Speech Maskers Research Articles

The Effects of Dynamic-range Automatic Gain Control on Sentence Intelligibility With a Speech Masker in Simulated Cochlear Implant Listening.

"Channel-linked" and "multi-band" front-end automatic gain control (AGC) were examined as alternatives to single-band, channel-unlinked AGC in simulated bilateral cochlear implant (CI) processing. In channel-linked AGC, the same gain control signal was applied to the input signals to both of the two CIs ("channels"). In multi-band AGC, gain control acted independently on each of a number of narrow frequency regions per channel. Speech intelligibility performance was measured with a single target (to the left, at -15 or -30°) and a single, symmetrically-opposed masker (to the right) at a signal-to-noise ratio (SNR) of -2 decibels. Binaural sentence intelligibility was measured as a function of whether channel linking was present and of the number of AGC bands. Analysis of variance was performed to assess condition effects on percent correct across the two spatial arrangements, both at a high and a low AGC threshold. Acoustic analysis was conducted to compare postcompressed better-ear SNR, interaural differences, and monaural within-band envelope levels across processing conditions. Analyses of variance indicated significant main effects of both channel linking and number of bands at low threshold, and of channel linking at high threshold. These improvements were accompanied by several acoustic changes. Linked AGC produced a more favorable better-ear SNR and better preserved broadband interaural level difference statistics, but did not reduce dynamic range as much as unlinked AGC. Multi-band AGC sometimes improved better-ear SNR statistics and always improved broadband interaural level difference statistics whenever the AGC channels were unlinked. Multi-band AGC produced output envelope levels that were higher than single-band AGC. These results favor strategies that incorporate channel-linked AGC and multi-band AGC for bilateral CIs. Linked AGC aids speech intelligibility in spatially separated speech, but reduces the degree to which dynamic range is compressed. Combining multi-band and channel-linked AGC offsets the potential impact of diminished dynamic range with linked AGC without sacrificing the intelligibility gains observed with linked AGC.

The effects of auditory spatial training on informational masking release in elderly listeners: a study protocol for a randomized clinical trial

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 25th February 2019.

Effects of Adaptive Hearing Aid Directionality and Noise Reduction on Masked Speech Recognition for Children Who Are Hard of Hearing.

Purpose The purpose of this study was to evaluate speech-in-noise and speech-in-speech recognition associated with activation of a fully adaptive directional hearing aid algorithm in children with mild to severe bilateral sensory/neural hearing loss. Method Fourteen children (5-14 years old) who are hard of hearing participated in this study. Participants wore laboratory hearing aids. Open-set word recognition thresholds were measured adaptively for 2 hearing aid settings: (a) omnidirectional (OMNI) and (b) fully adaptive directionality. Each hearing aid setting was evaluated in 3 listening conditions. Fourteen children with normal hearing served as age-matched controls. Results Children who are hard of hearing required a more advantageous signal-to-noise ratio than children with normal hearing to achieve comparable performance in all 3 conditions. For children who are hard of hearing, the average improvement in signal-to-noise ratio when comparing fully adaptive directionality to OMNI was 4.0 dB in noise, regardless of target location. Children performed similarly with fully adaptive directionality and OMNI settings in the presence of the speech maskers. Conclusions Compared to OMNI, fully adaptive directionality improved speech recognition in steady noise for children who are hard of hearing, even when they were not facing the target source. This algorithm did not affect speech recognition when the background noise was speech. Although the use of hearing aids with fully adaptive directionality is not proposed as a substitute for remote microphone systems, it appears to offer several advantages over fixed directionality, because it does not depend on children facing the target talker and provides access to multiple talkers within the environment. Additional experiments are required to further evaluate children's performance under a variety of spatial configurations in the presence of both noise and speech maskers.

Informational masking of speech analogues by intelligible and non-intelligible but acoustically similar interferers

Informational masking of target speech is generally greater when the interfering speech is intelligible than when it is not (e.g., speech from an unfamiliar language), but the relative contributions of acoustic-phonetic and linguistic interference are often difficult to assess owing to acoustic differences between interferers (e.g., different talkers). This study used three-formant analogues (F1 + F2 + F3) of natural sentences as targets and interferers. Target formants were presented monaurally (F0 = 120.3 Hz) either alone or accompanied with the contralateral ear by interfering formants from another sentence (F0 = 151.5 Hz); a target-to-masker ratio (TMR) between ears of 0, 6, or 12 dB was used. Interferers were either intelligible or rendered non-intelligible by delaying F2 and advancing F3 by 150 ms relative to F1, a manipulation designed to minimize spectro-temporal differences between corresponding interferers. Target-sentence intelligibility (keywords correct) was 67% when presented alone but fell considerably when a non-intelligible interferer was present (49%) and significantly further when the interferer was intelligible (41%). The changes in TMR produced neither a significant main effect nor an interaction with interferer type. The results suggest that although linguistic factors contribute to informational masking, interference with acoustic-phonetic processing of the target can explain much of the impact on intelligibility. [Work supported by ESRC.]

Factors affecting speech-in-noise and speech-in-speech recognition for school-age children with hearing loss

Children with hearing loss require a more advantageous SNR than children with normal hearing to achieve comparable masked speech recognition performance. Although children with hearing loss continue to have difficulties even when appropriately fitted with hearing aids, individual differences are often substantial. This study evaluated the influence of age, degree of hearing loss, aided audibility, and daily hearing aid use on speech-in-noise and speech-in-speech recognition on a sample of 47 children (5-17 years) with bilateral, sensorineural hearing loss. Age-matched children with normal hearing were also tested. Each child completed open-set monosyllabic word recognition in two masker conditions; speech-shaped noise and two-talker speech. Thresholds for 50% correct were measured in each masker using an adaptive tracking procedure. Compared to children with normal hearing, thresholds for children with hearing loss were elevated by an average of 7.4 dB in the noise masker and 6.5 dB in the speech masker. Preliminary results indicate that both age and aided audibility were significant predictors of performance for children with hearing loss in both masker conditions. Hearing aid use was a significant predictor of performance in noise. Degree of hearing loss was not associated with performance in either masker when aided audibility was taken into account.

Listening while balancing: Dual-task costs in speech vs. noise maskers

Many middle-aged adults report that listening is effortful in adverse communication situations. One means of quantifying listening effort is by measuring dual-task costs. The present study examined the influence of early aging on dual-task costs using a technique which required participants (younger and middle-aged adults) to complete a postural control task while listening to speech. For the postural control task, participants stood on a force platform and had to maintain their center of pressure within a prescribed area (denoted using real-time visual feedback). Two speech perception tasks were used, each presented with two types of maskers (same-sex two-talker speech masker and steady-state speech-shaped noise): repeating back low-predictability sentences, and listening to Connected Speech Test passages and then answering content questions based on each passage. This presentation will describe data analyses designed to uncover how listener age group and masker type influenced listening effort as measured by dual-task costs. [Work supported by NIDCD 012057.]

Auditory–visual integration during nonconscious perception

Our study proposes a test of a key assumption of the most prominent model of consciousness – the global workspace (GWS) model (e.g., Baars, 2002, 2005, 2007; Dehaene & Naccache, 2001; Mudrik, Faivre, & Koch, 2014). This assumption is that multimodal integration requires consciousness; however, few studies have explicitly tested if integration can occur between nonconscious information from different modalities. The proposed study examined whether a classic indicator of multimodal integration – the McGurk effect – can be elicited with subliminal auditory–visual speech stimuli. We used a masked speech priming paradigm developed by Kouider and Dupoux (2005) in conjunction with continuous flash suppression (CFS; Tsuchiya & Koch, 2005), a binocular rivalry technique for presenting video stimuli subliminally. Applying these techniques together, we carried out two experiments in which participants categorised auditory syllable targets which were preceded by subliminal auditory–visual (AV) speech primes. Subliminal AV primes were either illusion-inducing (McGurk) or illusion-neutral (Incongruent) combinations of speech stimuli. In Experiment 1, the categorisation of the syllable target (“pa”) was facilitated by the same syllable prime when it was part of a McGurk combination (auditory “pa” and visual “ka”) but not when part of an Incongruent combination (auditory “pa” and visual “wa”). This dependency on specific AV combinations indicated a nonconscious AV interaction. Experiment 2 presented a different syllable target (“ta”) which matched the predicted illusory outcome of the McGurk combination – here, both the McGurk combination (auditory “pa” and visual “ka”) and the Incongruent combination (auditory “ta” and visual “ka”) failed to facilitate target categorisation. The combined results of both Experiments demonstrate a type of nonconscious multimodal interaction that is distinct from integration – it allows unimodal information that is compatible for integration (i.e., McGurk combinations) to persist and influence later processes, but does not actually combine and alter that information. As the GWS model does not account for non-integrative multimodal interactions, this places some pressure on such models of consciousness.

A method for degrading sound localization while preserving binaural advantages for speech reception in noise.

This study developed and tested a real-time processing algorithm designed to degrade sound localization (LocDeg algorithm) without affecting binaural benefits for speech reception in noise. Input signals were divided into eight frequency channels. The odd-numbered channels were mixed between the ears to confuse the direction of interaural cues while preserving interaural cues in the even-numbered channels. The LocDeg algorithm was evaluated for normal-hearing listeners performing sound localization and speech-reception tasks. Results showed that the LocDeg algorithm successfully degraded sound-localization performance without affecting speech-reception performance or spatial release from masking for speech in noise. The LocDeg algorithm did, however, degrade speech-reception performance in a task involving spatially separated talkers in a multi-talker environment, which is thought to depend on differences in perceived spatial location of concurrent talkers. This LocDeg algorithm could be a valuable tool for isolating the importance of sound-localization ability from other binaural benefits in real-world environments.

Error patterns of native and non-native listeners' perception of speech in noise.

Speech perception in noise requires both bottom-up sampling of the stimulus and top-down reconstruction of the masked signal from a language model. Previous studies have provided mixed evidence about the exact role that linguistic knowledge plays in native and non-native listeners' perception of masked speech. This paper describes an analysis of whole utterance, content word, and morphosyntactic error patterns to test the prediction that non-native listeners are uniquely affected by energetic and informational masks because of limited information at multiple linguistic levels. The results reveal a consistent disadvantage for non-native listeners at all three levels in challenging listening environments.

Effect of F0 contour on perception of Mandarin Chinese speech against masking.

Intonation has many perceptually significant functions in language that contribute to speech recognition. This study aims to investigate whether intonation cues affect the unmasking of Mandarin Chinese speech in the presence of interfering sounds. Specifically, intelligibility of multi-tone Mandarin Chinese sentences with maskers consisting of either two-talker speech or steady-state noise was measured in three (flattened, typical, and exaggerated) intonation conditions. Different from most of the previous studies, the present study only manipulate and modify the intonation information but preserve tone information. The results showed that recognition of the final keywords in multi-tone Mandarin Chinese sentences was much better under the original F0 contour condition than the decreased F0 contour or exaggerated F0 contour conditions whenever there was a noise or speech masker, and an exaggerated F0 contour reduced the intelligibility of Mandarin Chinese more under the speech masker condition than that under the noise masker condition. These results suggested that speech in a tone language (Mandarin Chinese) is harder to understand when the intonation is unnatural, even if the tone information is preserved, and an unnatural intonation contour decreases releasing Mandarin Chinese speech from masking, especially in a multi-person talking environment.

Masked Sentence Recognition in Children, Young Adults, and Older Adults: Age-Dependent Effects of Semantic Context and Masker Type.

Masked speech recognition in normal-hearing listeners depends in part on masker type and semantic context of the target. Children and older adults are more susceptible to masking than young adults, particularly when the masker is speech. Semantic context has been shown to facilitate noise-masked sentence recognition in all age groups, but it is not known whether age affects a listener's ability to use context with a speech masker. The purpose of the present study was to evaluate the effect of masker type and semantic context of the target as a function of listener age. Listeners were children (5 to 16 years), young adults (19 to 30 years), and older adults (67 to 81 years), all with normal or near-normal hearing. Maskers were either speech-shaped noise or two-talker speech, and targets were either semantically correct (high context) sentences or semantically anomalous (low context) sentences. As predicted, speech reception thresholds were lower for young adults than either children or older adults. Age effects were larger for the two-talker masker than the speech-shaped noise masker, and the effect of masker type was larger in children than older adults. Performance tended to be better for targets with high than low semantic context, but this benefit depended on age group and masker type. In contrast to adults, children benefitted less from context in the two-talker speech masker than the speech-shaped noise masker. Context effects were small compared with differences across age and masker type. Different effects of masker type and target context are observed at different points across the lifespan. While the two-talker masker is particularly challenging for children and older adults, the speech masker may limit the use of semantic context in children but not adults.

Mechanisms of Localization and Speech Perception with Colocated and Spatially Separated Noise and Speech Maskers Under Single-Sided Deafness with a Cochlear Implant.

This study tested listeners with a cochlear implant (CI) in one ear and acoustic hearing in the other ear, to assess their ability to localize sound and to understand speech in collocated or spatially separated noise or speech maskers. Eight CI listeners with contralateral acoustic hearing ranging from normal hearing to moderate sensorineural hearing loss were tested. Localization accuracy was measured in five of the listeners using stimuli that emphasized the separate contributions of interaural level differences (ILDs) and interaural time differences (ITD) in the temporal envelope and/or fine structure. Sentence recognition was tested in all eight CI listeners, using collocated and spatially separated speech-shaped Gaussian noise and two-talker babble. Performance was compared with that of age-matched normal-hearing listeners via loudspeakers or via headphones with vocoder simulations of CI processing. Localization improved with the CI but only when high-frequency ILDs were available. Listeners experienced no additional benefit via ITDs in the stimulus envelope or fine structure using real or vocoder-simulated CIs. Speech recognition in two-talker babble improved with a CI in seven of the eight listeners when the target was located at the front and the babble was presented on the side of the acoustic-hearing ear, but otherwise showed little or no benefit of a CI. Sound localization can be improved with a CI in cases of significant residual hearing in the contralateral ear, but only for sounds with high-frequency content, and only based on ILDs. In speech understanding, the CI contributed most when it was in the ear with the better signal to noise ratio with a speech masker.

Spatial Release From Masking Using Clinical Corpora: Sentence Recognition In a Colocated or Spatially Separated Speech Masker

Background: Speech recognition in complex multisource environments is challenging, particularly forlisteners with hearing loss. One source of difficulty is the reduced ability of listeners with hearing loss tobenefit from spatial separation of the target and masker, an effect called spatial release from masking(SRM). Despite the prevalence of complex multisource environments in everyday life, SRM is not routinelyevaluated in the audiology clinic.<br />Purpose: The purpose of this study was to demonstrate the feasibility of assessing SRM in adults usingwidely available tests of speech-in-speech recognition that can be conducted using standard clinicalequipment.<br />Research Design: Participants were 22 young adults with normal hearing. The task was masked sentencerecognition, using each of five clinically available corpora with speech maskers. The target alwayssounded like it originated from directly in front of the listener, and the masker either sounded like it originatedfrom the front (colocated with the target) or from the side (separated from the target). In the realspatial manipulation conditions, source location was manipulated by routing the target and masker toeither a single speaker or to two speakers: one directly in front of the participant, and one mountedin an adjacent corner, 90° to the right. In the perceived spatial separation conditions, the target andmasker were presented from both speakers with delays that made them sound as if they were eithercolocated or separated.<br />Results: With real spatial manipulations, the mean SRM ranged from 7.1 to 11.4 dB, depending on thespeech corpus. With perceived spatial manipulations, the mean SRM ranged from 1.8 to 3.1 dB. Whereasreal separation improves the signal-to-noise ratio in the ear contralateral to the masker, SRM in the perceivedspatial separation conditions is based solely on interaural timing cues.<br />Conclusions: The finding of robust SRM with widely available speech corpora supports the feasibility ofmeasuring this important aspect of hearing in the audiology clinic. The finding of a small but significantSRM in the perceived spatial separation conditions suggests that modified materials could be used toevaluate the use of interaural timing cues specifically.<br />

Effects of Acquired Aphasia on the Recognition of Speech Under Energetic and Informational Masking Conditions.

Persons with aphasia (PWA) often report difficulty understanding spoken language in noisy environments that require listeners to identify and selectively attend to target speech while ignoring competing background sounds or “maskers.” This study compared the performance of PWA and age-matched healthy controls (HC) on a masked speech identification task and examined the consequences of different types of masking on performance. Twelve PWA and 12 age-matched HC completed a speech identification task comprising three conditions designed to differentiate between the effects of energetic and informational masking on receptive speech processing. The target and masker speech materials were taken from a closed-set matrix-style corpus, and a forced-choice word identification task was used. Target and maskers were spatially separated from one another in order to simulate real-world listening environments and allow listeners to make use of binaural cues for source segregation. Individualized frequency-specific gain was applied to compensate for the effects of hearing loss. Although both groups showed similar susceptibility to the effects of energetic masking, PWA were more susceptible than age-matched HC to the effects of informational masking. Results indicate that this increased susceptibility cannot be attributed to age, hearing loss, or comprehension deficits and is therefore a consequence of acquired cognitive-linguistic impairments associated with aphasia. This finding suggests that aphasia may result in increased difficulty segregating target speech from masker speech, which in turn may have implications for the ability of PWA to comprehend target speech in multitalker environments, such as restaurants, family gatherings, and other everyday situations.

Determining the energetic and informational components of speech-on-speech masking in listeners with sensorineural hearing loss.

The ability to identify the words spoken by one talker masked by two or four competing talkers was tested in young-adult listeners with sensorineural hearing loss (SNHL). In a reference/baseline condition, masking speech was colocated with target speech, target and masker talkers were female, and the masker was intelligible. Three comparison conditions included replacing female masker talkers with males, time-reversal of masker speech, and spatial separation of sources. All three variables produced significant release from masking. To emulate energetic masking (EM), stimuli were subjected to ideal time-frequency segregation retaining only the time-frequency units where target energy exceeded masker energy. Subjects were then tested with these resynthesized "glimpsed stimuli." For either two or four maskers, thresholds only varied about 3 dB across conditions suggesting that EM was roughly equal. Compared to normal-hearing listeners from an earlier study [Kidd, Mason, Swaminathan, Roverud, Clayton, and Best, J. Acoust. Soc. Am. 140, 132-144 (2016)], SNHL listeners demonstrated both greater energetic and informational masking as well as higher glimpsed thresholds. Individual differences were correlated across masking release conditions suggesting that listeners could be categorized according to their general ability to solve the task. Overall, both peripheral and central factors appear to contribute to the higher thresholds for SNHL listeners.

Does the semantic content or syntactic regularity of masker speech affect speech-on-speech recognition?

Speech-on-speech recognition differs substantially across stimuli, but it is unclear what role linguistic features of the masker play in this variability. The linguistic similarity hypothesis suggests similarity between sentence-level semantic content of the target and masker speech increases masking. Sentence recognition in a two-talker masker was evaluated with respect to semantic content and syntactic structure of the masker (experiment 1) and linguistic similarity of the target and masker (experiment 2). Target and masker sentences were semantically meaningful or anomalous. Masker syntax was varied or the same across sentences. When other linguistic features of the masker were controlled, variability in syntactic structure across masker tokens was only relevant when the masker was played continuously (as opposed to gated); when played continuously, sentence-recognition thresholds were poorer with variable than consistent masker syntax, but this effect was small (0.5 dB). When the syntactic structure of the masker was held constant, semantic meaningfulness of the masker did not increase masking, and at times performance was better for the meaningful than the anomalous masker. These data indicate that sentence-level semantic content of the masker speech does not influence speech-on-speech masking. Further, no evidence that similarities between target/masker sentence-level semantic content increases masking was found.

Restoration and Efficiency of the Neural Processing of Continuous Speech Are Promoted by Prior Knowledge.

Sufficiently noisy listening conditions can completely mask the acoustic signal of significant parts of a sentence, and yet listeners may still report the perception of hearing the masked speech. This occurs even when the speech signal is removed entirely, if the gap is filled with stationary noise, a phenomenon known as perceptual restoration. At the neural level, however, it is unclear the extent to which the neural representation of missing extended speech sequences is similar to the dynamic neural representation of ordinary continuous speech. Using auditory magnetoencephalography (MEG), we show that stimulus reconstruction, a technique developed for use with neural representations of ordinary speech, works also for the missing speech segments replaced by noise, even when spanning several phonemes and words. The reconstruction fidelity of the missing speech, up to 25% of what would be attained if present, depends however on listeners’ familiarity with the missing segment. This same familiarity also speeds up the most prominent stage of the cortical processing of ordinary speech by approximately 5 ms. Both effects disappear when listeners have no or little prior experience with the speech segment. The results are consistent with adaptive expectation mechanisms that consolidate detailed representations about speech sounds as identifiable factors assisting automatic restoration over ecologically relevant timescales.

On Dynamic Pitch Benefit for Speech Recognition in Speech Masker.

Previous work demonstrated that dynamic pitch (i.e., pitch variation in speech) aids speech recognition in various types of noises. While this finding suggests dynamic pitch enhancement in target speech can benefit speech recognition in noise, it is of importance to know what noise characteristics affect dynamic pitch benefit, and who will benefit from enhanced dynamic pitch cues. Following our recent finding that temporal modulation in noise influences dynamic pitch benefit, we examined the effect of speech masker characteristics on dynamic pitch benefit. Specifically, the first goal of the study was to test the hypothesis that dynamic pitch benefit varies depending on the availability of pitch cues in the masker and the intelligibility of masker. The second goal of this study was to investigate whether older listeners as a group can benefit from dynamic pitch for speech recognition in speech maskers. In addition, individual factors of hearing loss and working memory capacity were examined for their impact on older listeners' dynamic pitch benefit. Twenty-three younger listeners with normal hearing and 37 older listeners with varying levels of hearing sensitivity participated the study, in which speech reception thresholds were measured with sentences in speech maskers. While we did not find an effect of masker characteristics on dynamic pitch benefit, the results showed older listeners can benefit from dynamic pitch for recognizing speech in speech maskers. The data also suggest that among those older listeners with hearing loss, dynamic pitch benefit is stronger for individuals with higher working memory capacity. This can be attributed to their ability to exploit facilitated lexical access in processing of degraded speech signal.

Age-Related Differences in the Effects of Masker Cuing on Releasing Chinese Speech From Informational Masking

The aims of the present study were to examine whether familiarity with a masker improves word recognition in speech masking situations and whether there are age-related differences in the effects of masker cuing. Thirty-two older listeners (range = 59–74; mean age = 66.41 years) with high-frequency hearing loss and 32 younger normal-hearing listeners (range = 21–28; mean age = 23.73) participated in this study, all of whom spoke Chinese as their first language. Two experiments were conducted and 16 younger and 16 older listeners were used in each experiment. The masking speech with different content from target speech with syntactically correct but semantically meaningless was a continuous recording of meaningless Chinese sentences spoken by two talkers. The masker level was adjusted to produce signal-to-masker ratios of -12, -8, -4, and 0 dB for the younger participants and -8, -4, 0, and 4 dB for the older participants. Under masker-priming conditions, a priming sentence, spoken by the masker talkers, was presented in quiet three times before a target sentence was presented together with a masker sentence 4 s later. In Experiment 1, using same-sentence masker-priming (identical to the masker sentence), the masker-priming improved the identification of the target sentence for both age groups compared to when no priming was provided. However, the amount of masking release was less in the older adults than in the younger adults. In Experiment 2, two kinds of primes were considered: same-sentence masker-priming, and different-sentence masker-priming (different from the masker sentence in content for each keyword). The results of Experiment 2 showed that both kinds of primes improved the identification of the targets for both age groups. However, the release from speech masking in both priming conditions was less in the older adults than in the younger adults, and the release from speech masking in both age groups was greater with same-sentence masker-priming than with different-sentence masker-priming. These results suggest that both the voice and content cues of a masker could be used to release target speech from maskers in noisy listening conditions. Furthermore, there was an age-related decline in masker-priming-induced release from speech masking.

Developmental Effects in Masking Release for Speech-in-Speech Perception Due to a Target/Masker Sex Mismatch.

The purpose of this study was to evaluate the extent to which infants, school-age children, and adults benefit from a target/masker sex mismatch in the context of speech detection or recognition in a background of 2 competing talkers. It was hypothesized that the ability to benefit from a target/masker sex mismatch develops between infancy and the early school-age years, as children gain listening experience in multi-talker environments. Listeners were infants (7 to 13 months), children (5 to 10 years), and adults (18 to 33 years) with normal hearing. A series of five experiments compared speech detection or recognition in continuous two-talker speech across target/masker conditions that were sex matched or sex mismatched. In experiments 1 and 2, an observer-based, single-interval procedure was used to estimate speech detection thresholds for a spondaic word in a two-talker speech masker. In experiments 3 and 4, speech recognition thresholds were estimated in continuous two-talker speech using a four-alternative, forced-choice procedure. In experiment 5, speech reception thresholds (SRTs) were estimated for adults using the forced-choice recognition procedure after ideal time-frequency segregation processing was applied to the stimuli. Speech detection thresholds for adults tested in experiments 1 and 2 were significantly higher when the target word and speech masker were matched in sex than when they were mismatched, but thresholds for infants were similar across sex-matched and sex-mismatched conditions. Results for experiments 3 and 4 showed that school-age children and adults benefit from a target/masker sex mismatch for a forced-choice word recognition task. Children, however, obtained greater benefit than adults in 1 condition, perhaps due to greater susceptibility to masking overall. In experiment 5, adults had substantial threshold reductions and more uniform performance across the 4 conditions evaluated in experiments 3 and 4 after the application of ideal time-frequency segregation to the stimuli. The pattern of results observed across experiments suggests that the ability to take advantage of differences in vocal characteristics typically found between speech produced by male and female talkers develops between infancy and the school-age years. Considerable child-adult differences in susceptibility to speech-in-speech masking were observed for school-age children as old as 11 years of age in both sex-matched and sex-mismatched conditions.