Perception In Noisy Environments Research Articles

The impact of tinnitus on speech perception in noise: a systematic review and meta-analysis.

Tinnitus is a condition that causes people to hear sounds without an external source. One significant issue arising from this condition is the difficulty in communicating, especially in the presence of noisy backgrounds. The process of understanding speech in challenging situations requires both cognitive and auditory abilities. Since tinnitus presents unique challenges, it is important to investigate how it affects speech perception in noise. In this review, 32 articles were investigated to determine the effect of tinnitus on the effect of speech in noise perception performance. Based on the meta-analysis performed using a random-effects model, meta-regression was used to explore the moderating effects of age and hearing acuity. A total of 32 studies were reviewed, and the results of the meta-analysis revealed that tinnitus significantly impacts speech in terms of noise perception performance. Additionally, the regression analysis revealed that age and hearing acuity are not significant predictors of speech in noise perception. Our findings suggest that tinnitus affects speech perception in noisy environments due to cognitive impairments and central auditory processing deficits. Hearing loss and aging also contribute to reduced speech in noise performance. Interventions and further research are necessary to address individual challenges associated with continuous subjective tinnitus.

Lexical tone recognition in multi-talker babbles and steady-state noise by Mandarin-speaking children with unilateral cochlear implants or bimodal hearing

Background and objectivesLexical tone presents challenges to cochlear implant (CI) users especially in noise conditions. Bimodal hearing utilizes residual acoustic hearing in the contralateral side and may offer benefits for tone recognition in noise. The purpose of the present study was to evaluate tone recognition in both steady-state noise and multi-talker babbles by the prelingually-deafened, Mandarin-speaking children with unilateral CIs or bimodal hearing. MethodsFifty-three prelingually-deafened, Mandarin-speaking children who received CIs participated in this study. Twenty-two of them were unilateral CI users and 31 wore a hearing aid (HA) in the contralateral ear (i.e., bimodal hearing). All subjects were tested for Mandarin tone recognition in quiet and in two types of maskers: speech-spectrum-shaped noise (SSN) and two-talker babbles (TTB) at four signal-to-noise ratios (−6, 0, +6, and +12 dB). ResultsWhile no differences existed in tone recognition in quiet between the two groups, the Bimodal group outperformed the Unilateral CI group under noise conditions. The differences between the two groups were significant at SNRs of 0, +6, and +12 dB in the SSN conditions (all p < 0.05), and at SNRs of +6 and +12 dB of TTB conditions (both p < 0.01), but not significant at other conditions (p > 0.05). The TTB exerted a greater masking effect than the SSN for tone recognition in the Unilateral CI group as well as in the Bimodal group at all SNRs tested (all p < 0.05). Among demographic or audiometric variables, only age at implantation showed a weak but significant correlation with the mean tone recognition performance under the SSN conditions (r = −0.276, p = 0.045). However, when Bonferroni correction was applied to the correlation analysis results, the weak correlation became not significant. ConclusionPrelingually-deafened children with CIs face challenges in tone perception in noisy environments, especially when the noise is fluctuating in amplitude such as the multi-talker babbles. Wearing a HA on the contralateral side when residual hearing permits is beneficial for tone recognition in noise.

Compensation or Preservation? Different Roles of Functional Lateralization in Speech Perception of Older Non-musicians and Musicians.

Musical training can counteract age-related decline in speech perception in noisy environments. However, it remains unclear whether older non-musicians and musicians rely on functional compensation or functional preservation to counteract the adverse effects of aging. This study utilized resting-state functional connectivity (FC) to investigate functional lateralization, a fundamental organization feature, in older musicians (OM), older non-musicians (ONM), and young non-musicians (YNM). Results showed that OM outperformed ONM and achieved comparable performance to YNM in speech-in-noise and speech-in-speech tasks. ONM exhibited reduced lateralization than YNM in lateralization index (LI) of intrahemispheric FC (LI_intra) in the cingulo-opercular network (CON) and LI of interhemispheric heterotopic FC (LI_he) in the language network (LAN). Conversely, OM showed higher neural alignment to YNM (i.e., a more similar lateralization pattern) compared to ONM in CON, LAN, frontoparietal network (FPN), dorsal attention network (DAN), and default mode network (DMN), indicating preservation of youth-like lateralization patterns due to musical experience. Furthermore, in ONM, stronger left-lateralized and lower alignment-to-young of LI_intra in the somatomotor network (SMN) and DAN and LI_he in DMN correlated with better speech performance, indicating a functional compensation mechanism. In contrast, stronger right-lateralized LI_intra in FPN and DAN and higher alignment-to-young of LI_he in LAN correlated with better performance in OM, suggesting a functional preservation mechanism. These findings highlight the differential roles of functional preservation and compensation of lateralization in speech perception in noise among elderly individuals with and without musical expertise, offering insights into successful aging theories from the lens of functional lateralization and speech perception.

A Bio-Inspired Probabilistic Neural Network Model for Noise-Resistant Collision Perception.

Bio-inspired models based on the lobula giant movement detector (LGMD) in the locust's visual brain have received extensive attention and application for collision perception in various scenarios. These models offer advantages such as low power consumption and high computational efficiency in visual processing. However, current LGMD-based computational models, typically organized as four-layered neural networks, often encounter challenges related to noisy signals, particularly in complex dynamic environments. Biological studies have unveiled the intrinsic stochastic nature of synaptic transmission, which can aid neural computation in mitigating noise. In alignment with these biological findings, this paper introduces a probabilistic LGMD (Prob-LGMD) model that incorporates a probability into the synaptic connections between multiple layers, thereby capturing the uncertainty in signal transmission, interaction, and integration among neurons. Comparative testing of the proposed Prob-LGMD model and two conventional LGMD models was conducted using a range of visual stimuli, including indoor structured scenes and complex outdoor scenes, all subject to artificial noise. Additionally, the model's performance was compared to standard engineering noise-filtering methods. The results clearly demonstrate that the proposed model outperforms all comparative methods, exhibiting a significant improvement in noise tolerance. This study showcases a straightforward yet effective approach to enhance collision perception in noisy environments.

Real-Time Implementation of a Frequency Shifter for Enhancement of Heart Sounds Perception on VLIW DSP Platform

Auscultation of heart sounds is important to perform cardiovascular assessment. External noises may limit heart sound perception. In addition, heart sound bandwidth is concentrated at very low frequencies, where the human ear has poor sensitivity. Therefore, the acoustic perception of the operator can be significantly improved by shifting the heart sound spectrum toward higher frequencies. This study proposes a real-time frequency shifter based on the Hilbert transform. Key system components are the Hilbert transformer implemented as a Finite Impulse Response (FIR) filter, and a Direct Digital Frequency Synthesizer (DDFS), which allows agile modification of the frequency shift. The frequency shifter has been implemented on a VLIW Digital Signal Processor (DSP) by devising a novel piecewise quadratic approximation technique for efficient DDFS implementation. The performance has been compared with other DDFS implementations both considering piecewise linear technique and sine/cosine standard library functions of the DSP. Piecewise techniques allow a more than 50% reduction in execution time compared to the DSP library. Piecewise quadratic technique also allows a more than 50% reduction in total required memory size in comparison to the piecewise linear. The theoretical analysis of the dynamic power dissipation exhibits a more than 20% reduction using piecewise techniques with respect to the DSP library. The real-time operation has been also verified on the DSK6713 rapid prototyping board by Texas Instruments C6713 DSP. Audiologic tests have also been performed to assess the actual improvement of heart sound perception. To this aim, heart sound recordings were corrupted by additive white Gaussian noise, crowded street noise, and helicopter noise, with different signal-to-noise ratios. All recordings were collected from public databases. Statistical analyses of the audiological test results confirm that the proposed approach provides a clear improvement in heartbeat perception in noisy environments.

Association between age-related hearing loss and cognitive decline

Background: Presbycusis, or age-related hearing loss, is a prevalent condition characterized by the gradual deterioration of hearing with age. The resulting impairments in auditory function lead to reduced speech perception in noisy environments and often have a negative impact on cognitive, behavioral, and psychosocial functions in the elderly population.Current Concepts: The proposed etiological mechanisms linking presbycusis to cognitive decline or dementia include the common-cause hypothesis, cognitive load hypothesis, cascade hypothesis, and overdiagnosis or harbinger hypothesis. Moreover, the challenges posed by the rapidly aging population in several countries, including Korea, highlight the increasing social impact of hearing loss and dementia. Consequently, interventions for hearing rehabilitation, such as the use of hearing aids and implantable hearing devices, have paramount importance in mitigating the adverse effects of hearing loss on cognitive impairment and dementia.Discussion and Conclusion: The implementation of prevention and rehabilitation programs for hearing loss in the elderly is crucial for alleviating the socioeconomic burden associated with the welfare of the aging population. However, many economically vulnerable elderly individuals reportedly do not use hearing aids, even though they experience considerable inconvenience resulting from hearing loss, primarily due to inadequate financial support. Therefore, implementing a comprehensive national policy to support hearing aid usage among elderly individuals with moderate hearing loss holds significant potential for reducing their risk of cognitive impairment and dementia.

Musician-Advantage on Listening Effort for Speech in Noise Perception: A Dual-Task Paradigm Measure.

Speech in noise (SIN) perception is essential for effective day-to-day communication, as everyday conversations seldom transpire in silent environments. Numerous studies have documented how musical training can aid in SIN discrimination through various neural-pathways, such as experience-dependent plasticity and overlapping processes between music and speech perception. However, empirical evidence regarding the impact of musical training on SIN perception remains inconclusive. This study aimed to investigate whether musicians trained in South Indian classical "Carnatic" style of music exhibited a distinct advantage over their non-musician counterparts in SIN perception. The study also attempted to explore whether the listening effort (LE) associated in this process was different across musicians and non-musicians, an area that has received limited attention. A quasi-experimental design was employed, involving two groups comprising 25 musicians and 35 non-musicians, aged 18-35 years, with normal hearing. In phase 1, participants' musical abilities were assessed using the Mini-Profile of Music Perception Skills (Mini-PROMS). In phase 2, SIN abilities were tested using the Tamil phonemically balanced words and Tamil Matrix Sentence Test at -5 dB, 0 dB, and +5 dB SNR. Phase 3 tested LE using a dual-task paradigm including auditory and visual stimuli as primary and secondary tasks. Fractional logit and linear regression models demonstrated that musicians outperformed non-musicians in the Mini-PROMS assessment. Musicians also fared better than non-musicians in SIN and LE at 0 dB SNR for words and +5 dB SNR for sentences. The findings of this study provided limited evidence to support the claim that musical training improves speech perception in noisy environments or reduces the associated listening effort.

No Musician Advantage in the Perception of Degraded-Fundamental Frequency Speech in Noisy Environments.

Pitch variations of the fundamental frequency (fo) contour contribute to speech perception in noisy environments, but whether musicians confer an advantage in speech in noise (SIN) with altered fo information remains unclear. This study investigated the effects of different levels of degraded fo contour (i.e., conveying lexical tone or intonation information) on musician advantage in speech-in-noise perception. A cohort of native Mandarin Chinese speakers, comprising 30 trained musicians and 30 nonmusicians, were tested on the intelligibility of Mandarin Chinese sentences with natural, flattened-tone, flattened-intonation, and flattened-all fo contours embedded in background noise masked under three signal-to-noise ratios (0, -5, and -9 dB). Pitch difference thresholds and innate musical skills associated with speech-in-noise benefits were also assessed. Speech intelligibility score improved with increasing signal-to-noise level for both musicians and nonmusicians. However, no musician advantage was observed for identifying any type of flattened-fo contour SIN. Musicians exhibited smaller fo pitch discrimination limens than nonmusicians, which correlated with benefits for perceiving speech with intact tone-level fo information. Regardless of musician status, performance on the pitch and accent musical-skill subtests correlated with speech intelligibility score. Collectively, these results provide no evidence for a musician advantage for perceiving speech with distorted fo information in noisy environments. Results further show that perceptual musical skills on pitch and accent processing may benefit the perception of SIN, independent of formal musical training. Our findings suggest that the potential application of music training in speech perception in noisy backgrounds is not contingent on the ability to process fo pitch contours, at least for Mandarin Chinese speakers. https://doi.org/10.23641/asha.23706354.

Performance of Sequentially Bilateral Cochlear Implanted Children Who Speak Mandarin

Introduction: Cochlear implantation is an effective treatment for children with deafness. Although the binaural effect of bilateral cochlear implantation on sound localization and speech perception in noisy environments has been demonstrated, the outcome and performance predictors of the second cochlear implant (CI2) remain uncertain for patients receiving sequential implantation. This study evaluated the hearing performance between the first cochlear implant (CI1), CI2, and bilateral cochlear implants (CI1+2) among children with sequential bilateral cochlear implantation. Methods: This single-center retrospective study enrolled 14 children and adolescents aged 8–18 years who underwent sequential bilateral cochlear implantation with a mean interimplant interval of 8.2 years. The Mandarin Lexical Neighborhood Test (M-LNT), the Mandarin Hearing in Noise Test (M-HINT), and the Comprehensive Cochlear Implant Questionnaire (CCIQ) scores of participants were evaluated. Mann-Whitney U tests and Spearman correlation analysis were performed to analyze factors associated with CI2 performance. Results: In the 1-year follow-up period after CI2 implantation, although the M-LNT mean score for CI2 was significantly lower than that for CI1, the M-LNT scores for CI2 and CI1+2 improved significantly over time. In a noisy environment, CI1+2 significantly outperformed CI1 in the M-HINT. The M-LNT score for CI2 was significantly associated with preoperative bimodal fitting, residual hearing of the second implanted ear, and CI2 daily-usage time. Specific to CI2, the CCIQ showed improvement 1 year after CI2 implantation. Conclusion: CI2 improved the hearing performance and quality of life of recipients with longer interimplant intervals, especially in noisy environments, and its efficacy was associated with preoperative bimodal fitting and regular daily use.

Automatic analysis of cochlear response using electrocochleography signals during cochlear implant surgery.

Cochlear implants (CIs) provide an opportunity for the hearing impaired to perceive sound through electrical stimulation of the hearing (cochlear) nerve. However, there is a high risk of losing a patient’s natural hearing during CI surgery, which has been shown to reduce speech perception in noisy environments as well as music appreciation. This is a major barrier to the adoption of CIs by the hearing impaired. Electrocochleography (ECochG) has been used to detect intra-operative trauma that may lead to loss of natural hearing. There is early evidence that ECochG can enable early intervention to save natural hearing of the patient. However, detection of trauma by observing changes in the ECochG response is typically carried out by a human expert. Here, we discuss a method of automating the analysis of cochlear responses during CI surgery. We establish, using historical patient data, that the proposed method is highly accurate (∼94% and ∼95% for sensitivity and specificity respectively) when compared to a human expert. The automation of real-time cochlear response analysis is expected to improve the scalability of ECochG and improve patient safety.

Differential Auditory and Visual Phase-Locking Are Observed during Audio-Visual Benefit and Silent Lip-Reading for Speech Perception.

Speech perception in noisy environments is enhanced by seeing facial movements of communication partners. However, the neural mechanisms by which audio and visual speech are combined are not fully understood. We explore MEG phase-locking to auditory and visual signals in MEG recordings from 14 human participants (6 females, 8 males) that reported words from single spoken sentences. We manipulated the acoustic clarity and visual speech signals such that critical speech information is present in auditory, visual, or both modalities. MEG coherence analysis revealed that both auditory and visual speech envelopes (auditory amplitude modulations and lip aperture changes) were phase-locked to 2-6 Hz brain responses in auditory and visual cortex, consistent with entrainment to syllable-rate components. Partial coherence analysis was used to separate neural responses to correlated audio-visual signals and showed non-zero phase-locking to auditory envelope in occipital cortex during audio-visual (AV) speech. Furthermore, phase-locking to auditory signals in visual cortex was enhanced for AV speech compared with audio-only speech that was matched for intelligibility. Conversely, auditory regions of the superior temporal gyrus did not show above-chance partial coherence with visual speech signals during AV conditions but did show partial coherence in visual-only conditions. Hence, visual speech enabled stronger phase-locking to auditory signals in visual areas, whereas phase-locking of visual speech in auditory regions only occurred during silent lip-reading. Differences in these cross-modal interactions between auditory and visual speech signals are interpreted in line with cross-modal predictive mechanisms during speech perception.SIGNIFICANCE STATEMENT Verbal communication in noisy environments is challenging, especially for hearing-impaired individuals. Seeing facial movements of communication partners improves speech perception when auditory signals are degraded or absent. The neural mechanisms supporting lip-reading or audio-visual benefit are not fully understood. Using MEG recordings and partial coherence analysis, we show that speech information is used differently in brain regions that respond to auditory and visual speech. While visual areas use visual speech to improve phase-locking to auditory speech signals, auditory areas do not show phase-locking to visual speech unless auditory speech is absent and visual speech is used to substitute for missing auditory signals. These findings highlight brain processes that combine visual and auditory signals to support speech understanding.

Deep Learning-Based Speech Enhancement With a Loss Trading Off the Speech Distortion and the Noise Residue for Cochlear Implants.

The cochlea plays a key role in the transmission from acoustic vibration to neural stimulation upon which the brain perceives the sound. A cochlear implant (CI) is an auditory prosthesis to replace the damaged cochlear hair cells to achieve acoustic-to-neural conversion. However, the CI is a very coarse bionic imitation of the normal cochlea. The highly resolved time-frequency-intensity information transmitted by the normal cochlea, which is vital to high-quality auditory perception such as speech perception in challenging environments, cannot be guaranteed by CIs. Although CI recipients with state-of-the-art commercial CI devices achieve good speech perception in quiet backgrounds, they usually suffer from poor speech perception in noisy environments. Therefore, noise suppression or speech enhancement (SE) is one of the most important technologies for CI. In this study, we introduce recent progress in deep learning (DL), mostly neural networks (NN)-based SE front ends to CI, and discuss how the hearing properties of the CI recipients could be utilized to optimize the DL-based SE. In particular, different loss functions are introduced to supervise the NN training, and a set of objective and subjective experiments is presented. Results verify that the CI recipients are more sensitive to the residual noise than the SE-induced speech distortion, which has been common knowledge in CI research. Furthermore, speech reception threshold (SRT) in noise tests demonstrates that the intelligibility of the denoised speech can be significantly improved when the NN is trained with a loss function bias to more noise suppression than that with equal attention on noise residue and speech distortion.

Central auditory processing deficits in schizophrenia: Effects of auditory-based cognitive training

BackgroundSensory processing abnormalities are common in schizophrenia (SZ) and impact everyday functions, such as speech perception in noisy environments. Auditory-based targeted cognitive training (TCT) is a “bottom up” cognitive remediation intervention designed to enhance the speed and accuracy of low-level auditory information processing. However, the effects of TCT on behavioral measures of central auditory processing (CAP) and the role of CAP function on verbal learning outcomes in SZ are unknown. MethodsSZ (n = 42) and healthy subjects (CTL; n = 18) underwent comprehensive clinical, neurocognitive, and auditory assessments, including tests of hearing sensitivity and speech recognition (Words-in-Noise (WIN), Quick Speech-in-Noise (SIN)). SZ patients were randomized to receive either treatment-as-usual (TAU); or 30-h of TCT + TAU using a stratified, parallel design. SZ patients repeated assessments ~10–12 weeks later. ResultsPatients exhibited deficits in both WIN (p < 0.05, d = 0.50) and SIN (p < 0.01, d = 0.63). A treatment × time interaction on WIN (p < 0.05, d = 0.74), but not SIN discriminability, was seen in the TCT group relative to TAU. Specific enhancements in the 4-dB over background range drove gains in WIN performance. Moreover, SZ patients with greater CAP deficits experienced robust gains in verbal learning after 30-h of TCT relative to SZ patients without CAP impairment (p < 0.01, d = 1.28). ConclusionFindings demonstrate that intensive auditory training enhances the fidelity of auditory processing and perception, such that specific CAP deficits were ‘normalized’ and were predictive of gains in verbal learning after TCT. It is conceivable that patients with deficiencies in CAP measures may benefit most from TCT and other interventions targeting auditory dysfunction in SZ.

Neuronal figure-ground responses in primate primary auditory cortex.

SummaryFigure-ground segregation, the brain’s ability to group related features into stable perceptual entities, is crucial for auditory perception in noisy environments. The neuronal mechanisms for this process are poorly understood in the auditory system. Here, we report figure-ground modulation of multi-unit activity (MUA) in the primary and non-primary auditory cortex of rhesus macaques. Across both regions, MUA increases upon presentation of auditory figures, which consist of coherent chord sequences. We show increased activity even in the absence of any perceptual decision, suggesting that neural mechanisms for perceptual grouping are, to some extent, independent of behavioral demands. Furthermore, we demonstrate differences in figure encoding between more anterior and more posterior regions; perceptual saliency is represented in anterior cortical fields only. Our results suggest an encoding of auditory figures from the earliest cortical stages by a rate code.

Dynamic visual noise promotes social attraction, but does not affect group size preference, in a shoaling fish

Gathering information from the environment allows animals to make informed behavioural decisions, with individuals sampling information either privately or via social cues from group members. Environmental noise, however, may disrupt the ability of animals to gather information in their environment. Therefore, social interactions could be disrupted by environmental noise, or adapted to mitigate the costs associated with compromised perception in noisy environments. Here we tested whether the presence of water caustics, a natural form of visual noise prevalent within shallow aquatic habitats, affects the social decisions of shoaling fish. In a classic experimental paradigm, individual three-spined sticklebacks, Gasterosteus aculeatus, were given a choice between two conspecific shoals differing in size while immersed in different levels of visual noise. Fish showed greater social attraction towards conspecifics as noise levels increased, measured by a reduction in the distance they maintained from others. While sticklebacks only showed clear preferences for groups that had at least four more members than another group, there was no evidence that visual noise level influenced fish's preference to associate with these larger shoals, nor did it change the preferences for other shoal sizes. Our findings suggest that, at the group sizes tested, visual noise increases individual stickleback's social attraction towards conspecifics, but does not affect their decision to associate with the larger of two groups. Such changes to social behaviour may reflect the consequences of having a reduced ability to sample private, but not social, information in noisy environments.

Effects of auditory processing training on speech perception and brainstem plastisity in adolescents with autism spectrum disorders.

ObjectiveAutism spectrum disorder (ASD) is a neurodevelopmental disorder. A major problem of ASD is speech perception impairment in the presence of background noise. Additionally, researchers have reported temporal auditory processing impairment in patients with ASD. In the present study, we evaluated the effects of a temporal-based training program on improvement of speech perception in the presence of noise using the speech auditory brainstem response (sABR).Materials & MethodsTwenty-eight adolescents with high functional ASD with the mean age of 14.35±1.86 years were randomly selected and divided into an ASD group (11 males and three females) and a control group (13 males and one female). All the subjects had a normal hearing and intelligence threshold and had no history of neurological disorder.A speech perception test was performed in signal-to-noise ratios of 0 and +10. The intervention group received a temporal processingbased auditory training program, and the control group received a conventional training program. A P-value of <0.05 was considered significant.ResultsAfter training, speech perception in the presence of noise was significantly higher (P <0.001) and the latency of all sABR waves was lower in the intervention group compared to the control group.ConclusionImprovement of speech perception in noisy environments and the reduced latency of sABR waves following a temporal processingbased training program highlight the role of brainstem neural plasticity in speech processing.

Strategies of hearing aids fitting for improving speech recognition in noisy environments

To assess speech recognition in users of mono- and binaural hearing aids (HA) with dynamic environment control system (DECS). 25 HA users with symmetrical bilateral moderate to severe sensorineural hearing loss and 10 individuals with normal hearing underwent speech audiometry in a free sound field by listening to an adaptive Russian matrix sentence test with a background noise. The testing was conducted for hearing impaired patients with one and two HA. The Speech Recognition Thresholds in noise (SRTN) using HA with DESC and using HA without DESC were compared. The dichotic digits test and the rapidly alternating speech perception test were performed to evaluate the central auditory system function. The SRTN in normal hearing listeners was -16.4±1.9 dB SNR. In the case of monaural using HA without DESC the SRTN was -2.5±4.4 dB SNR, using HA with DESC it was -5.8±4.0 dB SNR; in the case of using binaural HAs it was -6.3±3.8 dB SNR and -9.9±3.1 dB SNR accordingly. HAs with Dynamic Environment Control System are highly effective for speech perception in noisy environments. Binaural HA use is more effective than monaural HA use regardless of HA model. Speech recognition in noisy environments in cases of binaural HA use correlates significantly with results of tests assessing the central auditory system function.

Digital enhancement of speech perception in noisy environments

If speech is reproduced in an acoustically disturbed environment via a loudspeaker, the perception in terms of intelligibility or listening effort may be impaired. Typical situations arise in connection with mobile phones or public address systems. The location of the listener is called the near-end while the speech signal is received from the far-end. Usually, the acoustical background noise cannot be influenced, but speech perception may be enhanced by digital pre-processing of the loudspeaker signal. This pre-processing technique is called Near-End Listening Enhancement (NELE). The received signal is filtered adaptively, by taking the instantaneous characteristics of the background noise into account and by exploiting psychoacoustic properties of the auditory system such as the masking threshold. The increase of the loudspeaker volume is often not allowed or very limited, to avoid injury of hearing or damages of the loudspeaker and because of the listening comfort. In this contribution, state-of-the-art NELE algorithms operating in the short-term frequency domain are reviewed and novel time domain approaches are presented. Furthermore, the differing NELE constraints of public address systems and mobile phones are discussed.

Decoding Hearing-Related Changes in Older Adults' Spatiotemporal Neural Processing of Speech Using Machine Learning.

Speech perception in noisy environments depends on complex interactions between sensory and cognitive systems. In older adults, such interactions may be affected, especially in those individuals who have more severe age-related hearing loss. Using a data-driven approach, we assessed the temporal (when in time) and spatial (where in the brain) characteristics of cortical speech-evoked responses that distinguish older adults with or without mild hearing loss. We performed source analyses to estimate cortical surface signals from the EEG recordings during a phoneme discrimination task conducted under clear and noise-degraded conditions. We computed source-level ERPs (i.e., mean activation within each ROI) from each of the 68 ROIs of the Desikan-Killiany (DK) atlas, averaged over a randomly chosen 100 trials without replacement to form feature vectors. We adopted a multivariate feature selection method called stability selection and control to choose features that are consistent over a range of model parameters. We use parameter optimized support vector machine (SVM) as a classifiers to investigate the time course and brain regions that segregate groups and speech clarity. For clear speech perception, whole-brain data revealed a classification accuracy of 81.50% [area under the curve (AUC) 80.73%; F1-score 82.00%], distinguishing groups within ∼60 ms after speech onset (i.e., as early as the P1 wave). We observed lower accuracy of 78.12% [AUC 77.64%; F1-score 78.00%] and delayed classification performance when speech was embedded in noise, with group segregation at 80 ms. Separate analysis using left (LH) and right hemisphere (RH) regions showed that LH speech activity was better at distinguishing hearing groups than activity measured in the RH. Moreover, stability selection analysis identified 12 brain regions (among 1428 total spatiotemporal features from 68 regions) where source activity segregated groups with >80% accuracy (clear speech); whereas 16 regions were critical for noise-degraded speech to achieve a comparable level of group segregation (78.7% accuracy). Our results identify critical time-courses and brain regions that distinguish mild hearing loss from normal hearing in older adults and confirm a larger number of active areas, particularly in RH, when processing noise-degraded speech information.

Neuronal Figure-Ground Responses in Primate Primary Auditory Cortex

Figure-ground segregation is crucial for auditory perception in noisy environments, where the brain needs to group spectrotemporally overlapping sound objects into stable perceptual entities. The neuronal mechanisms of this process are poorly understood. Here we report figure-ground modulation (FGM) present in single-, multi-unit, as well as local field potential responses across primary core and adjacent belt areas in the macaque monkey.