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Background and Aim: The Acceptable Noise Level (ANL), which is an effective clinical tool for quantitative assessment of noise tolerance, is affected by some known variables related to both subject and testing materials. The present study examined how the characteristics of different babble noises may affect the ANL results in normal adult listeners. Methods: Forty Persian listeners with normal hearing participated. In addition to typical ANL testing with 12-talker noise, the ANL was obtained in 8 different conditions varying in number of talkers from 2 to 10 in the babble noises presenting forward and backward. Results: There was a significantly lower ANL for 2-talker babble compared to 4, 8, 10, and 12-talker babble in both forward and backward noise conditions. With the increase in talkers in noise, the ANL becomes worse but reaches almost a plateau with more than 4 talkers in babble noise. There was a statistically significant difference between 2-talker forward and 2-talker backward noises, with no difference for the other conditions. Conclusion: This finding that the ANL is affected by the number of talkers in babble noise and by the forward and backward background noise suggests that informational masking and listening in dip mechanisms are involved in ANL for normal hearing people at least. [ABSTRACT FROM AUTHOR]

Simple Summary: Many individuals report difficulty perceiving speech in background noise. Research has shown that one factor in this type of processing is the effect of noise on the brain's response to speech. Different types of noise affect the strength of the neural encoding of speech to varying degrees, with greater informational masking causing greater degradation. Previous research has focused on the effects of attention in noise, which tends to enhance the neural encoding of the speech signal via inhibitory mechanisms. However, there is a pre-attentive stage of inhibition, sensory gating, which has been linked to speech perception in noise. The impact of noise on the neural response during this phase remains unclear. This preliminary study investigated the gating response, recorded via high-density EEG in fifteen normal-hearing adults, in quiet and noise conditions with low and high informational masking. Scalp maps were generated to observe brain activation in each condition. Significant gating occurred in quiet, while noise conditions resulted in a significantly decreased gating response. The gating function was significantly degraded in noise with less informational masking content, coinciding with a reduced activation of inhibitory gating networks. These findings illustrate the adverse effect of noise on pre-attentive inhibition related to speech perception. Cortical auditory evoked potentials (CAEPs) indicate that noise degrades auditory neural encoding, causing decreased peak amplitude and increased peak latency. Different types of noise affect CAEP responses, with greater informational masking causing additional degradation. In noisy conditions, attention can improve target signals' neural encoding, reflected by an increased CAEP amplitude, which may be facilitated through various inhibitory mechanisms at both pre-attentive and attentive levels. While previous research has mainly focused on inhibition effects during attentive auditory processing in noise, the impact of noise on the neural response during the pre-attentive phase remains unclear. Therefore, this preliminary study aimed to assess the auditory gating response, reflective of the sensory inhibitory stage, to repeated vowel pairs presented in background noise. CAEPs were recorded via high-density EEG in fifteen normal-hearing adults in quiet and noise conditions with low and high informational masking. The difference between the average CAEP peak amplitude evoked by each vowel in the pair was compared across conditions. Scalp maps were generated to observe general cortical inhibitory networks in each condition. Significant gating occurred in quiet, while noise conditions resulted in a significantly decreased gating response. The gating function was significantly degraded in noise with less informational masking content, coinciding with a reduced activation of inhibitory gating networks. These findings illustrate the adverse effect of noise on pre-attentive inhibition related to speech perception. [ABSTRACT FROM AUTHOR]

Cortical auditory evoked potentials (CAEPs) indicate that noise degrades auditory neural encoding, causing decreased peak amplitude and increased peak latency. Different types of noise affect CAEP responses, with greater informational masking causing additional degradation. In noisy conditions, attention can improve target signals’ neural encoding, reflected by an increased CAEP amplitude, which may be facilitated through various inhibitory mechanisms at both pre-attentive and attentive levels. While previous research has mainly focused on inhibition effects during attentive auditory processing in noise, the impact of noise on the neural response during the pre-attentive phase remains unclear. Therefore, this preliminary study aimed to assess the auditory gating response, reflective of the sensory inhibitory stage, to repeated vowel pairs presented in background noise. CAEPs were recorded via high-density EEG in fifteen normal-hearing adults in quiet and noise conditions with low and high informational masking. The difference between the average CAEP peak amplitude evoked by each vowel in the pair was compared across conditions. Scalp maps were generated to observe general cortical inhibitory networks in each condition. Significant gating occurred in quiet, while noise conditions resulted in a significantly decreased gating response. The gating function was significantly degraded in noise with less informational masking content, coinciding with a reduced activation of inhibitory gating networks. These findings illustrate the adverse effect of noise on pre-attentive inhibition related to speech perception.

Background and Aim: The Acceptable Noise Level (ANL), which is an effective clinical tool for quantitative assessment of noise tolerance, is affected by some known variables related to both subject and testing materials. The present study examined how the characteristics of different babble noises may affect the ANL results in normal adult listeners. Methods: Forty Persian listeners with normal hearing participated. In addition to typical ANL testing with 12-talker noise, the ANL was obtained in 8 different conditions varying in number of talkers from 2 to 10 in the babble noises presenting forward and backward. Results: There was a significantly lower ANL for 2-talker babble compared to 4, 8, 10, and 12-talker babble in both forward and backward noise conditions. With the increase in talkers in noise, the ANL becomes worse but reaches almost a plateau with more than 4 talkers in babble noise. There was a statistically significant difference between 2-talker forward and 2-talker backward noises, with no difference for the other conditions. Conclusion: This finding that the ANL is affected by the number of talkers in babble noise and by the forward and backward background noise suggests that informational masking and listening in dip mechanisms are involved in ANL for normal hearing people at least.

Everyday speech communication often occurs in environments with background noise, and the impact of noise on speech recognition can vary depending on factors such as noise type, noise intensity, and the listener's hearing ability. However, the extent to which neural mechanisms in speech understanding are influenced by different types and levels of noise remains unknown. This study aims to investigate whether individuals exhibit distinct neural responses and attention strategies depending on noise conditions. We recorded electroencephalography (EEG) data from 20 participants with normal hearing (13 males) and evaluated both neural tracking of speech envelopes and behavioral performance in speech understanding in the presence of varying types of background noise. Participants engaged in an EEG experiment consisting of two separate sessions. The first session involved listening to a 12-min story presented binaurally without any background noise. In the second session, speech understanding scores were measured using matrix sentences presented under speech-shaped noise (SSN) and Story noise background noise conditions at noise levels corresponding to sentence recognitions score (SRS). We observed differences in neural envelope correlation depending on noise type but not on its level. Interestingly, the impact of noise type on the variation in envelope tracking was more significant among participants with higher speech perception scores, while those with lower scores exhibited similarities in envelope correlation regardless of the noise condition. The findings suggest that even individuals with normal hearing could adopt different strategies to understand speech in challenging listening environments, depending on the type of noise. [ABSTRACT FROM AUTHOR]

Different from normal-hearing (NH) listeners, speech recognition thresholds (SRTs) in cochlear implant (CI) users are typically poorer with dynamic maskers than with speech-spectrum noise (SSN). The effectiveness of different masker types may depend on their acoustic and linguistic characteristics. The goal of the present study was to evaluate the effectiveness of different masker types with varying acoustic and linguistic properties in CI and NH listeners. SRTs were measured with nine maskers, including SSN, dynamic nonspeech maskers, and speech maskers with or without lexical content. Results showed that CI users performed significantly poorer than NH listeners with all maskers. NH listeners were much more sensitive to masker type than were CI users. Relative to SSN, NH listeners experienced significant masking release for most maskers, which could be well explained by the glimpse proportion, especially for maskers containing similar cues related to fundamental frequency or lexical content. In contrast, CI users generally experienced negative masking release. There was significant intercorrelation among the maskers for CI users' SRTs but much less so for NH listeners' SRTs. Principal component analysis showed that one factor explained 72% of the variance in CI users' SRTs but only 55% in NH listeners' SRTs across all maskers. Taken together, the results suggest that SRTs in SSN largely accounted for the variability in CI users' SRTs with dynamic maskers. Different from NH listeners, CI users appear to be more susceptible to energetic masking and do not experience a release from masking with dynamic envelopes or speech maskers. [ABSTRACT FROM AUTHOR]

Albert Feng was a pioneer in the field of auditory neuroethology who used frogs to investigate the neural basis of spectral and temporal processing and directional hearing. Among his many contributions was connecting neural mechanisms for sound pattern recognition and localization to the problems of auditory masking that frogs encounter when communicating in noisy, real-world environments. Feng's neurophysiological studies of auditory processing foreshadowed and inspired subsequent behavioral investigations of auditory masking in frogs. For frogs, vocal communication frequently occurs in breeding choruses, where males form dense aggregations and produce loud species-specific advertisement calls to attract potential mates and repel competitive rivals. In this review, we aim to highlight how Feng's research advanced our understanding of how frogs cope with noise. We structure our narrative around three themes woven throughout Feng's research—spectral, temporal, and directional processing—to illustrate how frogs can mitigate problems of auditory masking by exploiting frequency separation between signals and noise, temporal fluctuations in noise amplitude, and spatial separation between signals and noise. We conclude by proposing future research that would build on Feng's considerable legacy to advance our understanding of hearing and sound communication in frogs and other vertebrates. [ABSTRACT FROM AUTHOR]

Different from normal-hearing (NH) listeners, speech recognition thresholds (SRTs) in cochlear implant (CI) users are typically poorer with dynamic maskers than with speech-spectrum noise (SSN). The effectiveness of different masker types may depend on their acoustic and linguistic characteristics. The goal of the present study was to evaluate the effectiveness of different masker types with varying acoustic and linguistic properties in CI and NH listeners. SRTs were measured with nine maskers, including SSN, dynamic nonspeech maskers, and speech maskers with or without lexical content. Results showed that CI users performed significantly poorer than NH listeners with all maskers. NH listeners were much more sensitive to masker type than were CI users. Relative to SSN, NH listeners experienced significant masking release for most maskers, which could be well explained by the glimpse proportion, especially for maskers containing similar cues related to fundamental frequency or lexical content. In contrast, CI users generally experienced negative masking release. There was significant intercorrelation among the maskers for CI users' SRTs but much less so for NH listeners' SRTs. Principal component analysis showed that one factor explained 72% of the variance in CI users' SRTs but only 55% in NH listeners' SRTs across all maskers. Taken together, the results suggest that SRTs in SSN largely accounted for the variability in CI users' SRTs with dynamic maskers. Different from NH listeners, CI users appear to be more susceptible to energetic masking and do not experience a release from masking with dynamic envelopes or speech maskers. [ABSTRACT FROM AUTHOR]

Background and Aim: Generally, in noisy environments more informational masking occurs. Older adults benefit less than younger adults from spatial hearing and they have more problems of understanding speech in the presence of distracting speeches. This study was conducted to examine the effect of auditory spatial training on informational masking release in the elderly. Methods: Thirty-two 60-75-year-olds with normal hearing, who complain about difficulty in speech perception in noise, participated in control and intervention groups (16 people in each group). The intervention included fifteen sessions of auditory spatial training. The informational masking measurement test scores were compared before the intervention, one session after the intervention, and one month after between the two groups. Results: There was a significant improvement in informational masking measurement scores in the intervention group compared to the control (p<0.02). The results showed no significant differences between the informational masking measurement scores before and after the intervention in the control group (p>0.05) and a significant difference in most signal to noise ratio i.e. 0, -5 and -10, in the intervention group (p=0.006). No significant difference was found between the results of the two assessments one session and one month after the intervention in any of the positions (p>0.05), which suggests that both groups' scores remained highly stable one month after the intervention Conclusion: This study introduced a spatial training program to improve speech perception in noise in normal-hearing elderly listeners. It was recommended that this kind of training be included in geriatric population auditory rehabilitation programs. [ABSTRACT FROM AUTHOR]

• Listeners benefit from visually guided cues for the timing of syllables in noise. • Visual cues are redundant when there are auditory temporal cues from speech rhythm. • Visual cues are more effective at reducing informational than energetic masking. This study examined the effect of visual cues that provide the timing information of syllables in nonsense target sentences on the recognition of target speech against either a speech-spectrum noise masker or a two-talker masker. When the target sentences with normally regular rhythm were used (Experiment 1), visual cues indicating the onset times of the target-sentence syllables did not significantly improve target-speech recognition against either the speech-spectrum noise masker or the two-talker masker. On the other hand, recognition of the last (third) keyword in these normal rhythmic sentences was significantly better than that of the first keyword against the two-talker masker, but not the noise masker. This word-position-related speech-recognition improvement indicates a beneficial role of regular speech rhythm in release from informational masking due to the temporal prediction of target-sentence syllables. When artificially irregular rhythms were introduced into target sentences (Experiment 2), visual cues indicating syllable onset times significantly improved target-speech recognition against both types of masker. Moreover, the visual-cue-induced improvement in speech recognition against the two-talker masker was significantly larger than that against the speech-spectrum noise masker. The results of this study suggested that visual cues indicating target-syllable timing information improve target-speech recognition against competing maskers only when the temporal rhythmic regularity of target speech sentences is reduced. [ABSTRACT FROM AUTHOR]

Subjective tinnitus patients experience more hearing difficulties than normal peers in complex hearing environments, even though most of these patients have normal pure-tone hearing thresholds. Using speech recognition tasks under different masking conditions can provide insight into whether the effects of tinnitus are lateralized and the mechanisms behind the effects. By simulating sound field recordings, we obtain a target speech sentence that can be perceived as presented on one side and noise or speech masking with or without spatial separation from it. Our study used the virtual sound field technique to investigate the difference in speech recognition ability between chronic subjective tinnitus patients and a normal-hearing control group under the four masking conditions (speech-spectrum noise masking or two-talker speech masking, with or without perceived spatial separation). Experiment 1 showed no differences for target speech perceived location (left or right), which rules out a lateralization of the effect of tinnitus patients. Experiment 2 further found that although tinnitus patients had weaker performance than normal people in very complex auditory scenarios, when the spatial cue of the target speech exists, they can make good use of this cue to make up for the original processing disadvantage and achieve a similar performance as the normal-hearing group. In addition, the current study distinguished the effects of informational masking and energetic masking on speech recognition in patients with tinnitus and normal hearing. The results suggest that the impact of tinnitus on speech recognition in patients is more likely to occur in the auditory center rather than the periphery.

Prepulse inhibition (PPI) is the reduction in the acoustic startle reflex (ASR) when the startling stimulus (pulse) is preceded by a weaker, non-starting stimulus. This can be enhanced by facilitating selective attention to the prepulse against a noise-masking background. On the other hand, the facilitation of selective attention to a target speech can release the target speech from masking, particularly from speech informational masking. It is not clear whether attentional regulation also affects PPI in this kind of auditory masking. This study used a speech syllable as the prepulse to examine whether the masker type and perceptual spatial attention can affect the PPI or the scalp EEG responses to the prepulse in healthy younger-adult humans, and whether the ERPs evoked by the prepulse can predict the PPI intensity of the ASR. The results showed that the speech masker produced a larger masking effect than the noise masker, and the perceptual spatial separation facilitated selective attention to the prepulse, enhancing both the N1 component of the prepulse syllable and the PPI of the ASR, particularly when the masker was speech. In addition, there was no significant correlation between the PPI and ERPs under any of the conditions, but the perceptual separation-induced PPI enhancement and ERP N1P2 peak-to-peak amplitude enhancement were correlated under the speech-masking condition. Thus, the attention-mediated PPI is useful for differentiating noise energetic masking and speech informational masking, and the perceptual separation-induced release of the prepulse from informational masking is more associated with attention-mediated early cortical unmasking processing than with energetic masking. However, the processes for the PPI of the ASR and the cortical responses to the prepulse are mediated by different neural mechanisms. [ABSTRACT FROM AUTHOR]

Speech understanding in noisy situations is compromised in old age. This study investigated the energetic and informational masking components of multi‐talker babble noise and their influence on neural tracking of the speech envelope in a sample of healthy older adults. Twenty‐three older adults (age range 65–80 years) listened to an audiobook embedded in noise while their electroencephalogram (EEG) was recorded. Energetic masking was manipulated by varying the signal‐to‐noise ratio (SNR) between target speech and background talkers and informational masking was manipulated by varying the number of background talkers. Neural envelope tracking was measured by calculating temporal response functions (TRFs) between speech envelope and EEG. Number of background talkers, but not SNR modulated the amplitude of an earlier (around 50 ms time lag) and a later (around 300 ms time lag) peak in the TRFs. Selective attention, but not working memory or peripheral hearing additionally modulated the amplitude of the later TRF peak. Finally, amplitude of the later TRF peak was positively related to accuracy in the comprehension task. The results suggest that stronger envelope tracking is beneficial for speech‐in‐noise understanding and that selective attention is an important ability supporting speech‐in‐noise understanding in multi‐talker scenes. [ABSTRACT FROM AUTHOR]

Prepulse inhibition (PPI) is the reduction in the acoustic startle reflex (ASR) when the startling stimulus (pulse) is preceded by a weaker, non-starting stimulus. This can be enhanced by facilitating selective attention to the prepulse against a noise-masking background. On the other hand, the facilitation of selective attention to a target speech can release the target speech from masking, particularly from speech informational masking. It is not clear whether attentional regulation also affects PPI in this kind of auditory masking. This study used a speech syllable as the prepulse to examine whether the masker type and perceptual spatial attention can affect the PPI or the scalp EEG responses to the prepulse in healthy younger-adult humans, and whether the ERPs evoked by the prepulse can predict the PPI intensity of the ASR. The results showed that the speech masker produced a larger masking effect than the noise masker, and the perceptual spatial separation facilitated selective attention to the prepulse, enhancing both the N1 component of the prepulse syllable and the PPI of the ASR, particularly when the masker was speech. In addition, there was no significant correlation between the PPI and ERPs under any of the conditions, but the perceptual separation-induced PPI enhancement and ERP N1P2 peak-to-peak amplitude enhancement were correlated under the speech-masking condition. Thus, the attention-mediated PPI is useful for differentiating noise energetic masking and speech informational masking, and the perceptual separation-induced release of the prepulse from informational masking is more associated with attention-mediated early cortical unmasking processing than with energetic masking. However, the processes for the PPI of the ASR and the cortical responses to the prepulse are mediated by different neural mechanisms.

Background and Aim: In noisy environments, two types of masking including energetic masking (EM) and informational masking (IM) occur. EM results from the spectral overlap of the target and maskers on the basilar membrane, while IM occurs at higher level. This paper aimed to review the concept of IM in terms of historical perspective and definitions, the important cues for releasing from it, age-related effects and its neural basis. Recent Findings: The data from psychoacoustic, behavioral, and neuro-imaging studies were reviewed and discussed in order to provide an overall image of IM. According to these studies, it seems that perceptual segregation between the target and maskers is the most important cues for releasing from IM. This process takes place simply and without any effort in adults with normal hearing; however, it does not occur easily in children, elderly people and those with impaired hearing. Moreover, it seems that both top-down and bottom-up processing are involved in IM formation. Conclusion: Since IM leads to failure in selection of auditory objects and prevents the individual from auditory scene analysis, understanding the IM concept leads to a better knowledge of speech perception in noise. [ABSTRACT FROM AUTHOR]

Background: Regarding the strong auditory spatial plasticity capability of the central auditory system and the effect of short-term and long-term rehabilitation programs in elderly people, it seems that an auditory spatial training can help this population in informational masking release and better track speech in noisy environments. The main purposes of this study are developing an informational masking measurement test and an auditory spatial training program. Protocol: This study will be conducted in two parts. Part 1: develop and determine the validity of an informational masking measurement test by recruiting two groups of young (n=50) and old (n=50) participants with normal hearing who have no difficulty in understanding speech in noisy environments. Part 2 (clinical trial): two groups of 60-75-year-olds with normal hearing, who complain about difficulty in speech perception in noisy environments, will participate as control and intervention groups to examine the effect of auditory spatial training. Intervention: 15 sessions of auditory spatial training. The informational masking measurement test and Speech, Spatial and Qualities of Hearing Scale will be compared before intervention, immediately after intervention, and five weeks after intervention between the two groups. Discussion: Since auditory training programs do not deal with informational masking release, an auditory spatial training will be designed, aiming to improve hearing in noisy environments for elderly populations. Trial registration: Iranian Registry of Clinical Trials ( IRCT20190118042404N1) on 25 th February 2019.

Background: Regarding the strong auditory spatial plasticity capability of the central auditory system and the effect of short-term and long-term rehabilitation programs in elderly people, it seems that an auditory spatial training can help this population in informational masking release and better track speech in noisy environments. The main purposes of this study are developing an informational masking measurement test and an auditory spatial training program. Protocol: This study will be conducted in two parts. Part 1: develop and determine the validity of an informational masking measurement test by recruiting two groups of young (n=50) and old (n=50) participants with normal hearing who have no difficulty in understanding speech in noisy environments. Part 2 (clinical trial): two groups of 60-75-year-olds with normal hearing, who complain about difficulty in speech perception in noisy environments, will participate as control and intervention groups to examine the effect of auditory spatial training. Intervention: 8 sessions of auditory spatial training. The informational masking measurement test and Speech, Spatial and Qualities of Hearing Scale will be compared before intervention, immediately after intervention, and one month after intervention between the two groups. Discussion: Since auditory training programs do not deal with informational masking release, an auditory spatial training will be designed, aiming to improve hearing in noisy environments for elderly populations. Trial registration: Iranian Registry of Clinical Trials ( IRCT20190118042404N1) on 25 th February 2019.

This study considers whether bilingual children listening in a second language are among those on which higher processing and cognitive demands are placed when noise is present. Forty‐four Swedish sequential bilingual 15 year‐olds were given memory span and vocabulary assessments in their first and second language (Swedish and English). First and second language speech reception thresholds (SRTs) at 50% intelligibility for numbers and colors presented in noise were obtained using an adaptive procedure. The target sentences were presented in simulated, virtual classroom acoustics, masked by either 16‐talker multi‐talker babble noise (MTBN) or speech shaped noise (SSN), positioned either directly in front of the listener (collocated with the target speech), or spatially separated from the target speech by 90° to either side. Main effects in the Spatial and Noise factors indicated that intelligibility was 3.8 dB lower in collocated conditions and 2.9 dB lower in MTBN conditions. SRTs were unexpectedly higher by 0.9 dB in second language conditions. Memory span significantly predicted 17% of the variance in the second language SRTs, and 9% of the variance in first language SRTs, indicating the possibility that the SRT task places higher cognitive demands when listening to second language speech than when the target is in the listener's first language. [ABSTRACT FROM AUTHOR]

Individuals with autism spectrum disorder (ASD) exhibit atypical speech-in-noise (SiN) perception, but the scope of these impairments has not been clearly defined. We conducted a systematic review of the behavioural research on SiN perception in ASD, using a comprehensive search strategy across databases (Embase, Pubmed, Web of Science, APA PsycArticles, LLBA, clinicaltrials.gov and PsyArXiv). We withheld 20 studies that generally revealed intact speech perception in stationary noise, while impairments in speech discrimination were found in temporally modulated noise, concurrent speech, and audiovisual speech perception. An association with auditory temporal processing deficits, exacerbated by suboptimal language skills, is shown. Speech-in-speech perception might be further impaired due to deficient top-down processing of speech. Further research is needed to address remaining challenges and gaps in our understanding of these impairments, including the developmental aspects of SiN processing in ASD, and the impact of gender and social attentional orienting on this ability. Our findings have important implications for improving communication in ASD, both in daily interactions and in clinical and educational settings. • Autistic children may be less capable to perceive speech in steady-state noise. • Autistic temporal processing deficits hinder speech perception in noise. • Language delay seems associated with autistic temporal processing deficits. • Temporal processing deficits result in suboptimal integration of multisensory cues. • Top-down processing may be a determining factor for speech-in-speech perception. [ABSTRACT FROM AUTHOR]

Everyday speech communication often occurs in environments with background noise, and the impact of noise on speech recognition can vary depending on factors such as noise type, noise intensity, and the listener's hearing ability. However, the extent to which neural mechanisms in speech understanding are influenced by different types and levels of noise remains unknown. This study aims to investigate whether individuals exhibit distinct neural responses and attention strategies depending on noise conditions. We recorded electroencephalography (EEG) data from 20 participants with normal hearing (13 males) and evaluated both neural tracking of speech envelopes and behavioral performance in speech understanding in the presence of varying types of background noise. Participants engaged in an EEG experiment consisting of two separate sessions. The first session involved listening to a 12-min story presented binaurally without any background noise. In the second session, speech understanding scores were measured using matrix sentences presented under speech-shaped noise (SSN) and Story noise background noise conditions at noise levels corresponding to sentence recognitions score (SRS). We observed differences in neural envelope correlation depending on noise type but not on its level. Interestingly, the impact of noise type on the variation in envelope tracking was more significant among participants with higher speech perception scores, while those with lower scores exhibited similarities in envelope correlation regardless of the noise condition. The findings suggest that even individuals with normal hearing could adopt different strategies to understand speech in challenging listening environments, depending on the type of noise., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2023 An, Lee, Suh and Lim.)

As people grow older, speech perception difficulties become highly prevalent, especially in noisy listening situations. Moreover, it is assumed that speech intelligibility is more affected in the event of background noises that induce a higher cognitive load, i.e., noises that result in informational versus energetic masking. There is ample evidence showing that speech perception problems in aging persons are partly due to hearing impairment and partly due to age-related declines in cognition and suprathreshold auditory processing. In order to develop effective rehabilitation strategies, it is indispensable to know how these different degrading factors act upon speech perception. This implies disentangling effects of hearing impairment versus age and examining the interplay between both factors in different background noises of everyday settings. To that end, we investigated open-set sentence identification in six participant groups: a young (20–30 years), middle-aged (50–60 years), and older cohort (70–80 years), each including persons who had normal audiometric thresholds up to at least 4 kHz, on the one hand, and persons who were diagnosed with elevated audiometric thresholds, on the other hand. All participants were screened for (mild) cognitive impairment. We applied stationary and amplitude modulated speech-weighted noise, which are two types of energetic maskers, and unintelligible speech, which causes informational masking in addition to energetic masking. By means of these different background noises, we could look into speech perception performance in listening situations with a low and high cognitive load, respectively. Our results indicate that, even when audiometric thresholds are within normal limits up to 4 kHz, irrespective of threshold elevations at higher frequencies, and there is no indication of even mild cognitive impairment, masked speech perception declines by middle age and decreases further on to older age. The impact of hearing impairment is as detrimental for young and middle-aged as it is for older adults. When the background noise becomes cognitively more demanding, there is a larger decline in speech perception, due to age or hearing impairment. Hearing impairment seems to be the main factor underlying speech perception problems in background noises that cause energetic masking. However, in the event of informational masking, which induces a higher cognitive load, age appears to explain a significant part of the communicative impairment as well. We suggest that the degrading effect of age is mediated by deficiencies in temporal processing and central executive functions. This study may contribute to the improvement of auditory rehabilitation programs aiming to prevent aging persons from missing out on conversations, which, in turn, will improve their quality of life. [ABSTRACT FROM AUTHOR]

A visual search for targets is facilitated when the target objects are on a different depth plane than other masking objects cluttering the scene. The ability of observers to determine whether one of four letters presented stereoscopically at four symmetrically located positions on the fixation plane differed from the other three was assessed when the target letters were masked by other randomly positioned and oriented letters appearing on the same depth plane as the target letters, or in front, or behind it. Three additional control maskers, derived from the letter maskers, were also presented on the same three depth planes: (1) random-phase maskers (same spectral amplitude composition as the letter masker but with the phase spectrum randomized); (2) random-pixel maskers (the locations of the letter maskers' pixel amplitudes were randomized); (3) letter-fragment maskers (the same letters as in the letter masker but broken up into fragments). Performance improved with target duration when the target-letter plane was in front of the letter-masker plane, but not when the target letters were on the same plane as the masker, or behind it. A comparison of the results for the four different kinds of maskers indicated that maskers consisting of recognizable objects (letters or letter fragments) interfere more with search and comparison judgments than do visual noise maskers having the same spatial frequency profile and contrast. In addition, performance was poorer for letter maskers than for letter-masker fragments, suggesting that the letter maskers interfered more with performance than the letter-fragment maskers because of the lexical activity they elicit. [ABSTRACT FROM AUTHOR]

Typically, understanding speech seems effortless and automatic. However, a variety of factors may, independently or interactively, make listening more effortful. Physiological measures may help to distinguish between the application of different cognitive mechanisms whose operation is perceived as effortful. In the present study, physiological and behavioral measures associated with task demand were collected along with behavioral measures of performance while participants listened to and repeated sentences. The goal was to measure psychophysiological reactivity associated with three degraded listening conditions, each of which differed in terms of the source of the difficulty (distortion, energetic masking, and informational masking), and therefore were expected to engage different cognitive mechanisms. These conditions were chosen to be matched for overall performance (keywords correct), and were compared to listening to unmasked speech produced by a natural voice. The three degraded conditions were: (1) Unmasked speech produced by a computer speech synthesizer, (2) Speech produced by a natural voice and masked by speech-shaped noise and (3) Speech produced by a natural voice and masked by two-talker babble. Masked conditions were both presented at a -8 dB signal to noise ratio (SNR), a level shown in previous research to result in comparable levels of performance for these stimuli and maskers. Performance was measured in terms of proportion of key words identified correctly, and task demand or effort was quantified subjectively by self-report. Measures of psychophysiological reactivity included electrodermal (skin conductance) response frequency and amplitude, blood pulse amplitude and pulse rate. Results suggest that the two masked conditions evoked stronger psychophysiological reactivity than did the two unmasked conditions even when behavioral measures of listening performance and listeners’ subjective perception of task demand were comparable across the three degraded conditions.

To recognize speech in a noisy auditory scene, listeners need to perceptually segregate the target talker's voice from other competing sounds (stream segregation). A number of studies have suggested that the attentional demands placed on listeners increase as the acoustic properties and informational content of the competing sounds become more similar to that of the target voice. Hence we would expect attentional demands to be considerably greater when speech is masked by speech than when it is masked by steady-state noise. To investigate the role of attentional mechanisms in the unmasking of speech sounds, event-related potentials (ERPs) were recorded to a syllable masked by noise or competing speech under both active (the participant was asked to respond when the syllable was presented) or passive (no response was required) listening conditions. The results showed that the long-latency auditory response to a syllable (/ bi /), presented at different signal-to-masker ratios (SMRs), was similar in both passive and active listening conditions, when the masker was a steady-state noise. In contrast, a switch from the passive listening condition to the active one, when the masker was two-talker speech, significantly enhanced the ERPs to the syllable. These results support the hypothesis that the need to engage attentional mechanisms in aid of scene analysis increases as the similarity (both acoustic and informational) between the target speech and the competing background sounds increases. [ABSTRACT FROM AUTHOR]

The present study examined to what extent proficiency in a non-native language influences speech perception in noise. We explored how English proficiency affected native (Swedish) and non-native (English) speech perception in four speech reception threshold (SRT) conditions including two energetic (stationary, fluctuating noise) and two informational (two-talker babble Swedish, two-talker babble English) maskers. Twenty-three normal-hearing native Swedish listeners participated, age between 28 and 64 years. The participants also performed standardized tests in English proficiency, non-verbal reasoning and working memory capacity. Our approach with focus on proficiency and the assessment of external as well as internal, listener-related factors allowed us to examine which variables explained intra-and interindividual differences in native and non-native speech perception performance. The main result was that in the non-native target, the level of English proficiency is a decisive factor for speech intelligibility in noise. High English proficiency improved performance in all four conditions when target language was English. The informational maskers were interfering more with perception than energetic maskers, specifically in the non-native language. The study also confirmed that the SRT's were better when target language was native compared to non-native.

The effects of two types of auditory distracters (steady-state noise vs. four-talker babble) on visual-only speechreading accuracy were tested against a baseline (silence) in 23 participants with above-average speechreading ability. Their task was to speechread high frequency Swedish words. They were asked to rate their own performance and effort, and report how distracting each type of auditory distracter was. Only four-talker babble impeded speechreading accuracy. This suggests competition for phonological processing, since the four-talker babble demands phonological processing, which is also required for the speechreading task. Better accuracy was associated with lower self-rated effort in silence; no other correlations were found.

Purpose: This study investigated the development of spatial release from masking in children using closed-set Mandarin disyllabic words and monosyllabic words carrying lexical tones as test stimuli and speech spectrum–weighted noise as a masker. Method: Twenty-six children ages 4–9 years and 12 adults, all with normal hearing, participated in speech recognition tests under 2 conditions: (a) speech and noise spatially mixed and presented from the front (NF), and (b) speech presented from the front with noise spatially separated and presented from the side (NS) with different signal-to-noise ratios (SNRs). Performance-SNR psychometric functions were obtained that generated the SNR for a 50% correct score (SNR-50%) as the outcome measure. Results: In the child participants, SNR-50% improved with age in NS but not NF. The difference in SNR-50% between NS and NF—the spatial release from masking (SRM)—increased with age with an average improvement of 0.1–0.15 dB per month. Conclusions: SRM has a long developmental time, at least up to 9 years of age, which is significantly longer than some previous developmental studies have suggested. The child participants had not yet reached the adult SRM performance level. SRM is a potential clinical measure to reflect the maturation of spatial auditory processing. [ABSTRACT FROM AUTHOR]

It is easier to recognize a masked speech when the speech and its masker are perceived as spatially segregated. Using event-related potentials, this study examined how the early cortical representation of speech is affected by different masker types and perceptual locations, when the listener is either passively or actively listening to the target speech syllable. The results showed that the two-talker-speech masker induced a much larger masking effect on the N1/P2 complex than either the steady-state-noise masker or the amplitude-modulated speech-spectrum-noise masker did. Also, a switch from the passive- to active-listening condition enhanced the N1/P2 complex only when the masker was speech. Moreover, under the active-listening condition, perceived separation between target and masker enhanced the N1/P2 complex only when the masker was speech. Thus, when a masker is present, the effect of selective attention to the target-speech signal on the early cortical representation of the speech signal is masker-type dependent. [ABSTRACT FROM AUTHOR]

The effects of two types of auditory distracters (steady-state noise vs. four-talker babble) on visual-only speechreading accuracy were tested against a baseline (silence) in 23 participants with above-average speechreading ability. Their task was to speechread high frequency Swedish words. They were asked to rate their own performance and effort, and report how distracting each type of auditory distracter was. Only four-talker babble impeded speechreading accuracy. This suggests competition for phonological processing, since the four-talker babble demands phonological processing, which is also required for the speechreading task. Better accuracy was associated with lower self-rated effort in silence; no other correlations were found. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigate how speakers can improve their segregation from a background noise. [•] Lombard speech is explored in realistic conditions (interactive game, loudspeakers). [•] Speakers maintain a positive SNR in noise and boost their energy around 3kHz. [•] They enhance the modulation of their speech in f 0 and intensity. [•] When possible, they specifically adjust f 0 and F1 to minima of the noise spectrum. [ABSTRACT FROM AUTHOR]

Nonspeech materials are widely used to identify basic mechanisms underlying speech perception. For instance, they have been used to examine the origin of compensation for coarticulation, the observation that listeners' categorization of phonetic segments depends on neighboring segments (Mann, 1980). Specifically, nonspeech precursors matched to critical formant frequencies of speech precursors have been shown to produce similar categorization shifts as speech contexts. This observation has been interpreted to mean that spectrally contrastive frequency relations between neighboring segments underlie the categorization shifts observed after speech, as well as nonspeech precursors (Lotto & Kluender, 1998). From the gestural perspective, however, categorization shifts in speech contexts occur because of listeners' sensitivity to acoustic information for coarticulatory gestural overlap in production; in nonspeech contexts, this occurs because of energetic masking of acoustic information for gestures. In 2 experiments, we distinguish the energetic masking and spectral contrast accounts. In Experiment 1, we investigated the effects of varying precursor tone frequency on speech categorization. Consistent only with the masking account, tonal effects were greater for frequencies close enough to those in the target syllables for masking to occur. In Experiment 2, we filtered the target stimuli to simulate effects of masking and obtained behavioral outcomes that closely resemble those with nonspeech tones. We conclude that masking provides the more plausible account of nonspeech context effects. More generally, we suggest that similar results from the use of speech and nonspeech materials do not automatically imply identical origins and that the use of nonspeech in speech studies entails careful examination of the nature of information in the nonspeech materials. [ABSTRACT FROM AUTHOR]

Subjective tinnitus patients experience more hearing difficulties than normal peers in complex hearing environments, even though most of these patients have normal pure-tone hearing thresholds. Using speech recognition tasks under different masking conditions can provide insight into whether the effects of tinnitus are lateralized and the mechanisms behind the effects. By simulating sound field recordings, we obtain a target speech sentence that can be perceived as presented on one side and noise or speech masking with or without spatial separation from it. Our study used the virtual sound field technique to investigate the difference in speech recognition ability between chronic subjective tinnitus patients and a normal-hearing control group under the four masking conditions (speech-spectrum noise masking or two-talker speech masking, with or without perceived spatial separation). Experiment 1 showed no differences for target speech perceived location (left or right), which rules out a lateralization of the effect of tinnitus patients. Experiment 2 further found that although tinnitus patients had weaker performance than normal people in very complex auditory scenarios, when the spatial cue of the target speech exists, they can make good use of this cue to make up for the original processing disadvantage and achieve a similar performance as the normal-hearing group. In addition, the current study distinguished the effects of informational masking and energetic masking on speech recognition in patients with tinnitus and normal hearing. The results suggest that the impact of tinnitus on speech recognition in patients is more likely to occur in the auditory center rather than the periphery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wang, Liu, Kong, Zhao, Diao and Ma.)

Background: In certain masking paradigms, the masker can have two components, energetic and informational. Energetic masking is the traditional peripheral masking, whereas informational masking involves confusions (uncertainty) between the signal and masker that originate more centrally in the auditory system. Sperry et al (1997) used Northwestern University Auditory Test No. 6 (NU-6) words in multitalker babble to study the differential effects of energetic and informational masking using babble played temporally forward (FB) and backward (BB). The FB and BB are the same except BB is void of the contextual and semantic content cues that are available in FB. It is these informational cues that are thought to fuel informational masking. Sperry et al found 15% better recognition performance (~3 dB) on BB than on FB, which can be interpreted as the presence of informational masking in the FB condition and not in the BB condition (Dirks and Bower, 1969). The Words-in-Noise Test (WIN) (Wilson, 2003; Wilson and McArdle, 2007) uses NU-6 words as the signal and multitalker babble as the masker, which is a combination of stimuli that potentially could produce informational masking. The WIN presents 5 or 10 words at each of seven signal-to-noise ratios (S/N, SNR) from 24 to 0 dB in 4 dB decrements with the 50% correct point being the metric of interest. The same recordings of the NU-6 words and multitalker babble used by Sperry et al are used in the WIN. Purpose: To determine whether informational masking was involved with the WIN. Research Design: Descriptive, quasi-experimental designs were conducted in three experiments using FB and BB in various paradigms in which FB and BB varied from 4.3 sec concatenated segments to essentially continuous. Study Sample: Eighty young adults with normal hearing and 64 older adults with sensorineural hearing losses participated in a series of three experiments. Data Collection and Analysis: Experiment 1 compared performance on the normal WIN (FB) with performance on the WIN in which the babble segment with each word was reversed temporally (BB). Experiment 2 examined the effects of continuous FB and BB segments on WIN performance. Experiment 3 replicated the Sperry et al (1997) experiment at 4 and 0 dB S/N using NU-6 words in the FB and BB conditions. Results: Experiment 1--with the WIN paradigm, recognition performances on FB and BB were the same for listeners with normal hearing and listeners with hearing loss, except at the 0 dB S/N with the listeners with normal hearing at which performance was significantly better on BB than FB. Experiment 2--recognition performances on FB and BB were the same at all SNRs for listeners with normal hearing using a slightly modified WIN paradigm. Experiment 3--there was no difference in performances on the FB and BB conditions with either of the two SNRs. Conclusions: Informational masking was not involved in the WIN paradigm. The Sperry et al results were not replicated, which is thought to be related to the way in which the Sperry et al BB condition was produced. [ABSTRACT FROM AUTHOR]

Visual cues are known to aid auditory processing when they provide direct information about signal content, as in lip reading. However, some studies hint that visual cues also aid auditory perception by guiding attention to the target in a mixture of similar sounds. The current study directly tests this idea for complex, nonspeech auditory signals, using a visual cue providing only timing information about the target. Listeners were asked to identify a target zebra finch bird song played at a random time within a longer, competing masker. Two different maskers were used: noise and a chorus of competing bird songs. On half of all trials, a visual cue indicated the timing of the target within the masker. For the noise masker, the visual cue did not affect performance when target and masker were from the same location, but improved performance when target and masker were in different locations. In contrast, for the chorus masker, visual cues improved performance only when target and masker were perceived as coming from the same direction. These results suggest that simple visual cues for when to listen improve target identification by enhancing sounds near the threshold of audibility when the target is energetically masked and by enhancing segregation when it is difficult to direct selective attention to the target. Visual cues help little when target and masker already differ in attributes that enable listeners to engage selective auditory attention effectively, including differences in spectrotemporal structure and in perceived location. [ABSTRACT FROM AUTHOR]

Abstract: Under conditions in the presence of competing talkers, presenting the early part of a target sentence in quiet improves recognition of the last keyword of the sentence. This content-priming effect depends on a working-memory resource holding the information of the early presented part of the target speech (the content prime). Older adults usually exhibit declined working memory and experience more difficulties in speech recognition under “cocktail-party” conditions. This study investigated whether speech masking also affects recall of the content prime and whether the content-priming effect declines in older adults. The results show that in both younger adults and older adults, although the content prime was heard in quiet, recall of keywords in the prime was significantly affected by the signal-to-masker ratio of the target/masker presentation. The vulnerability of prime recall to speech masking was larger in older adults than that in younger adults. Also, the content-priming effect disappeared in older adults, even though older adults are able to use the content prime to determine the target speech in the presence of competing talkers. Thus, a speech masker affects not only recognition but also recall of speech, and there is an age-related decline in both content-priming-based unmasking of the target speech and recall of the prime. [Copyright &y& Elsevier]