of these effects.

Talker-identification training using simulations of binaurally combined electric and acoustic hearing: Generalization to speech and emotion recognition

Understanding speech in background noise, talker identification, and vocal emotion recognition are challenging for cochlear implant (CI) users due to poor spectral resolution and limited pitch cues with the CI. Recent studies have shown that bimodal CI users, that is, those CI users who wear a hearing aid (HA) in their non-implanted ear, receive benefit for understanding speech both in quiet and in noise. This study compared the efficacy of talker-identification training in two groups of young normal-hearing adults, listening to either acoustic simulations of unilateral CI or bimodal (CI+HA) hearing. Training resulted in improved identification of talkers for both groups with better overall performance for simulated bimodal hearing. Generalization of learning to sentence and emotion recognition also was assessed in both subject groups. Sentence recognition in quiet and in noise improved for both groups, no matter if the talkers had been heard during training or not. Generalization to improvements in emotion recognition for two unfamiliar talkers also was noted for both groups with the simulated bimodal-hearing group showing better overall emotion-recognition performance. Improvements in sentence recognition were retained a month after training in both groups. These results have potential implications for aural rehabilitation of conventional and bimodal CI users.

Noise reduction for auditory prostheses based on harmonic detection

Difficulty in understanding speech in background noise is one of the most common complaints of hearing-aid and cochlear-implant users. Various noise-reduction and spectral-enhancement algorithms have been designed and tested over the years, often with limited success in terms of improving speech intelligibility. A commonly used method involves spectral subtraction, which is based on the assumption that the noise spectrum can be estimated and the clean speech signal can be extracted by subtracting the noise spectrum from the noisy speech signal. However, recent studies have shown that such methods often result in poorer signal-to-noise ratios in the modulation-spectrum domain, which may explain why little benefit in speech intelligibility has been found. Also, identifying noise in terms of its stationarity runs the risk of misidentification in more stationary signals, such as music. Here a noise reduction algorithm based on harmonic detection and enhancement was explored. Simulation results showed that this algorithm could help suppress noise in both speech and music. Results from perceptual tests will be reported. [Supported in part by Advanced Bionics.]

Playing Music for a Smarter Ear: Cognitive, Perceptual and Neurobiological Evidence.

Human hearing depends on a combination of cognitive and sensory processes that function by means of an interactive circuitry of bottom-up and top-down neural pathways, extending from the cochlea to the cortex and back again. Given that similar neural pathways are recruited to process sounds related to both music and language, it is not surprising that the auditory expertise gained over years of consistent music practice fine-tunes the human auditory system in a comprehensive fashion, strengthening neurobiological and cognitive underpinnings of both music and speech processing. In this review we argue not only that common neural mechanisms for speech and music exist, but that experience in music leads to enhancements in sensory and cognitive contributors to speech processing. Of specific interest is the potential for music training to bolster neural mechanisms that undergird language-related skills, such as reading and hearing speech in background noise, which are critical to academic progress, emotional health, and vocational success.

A neural basis of speech-in-noise perception in older adults.

We investigated a neural basis of speech-in-noise perception in older adults. Hearing loss, the third most common chronic condition in older adults, is most often manifested by difficulty understanding speech in background noise. This trouble with understanding speech in noise, which occurs even in individuals who have normal-hearing thresholds, may arise, in part, from age-related declines in central auditory processing of the temporal and spectral components of speech. We hypothesized that older adults with poorer speech-in-noise (SIN) perception demonstrate impairments in the subcortical representation of speech. In all participants (28 adults, age 60-73 yr), average hearing thresholds calculated from 500 to 4000 Hz were ≤ 25 dB HL. The participants were evaluated behaviorally with the Hearing in Noise Test (HINT) and neurophysiologically using speech-evoked auditory brainstem responses recorded in quiet and in background noise. The participants were divided based on their HINT scores into top and bottom performing groups that were matched for audiometric thresholds and intelligent quotient. We compared brainstem responses in the two groups, specifically, the average spectral magnitudes of the neural response and the degree to which background noise affected response morphology. In the quiet condition, the bottom SIN group had reduced neural representation of the fundamental frequency of the speech stimulus and an overall reduction in response magnitude. In the noise condition, the bottom SIN group demonstrated greater disruption in noise, reflecting reduction in neural synchrony. The role of brainstem timing is particularly evident in the strong relationship between SIN perception and quiet-to-noise response correlations. All physiologic measures correlated with SIN perception. Adults in the bottom SIN group differed from the audiometrically matched top SIN group in how speech was neurally encoded. The strength of subcortical encoding of the fundamental frequency appears to be a factor in successful speech-in-noise perception in older adults. Given the limitations of amplification, our results suggest the need for inclusion of auditory training to strengthen central auditory processing in older adults with SIN perception difficulties.

Problems Hearing in Noise in Older Adults

Difficulty understanding speech in background noise, even with amplification to restore audibility, is a common problem for hearing-impaired individuals and is especially frequent in older adults. Despite the debilitating nature of the problem the cause is not yet completely clear. This review considers the role of spatial processing ability in understanding speech in noise, highlights the potential impact of disordered spatial processing, and attempts to establish if aging leads to reduced spatial processing ability. Evidence supporting and opposing the hypothesis that spatial processing is disordered among the aging population is presented. With a few notable exceptions, spatial processing ability was shown to be reduced in an older population in comparison to young adults, leading to poorer speech understanding in noise. However, it is argued that to conclude aging negatively effects spatial processing ability may be oversimplified or even premature given potentially confounding factors such as cognitive ability and hearing impairment. Further research is required to determine the effect of aging and hearing impairment on spatial processing and to investigate possible remediation options for spatial processing disorder.

Age-Related Changes in Listening Effort for Various Types of Masker Noises

The purpose of the present study was to evaluate the relationship between cognitive function, listening effort, and speech recognition for a group of younger and older adults with normal hearing and a group of older adults with hearing impairment in various types of background maskers. The authors hypothesize that, as the masker condition becomes more difficult listening effort will increase, but the increase will be greater for older participants than for younger participants. A dual-task paradigm was used to objectively evaluate listening effort. The primary task required participants to repeat sentences presented in three different background-masker conditions: (1) two-talker (TT), (2) six-talker, and (3) speech-shaped noise (SSN). The secondary task was a Digital Visual Pursuit Rotor Tracking test, for which participants were instructed to use a computer mouse to track a moving target around an ellipse that was displayed on a computer screen. Each of the two tasks was separately and concurrently presented at a fixed overall speech-recognition performance level of 76% correct. In addition, participants subjectively rated how easy it was to listen to the sentences in each masker condition on a scale from 0 (i.e., very difficult) to 100 (i.e., very easy). Last, participants completed a battery of cognitive tests that measured working memory (Reading Span Test), processing speed (Digit Symbol Substitution Test), and selective attention (Stroop Test) ability. Results revealed that participants' working memory and processing speed abilities were significantly related to their speech-recognition performance in noise in all three background-masker conditions. Participants rated the TT condition to be the most difficult listening condition and the SSN condition to be the easiest listening condition. Both groups of older participants expended significantly more listening effort than younger participants did in the SSN and TT masker conditions. For each group of participants, there were no significant differences in listening effort measured across the masker conditions, with the exception of the younger participants, who expended more effort listening in the six-talker masker condition compared with the SSN condition. Participants' listening effort expended on the TT and SSN masker conditions was significantly correlated with their working memory and processing speed performance. Findings from the present study indicate that older adults require more cognitive resources than younger adults to understand speech in background noise.

Can You Hear Me Now? Musical Training Shapes Functional Brain Networks for Selective Auditory Attention and Hearing Speech in Noise

Even in the quietest of rooms, our senses are perpetually inundated by a barrage of sounds, requiring the auditory system to adapt to a variety of listening conditions in order to extract signals of interest (e.g., one speaker's voice amidst others). Brain networks that promote selective attention are thought to sharpen the neural encoding of a target signal, suppressing competing sounds and enhancing perceptual performance. Here, we ask: does musical training benefit cortical mechanisms that underlie selective attention to speech? To answer this question, we assessed the impact of selective auditory attention on cortical auditory-evoked response variability in musicians and non-musicians. Outcomes indicate strengthened brain networks for selective auditory attention in musicians in that musicians but not non-musicians demonstrate decreased prefrontal response variability with auditory attention. Results are interpreted in the context of previous work documenting perceptual and subcortical advantages in musicians for the hearing and neural encoding of speech in background noise. Musicians’ neural proficiency for selectively engaging and sustaining auditory attention to language indicates a potential benefit of music for auditory training. Given the importance of auditory attention for the development and maintenance of language-related skills, musical training may aid in the prevention, habilitation, and remediation of individuals with a wide range of attention-based language, listening and learning impairments.

Effects of Word Recognition Score as a Function of Auditory Training Terms for Elderly Hearing Impaired with Hearing Aid

Although a use of hearing aids improves speech audibility, it is known that elderly hearing-impaired listeners often exhibit difficulty understanding speech in background noise. The purpose of this study was to examine a short-term (8-week) auditory training in word-recognition performance of 24 old hearing aid users. Twelve aged listeners (M=76.2 yrs) participated as auditory training group (ATG), and other twelve old listeners (M=74.0 yrs) served as non-training group (NTG). The ATG received forty-minute auditory training twice a week across the entire 8 weeks of training. During the training, the target monosyllabic words (Korean monosyllabic words) were presented in both open-set and closed-set aided conditions. All the words were presented at the most comfortable level of each participant with four different signal-to-noise ratios (SNRs of -5, 0, +5, +10 dB). To check the training benefit, word-recognition performance of ATG was tested after 1-, 4-, 8-week trainings. Results showed that word recognition performance of NTG did not improve as expected. Word recognition score of ATG was, however, significantly increased after 8-week training. Even though 4-week training results revealed a tendency of increment in word-recognition performance, a positive change after 4-week training was not significant. The amount of improvement after 8-week auditory training was the greatest at +10 dB SNR and the least at -5 dB SNR. The results indicate that the short-term (8-week) auditory training would be beneficial for old listeners to recognize speech in the background noise yet the training effect would depend on the SNRs. Therefore, at least 8 weeks of training in various listening conditions should be considered for elderly hearing aid users who want training benefit in daily listening and communication. KEY WORDS：Auditory training·Elderly hearing impaired·Hearing aid·Signal-to-noise (SNR)·Word recognition score.

Impact of Hair Cell Preservation in Cochlear Implantation

This article reviews some of the potential benefits of preserving low-frequency residual hearing using a short-electrode cochlear implant. Both the status of the inner ear and acoustic characteristics of speech cues are important factors. How does the magnitude of the potential benefits depend on the candidacy criteria for implantation with a hearing-preservation electrode? Previous research has demonstrated that preserving residual hearing in cochlear implantation can provide significant advantages for the understanding of speech in background noise as well as for the aesthetic qualities of music and other sounds. Developing optimal candidacy guidelines for these devices is a current goal. In a large group of patients with Hybrid (acoustic + electric) cochlear implant, performance in the recognition of speech in background of other talkers is measured and compared with patients with traditional long-electrode implant. In addition, a number of patient characteristics are compared to success with the short-electrode implant. Age and duration of hearing loss are found to be predictive factors for the success of the short-electrode approach. Optimal criterion for candidacy for the use of the short-electrode versus a traditional long electrode can improve the outlook for patients with severe-to-profound high-frequency hearing loss.

Neural Timing Is Linked to Speech Perception in Noise

Understanding speech in background noise is challenging for every listener, including those with normal peripheral hearing. This difficulty is attributable in part to the disruptive effects of noise on neural synchrony, resulting in degraded representation of speech at cortical and subcortical levels as reflected by electrophysiological responses. These problems are especially pronounced in clinical populations such as children with learning impairments. Given the established effects of noise on evoked responses, we hypothesized that listening-in-noise problems are associated with degraded processing of timing information at the brainstem level. Participants (66 children; ages, 8-14 years; 22 females) were divided into groups based on their performance on clinical measures of speech-in-noise (SIN) perception and reading. We compared brainstem responses to speech syllables between top and bottom SIN and reading groups in the presence and absence of competing multitalker babble. In the quiet condition, neural response timing was equivalent between groups. In noise, however, the bottom groups exhibited greater neural delays relative to the top groups. Group-specific timing delays occurred exclusively in response to the noise-vulnerable formant transition, not to the more perceptually robust, steady-state portion of the stimulus. These results demonstrate that neural timing is disrupted by background noise and that greater disruptions are associated with the inability to perceive speech in challenging listening conditions.

F1 (CBA×C57) mice show superior hearing in old age relative to their parental strains: Hybrid vigor or a new animal model for “Golden Ears”?

Age-related hearing loss - presbycusis - is the most common communication problem and third most prevalent chronic medical disorder of the aged. The CBA and C57BL/6 mouse strains are useful for studying features of presbycusis. The CBA loses its hearing slowly, like most humans. Because the C57 develops a rapid, high frequency hearing loss by middle age, it has an "old" ear but a relatively young brain, a model that helps separate peripheral (cochlear) from central (brain) etiologies. This field of sensory neuroscience lacks a good mouse model for the 5-10% of aged humans with normal cochlear sensitivity, but who have trouble perceiving speech in background noise. We hypothesized that F1 (CBA×C57) hybrids would have better hearing than either parental strain. Measurements of peripheral auditory sensitivity supported this hypothesis, however, a rapid decline in the auditory efferent feedback system, did not. Therefore, F1s might be an optimal model for studying cases where the peripheral hearing is quite good in old age; thereby allowing isolation of central auditory changes due to brain neurodegeneration.

Sequential stream segregation using temporal periodicity cues in cochlear implant recipients

Sequential stream segregation involves the ability of a listener to perceptually segregate two rapidly alternating sounds into different perceptual streams. By studying auditory streaming in cochlear implants (CIs), one can obtain a better understanding of the cues that CI recipients can use to segregate different sound sources, which may have relevance to such everyday activities as the understanding of speech in background noise. This study focuses on the ability of CI users to use temporal periodicity cues to perform auditory stream segregation. A rhythmic discrimination task involving sequences of alternating amplitude-modulated (AM) noises is used. The results suggest that most CI users can stream AM noise bursts at relatively low modulation frequencies (near 80 Hz AM), but that this ability diminishes at higher modulation frequencies. Additionally, the ability of CI users to perform streaming using temporal periodicity cues appears to be comparable to that of normal-hearing listeners. These results imply that CI subjects may in certain contexts (i.e., when the talker has a low fundamental frequency voice) be able to use temporal periodicity cues to segregate and thus understand the voices of competing talkers.

Music and Cochlear Implants

Music and Cochlear Implants

Reflections on 40 Years of Amplification

Reflections on 40 Years of Amplification

Rehabilitative Management Strategies in Patients With King-Kopetzky Syndrome

King-Kopetzky syndrome (KKS) is defined as the condition in which an individual complains of difficulties understanding speech in background noise, but has normal thresholds on pure tone audiometry. Various studies have claimed that a number of factors, including peripheral and central auditory function, linguistic, speech processes and psychological factors, may be responsible for the condition. Because of the large variety of the causes underlying this condition, the clinical management of such a multifactorial disorder is extremely diverse. The purpose of this article is to highlight important aspects of the appropriate rehabilitative management strategies that should be considered in audiology clinics to treat this unique population of patients, and provide guidelines leading towards their effective rehabilitative management.

Selecting Speech Tests to Measure Auditory Function

Selecting Speech Tests to Measure Auditory Function

Binaural function and its benefits for wearers of hearing aids

Hearing-aid design has been predicated traditionally on improving the reception of speech in background noise, a goal that has, at least in part, been successfully attained. Despite the advances, hearing-aid wearers continue to have difficulty in complex acoustic environments and in auditory tasks where normal-hearing listeners benefit greatly from binaural hearing. In order to improve hearing-aid wearers' performance in such challenging conditions, recent research has begun examining the effects of hearing aids on binaural perception. Interest in the topic is heightened by the rapidly approaching prospect of bilateral hearing aids that communicate wirelessly and thereby allow implementation of more complex signal-processing algorithms than currently possible. This talk will review binaural function and its benefits, with particular emphasis on the aspects that hearing aids can affect. The talk will also speculate on which hearing-aid algorithms can affect binaural perception.

Ageing without hearing loss or cognitive impairment causes a decrease in speech intelligibility only in informational maskers

In most everyday settings, speech is heard in the presence of competing sounds and understanding speech requires skills in auditory streaming and segregation, followed by identification and recognition, of the attended signals. Ageing leads to difficulties in understanding speech in noisy backgrounds. In addition to age-related changes in hearing-related factors, cognitive factors also play a role but it is unclear to what extent these are generalized or modality-specific cognitive factors. We examined how ageing in normal-hearing decade age cohorts from 20 to 69 years affected discrimination of open-set speech in background noise. We used two types of sentences of similar structural and linguistic characteristics but different masking levels (i.e. differences in signal-to-noise ratios required for detection of sentences in a standard masker) so as to vary sentence demand, and two background maskers (one causing purely energetic masking effects and the other causing energetic and informational masking) to vary load conditions. There was a decline in performance (measured as speech reception thresholds for perception of sentences in noise) in the oldest cohort for both types of sentences, but only in the presence of the more demanding informational masker. We interpret these results to indicate a modality-specific decline in cognitive processing, likely a decrease in the ability to use acoustic and phonetic cues efficiently to segregate speech from background noise, in subjects aged >60.