Two-talker Speech Research Articles

Age-Related Differences in the Effects of Linguistic and Nonlinguistic Masking on Semantic Processing: Evidence From the N400 Component in Young and Middle-Aged Listeners.

The purpose of this study was to determine if there are age-related differences in semantic processing with linguistic and nonlinguistic masking, as measured by the N400. Sixteen young (19-31 years) and 16 middle-aged (41-57 years) adults with relatively normal hearing sensitivity were asked to determine whether word pairs were semantically related or unrelated in three listening conditions: quiet, forward, and reverse two-talker speech competition at 0 dB SNR. Behavioral data (accuracies and reaction times) and auditory event-related potential data (N400 amplitudes and latencies) were analyzed using separate mixed design multivariate analysis of variances. Mean N400 amplitudes for semantically related word pairs were similar between young and middle-aged adults. Although neither group showed N400 amplitude differences between masker types, N400 amplitude was significantly greater in the presence of linguistic and nonlinguistic masking than in quiet. In contrast, mean N400 amplitudes for semantically unrelated words were significantly more negative for young adults and not significantly different among listening conditions. Our findings illustrated age-related differences during a semantic processing task, as indexed by the N400, that may not be evident in suprathreshold speech repetition/recognition tasks or behavioral data. Additionally, N400 amplitudes indicated that linguistic masking effects were equivalent to nonlinguistic masking effects on semantic processing.

Talker change detection by listeners varying in age and hearing loss.

Despite a vast literature on how speech intelligibility is affected by hearing loss and advanced age, remarkably little is known about the perception of talker-related information in these populations. Here, we assessed the ability of listeners to detect whether a change in talker occurred while listening to and identifying sentence-length sequences of words. Participants were recruited in four groups that differed in their age (younger/older) and hearing status (normal/impaired). The task was conducted in quiet or in a background of same-sex two-talker speech babble. We found that age and hearing loss had detrimental effects on talker change detection, in addition to their expected effects on word recognition. We also found subtle differences in the effects of age and hearing loss for trials in which the talker changed vs trials in which the talker did not change. These findings suggest that part of the difficulty encountered by older listeners, and by listeners with hearing loss, when communicating in group situations, may be due to a reduced ability to identify and discriminate between the participants in the conversation.

Children's use of spatial and visual cues for release from perceptual masking.

This study examined the role of visual speech in providing release from perceptual masking in children by comparing visual speech benefit across conditions with and without a spatial separation cue. Auditory-only and audiovisual speech recognition thresholds in a two-talker speech masker were obtained from 21 children with typical hearing (7-9 years of age) using a color-number identification task. The target was presented from a loudspeaker at 0° azimuth. Masker source location varied across conditions. In the spatially collocated condition, the masker was also presented from the loudspeaker at 0° azimuth. In the spatially separated condition, the masker was presented from the loudspeaker at 0° azimuth and a loudspeaker at -90° azimuth, with the signal from the -90° loudspeaker leading the signal from the 0° loudspeaker by 4 ms. The visual stimulus (static image or video of the target talker) was presented at 0° azimuth. Children achieved better thresholds when the spatial cue was provided and when the visual cue was provided. Visual and spatial cue benefit did not differ significantly depending on the presence of the other cue. Additional studies are needed to characterize how children's preferential use of visual and spatial cues varies depending on the strength of each cue.

Predicting speech-in-speech recognition: Short-term audibility and spatial separation.

Quantifying the factors that predict variability in speech-in-speech recognition represents a fundamental challenge in auditory science. Stimulus factors associated with energetic and informational masking (IM) modulate variability in speech-in-speech recognition, but energetic effects can be difficult to estimate in spectro-temporally dynamic speech maskers. The current experiment characterized the effects of short-term audibility and differences in target and masker location (or perceived location) on the horizontal plane for sentence recognition in two-talker speech. Thirty young adults with normal hearing (NH) participated. Speech reception thresholds and keyword recognition at a fixed signal-to-noise ratio (SNR) were measured in each spatial condition. Short-term audibility for each keyword was quantified using a glimpsing model. Results revealed that speech-in-speech recognition depended on the proportion of audible glimpses available in the target + masker keyword stimulus in each spatial condition, even across stimuli presented at a fixed global SNR. Short-term audibility requirements were greater for colocated than spatially separated speech-in-speech recognition, and keyword recognition improved more rapidly as a function of increases in target audibility with spatial separation. Results indicate that spatial cues enhance glimpsing efficiency in competing speech for young adults with NH and provide a quantitative framework for estimating IM for speech-in-speech recognition in different spatial configurations.

The Children’s English/Spanish Speech Recognition Test (ChEgSS): Feasibility, Reliability, and Normative data

The Children’s English/Spanish Speech Recognition Test (ChEgSS) is a computer-based tool for assessing closed-set word recognition in either speech-shaped noise or two-talker speech. Instructions and stimuli are recorded in both languages, and listeners respond by pointing to the picture depicting the word that they heard. Preliminary clinical feasibility and reliability data will be presented, along with age norms for children (4.1–17.0 yrs) who are either English monolinguals (n = 89) or Spanish/English bilinguals (n = 83). Results obtained with the two maskers will be evaluated with respect to age, language group, and receptive vocabulary. SRTs in English were higher in two-talker speech than speech-shaped noise and were 1.7dB lower for monolinguals than bilinguals for both maskers. SRTs were lower in English than Spanish for bilinguals in noise but not significantly different in speech. Consistent with prior research, SRTs in both languages improved with age; effects of age were more pronounced and prolonged in two-talker speech than in speech-shaped noise. The mean discrepancy between replicate estimates of SRT in English were 1.8 dB in noise and 3.1 in two-talker speech. Overall, these results suggest ChEgSS may be a valuable tool for clinical assessment of masked speech perception in children.

Comparing the effects of target and masker voice familiarity on children’s speech-in-speech recognition

Familiarity with a target voice has been shown to aid spoken word recognition for both children and adults. Familiarity effects of a target voice are not well understood, and even less is known about the impacts of masker voice familiarity. The present study investigated long-term target and masker voice familiarity effects on children’s speech-in-speech recognition by using the child’s own mother’s voice as stimuli. Open-set sentence recognition thresholds (SRTs) were measured adaptively in a two-talker speech masker. Twenty children were tested in three conditions, hearing their mother’s voice and two unfamiliar female voices: (1) Familiar Target/Unfamiliar Masker; (2) Familiar Masker/Unfamiliar Target; and (3) Unfamiliar Target/Unfamiliar Masker. Condition 1 measured effects of target familiarity; Condition 2 examined effects of masker familiarity; Condition 3 served as baseline. Results showed SRTs were significantly better when target speech was spoken by a familiar talker (the mother). When background speech was spoken by the familiar talker, performance was worse relative to an unfamiliar masker. This suggests that children do benefit from long-term voice familiarity with the target but not the masker speech. Thus, voice familiarity may impact children’s ability to attend to the target speech but does not always improve segregation.

Building on the Academic Legacy of Pat Stelmachowicz and other Pioneers in Developmental Psychoacoustics and Pediatric Audiology: The Children's English/Spanish Speech Recognition Test (ChEgSS).

Basic research investigating auditory development often has implications for clinical diagnosis and treatment of hearing loss in children, but it can be challenging to translate those findings into practice. Meeting that challenge was a guiding principle of Pat Stelmachowicz's research and mentorship. Her example inspired many of us to pursue translational research and motivated the recent development of the Children's English/Spanish Speech Recognition Test (ChEgSS). This test evaluates word recognition in noise or two-talker speech, with target and masker speech produced in either English or Spanish. The test uses recorded materials and a forced-choice response, so the tester need not be fluent in the test language. ChEgSS provides a clinical measure of masked speech recognition outcomes for children who speak English, Spanish, or both, including estimates of performance in noise and two-talker speech, with the goal of maximizing speech and hearing outcomes for children with hearing loss. This article highlights several of Pat's many contributions to pediatric hearing research and describes the motivation and development of ChEgSS.

The effects of face masks on speech-in-speech recognition for children and adults

Objectives: This study explored the effects of different face masks on school-age children’s and young adults’ word recognition. Design: Speech recognition thresholds were measured adaptively in a two-talker speech masker using a closed-set picture pointing task. Target words were recorded by a female talker in five conditions: no mask, transparent mask, face shield, N95 mask and surgical mask. Study samples: Thirty children (8–12 years) and 25 adults (18–25 years) with normal hearing. Results: Both children’s and adults’ word recognition was most negatively impacted by the face shield. Children’s recognition was also impaired by the transparent mask. No negative effects were observed for the N95 or surgical mask for either age group. Conclusion: School-age children, like young adults, are negatively affected by face masks when recognising speech in a two-talker speech masker, but the effects depend on the type of face mask being worn. Acoustic analyses suggest that the reflective materials used for masks impact speech signal quality and impair word recognition.

Effects of Target and Masker Fundamental Frequency Contour Depth on School-Age Children's Speech Recognition in a Two-Talker Masker.

Maturation of the ability to recognize target speech in the presence of a two-talker speech masker extends into early adolescence. This study evaluated whether children benefit from differences in fundamental frequency (f o) contour depth between the target and masker speech, a cue that has been shown to improve recognition in adults. Speech stimuli were recorded from talkers using three speaking styles, with f o contour depths that were Flat, Normal, or Exaggerated. Targets were open-set, declarative sentences produced by a female talker, and maskers were two streams of concatenated sentences produced by a second female talker. Listeners were children (ages 5-17 years) and adults (ages 18-24 years) with normal hearing. Each listener was tested in one of the three masker styles paired with all three target styles. Speech recognition thresholds (SRTs) corresponding to 50% correct were estimated by fitting psychometric functions to adaptive track data. For adults, performance did not differ significantly across conditions with matched speaking styles. A mismatch benefit was observed when combining Flat targets with the Exaggerated masker and Exaggerated targets with the Flat masker, and for both Flat and Exaggerated targets paired with the Normal masker. For children, there was a significant effect of age in all conditions. Flat targets in the Flat masker were associated with lower SRTs than the other two matched conditions, and a mismatch benefit was observed for young children only when the target f o contour was less variable than the masker f o contour. Whereas child-directed speech often has exaggerated pitch contours, young children were better able to recognize speech with less variable f o. Age effects were observed in the benefit of mismatched speaking styles for some conditions, which could be related to differences in baseline SRTs rather than differences in segregation abilities.

Predicting speech-in-speech recognition: Short-term audibility, talker sex, and listener factors.

Speech-in-speech recognition can be challenging, and listeners vary considerably in their ability to accomplish this complex auditory-cognitive task. Variability in performance can be related to intrinsic listener factors as well as stimulus factors associated with energetic and informational masking. The current experiments characterized the effects of short-term audibility of the target, differences in target and masker talker sex, and intrinsic listener variables on sentence recognition in two-talker speech and speech-shaped noise. Participants were young adults with normal hearing. Each condition included the adaptive measurement of speech reception thresholds, followed by testing at a fixed signal-to-noise ratio (SNR). Short-term audibility for each keyword was quantified using a computational glimpsing model for target+masker mixtures. Scores on a psychophysical task of auditory stream segregation predicted speech recognition, with stronger effects for speech-in-speech than speech-in-noise. Both speech-in-speech and speech-in-noise recognition depended on the proportion of audible glimpses available in the target+masker mixture, even across stimuli presented at the same global SNR. Short-term audibility requirements varied systematically across stimuli, providing an estimate of the greater informational masking for speech-in-speech than speech-in-noise recognition and quantifying informational masking for matched and mismatched talker sex.

Evaluating how language and masked-speech recognition change over time for bilingual children in the Midwest

Spanish-English bilingual children living in the US often become more proficient in English compared to Spanish over time, in part due to education models. For example, most bilingual children in the Midwest receive educational instruction in English or rapidly transition to English-only instruction. If a bilingual child’s relative proficiency shifts, how does that shift affect their speech recognition? To address this question, we invited participants from the Children’s English and Spanish Speech Recognition Test (ChEgSS) normative study back three years later to retest their speech recognition. The initial study evaluated word recognition in 83 Spanish-English bilingual children with normal hearing. Children completed Spanish and English word recognition tests in speech-shaped noise and two-talker speech using a 4AFC procedure. Language proficiency and language use were assessed using standardized tests and a questionnaire. Results indicated that age and receptive vocabulary influenced word recognition performance. In this study we retested a subgroup of children who were between the ages of 4-8 years in the initial study using the same procedures. Results will advance our understanding of the association between language proficiency and word recognition in this demographic of bilingual children.

Subjective tinnitus patients with normal pure-tone hearing still suffer more informational masking in the noisy environment.

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.

Masked speech recognition in school-age children with Down syndrome

Masked speech recognition is poorer for children who are typically developing compared to adults, particularly when the masker is two-talker speech. Audibility, receptive vocabulary size, and executive function contribute to these age effects, all areas of weakness for children with Down syndrome. This study sought to determine whether these weaknesses put children with Down syndrome (n = 15, 5–17 yrs) at a disadvantage when listening to masked speech compared to age-matched children who are typically developing. Speech-in-noise and speech-in-speech was assessed using an adaptive, forced-choice procedure with a picture-pointing response. Audiological testing and standardized assessments of receptive vocabulary, non-verbal cognition, and executive function were also completed. Overall, children with Down syndrome performed more poorly than their typically developing peers. While the relationship between age and SRTs differs between the noise and speech maskers for children who are typically developing, this interaction was not observed for children with Down syndrome. Controlling for age, SRTs for children with Down syndrome were associated with vocabulary and executive function scores with the noise masker but not the speech masker. Results suggest that masked speech recognition is more challenging and is limited by different factors for children with Down syndrome compared to those who are typically developing.

Evaluating contributions of relative vocabulary size and demand for use on masked-speech recognition for bilingual children with normal hearing

The Children’s English and Spanish Speech Recognition Test (ChEgSS) is a tool for assessing masked-speech recognition. An audiologist could test a bilingual child’s speech recognition in both English and Spanish, but if time is limited, which language should they choose? We evaluated how two different measures of language dominance, relative demand for use and relative vocabulary size impacted word identification in noise and in a two-talker speech masker for 82 bilingual children (4–17 years) with normal hearing. The participants were exposed to Spanish from birth and varied in their initial exposure to English. Each child completed ChEgSS in English and Spanish using a 4AFC procedure. We measured vocabulary using standardized tests and demand for use using questionnaires. We created language dominance variables by standardizing values then subtracting Spanish scores from English ones. Linear regression evaluated how age and the interaction between length of exposure, relative vocabulary size, and relative language use predicted performance. Relative vocabulary size impacted thresholds, and this effect was larger for children with less exposure in the test language. Results suggest relative vocabulary size and length of exposure should inform the test language(s) used to assess clinical speech recognition.

Effects of F0 contour depth differences on school-age children’s speech recognition in a two-talker masker

This study investigated the extent to which children (ages 5–17) can take advantage of differences in fundamental frequency (F0) contour between target and masker speech to improve speech-in-speech recognition. A number of studies show that differences in F0 and F0 contour between talkers support better speech-in-speech recognition for adults, suggesting it is an important cue for recognizing speech in multitalker environments. However, children’s use of F0 contour differences during speech-in-speech recognition is less well understood. In the present study, sentence recognition was measured adaptively in a two-talker speech masker. Target and masker sentences were recorded with either normal, flat, or exaggerated F0 contours. Results revealed that children’s sentence recognition was impacted by differences in F0 contour depth in both target and masker speech, but the pattern of results differed between children and adults in some conditions. For children, the consistent nature of the flat F0 contour often had a greater impact on speech recognition thresholds (SRTs) than target/masker differences in F0 contour depth. Observed age effects did not appear to be due to limitations in children’s ability to use F0 contour differences in general but are likely related to the perceptual salience of the target contour relative to the masker.

Spatial Hearing and Functional Auditory Skills in Children With Unilateral Hearing Loss.

Purpose The purpose of this study was to characterize spatial hearing abilities of children with longstanding unilateral hearing loss (UHL). UHL was expected to negatively impact children's sound source localization and masked speech recognition, particularly when the target and masker were separated in space. Spatial release from masking (SRM) in the presence of a two-talker speech masker was expected to predict functional auditory performance as assessed by parent report. Method Participants were 5- to 14-year-olds with sensorineural or mixed UHL, age-matched children with normal hearing (NH), and adults with NH. Sound source localization was assessed on the horizontal plane (-90° to 90°), with noise that was either all-pass, low-pass, high-pass, or an unpredictable mixture. Speech recognition thresholds were measured in the sound field for sentences presented in two-talker speech or speech-shaped noise. Target speech was always presented from 0°; the masker was either colocated with the target or spatially separated at ±90°. Parents of children with UHL rated their children's functional auditory performance in everyday environments via questionnaire. Results Sound source localization was poorer for children with UHL than those with NH. Children with UHL also derived less SRM than those with NH, with increased masking for some conditions. Effects of UHL were larger in the two-talker than the noise masker, and SRM in two-talker speech increased with age for both groups of children. Children with UHL whose parents reported greater functional difficulties achieved less SRM when either masker was on the side of the better-hearing ear. Conclusions Children with UHL are clearly at a disadvantage compared with children with NH for both sound source localization and masked speech recognition with spatial separation. Parents' report of their children's real-world communication abilities suggests that spatial hearing plays an important role in outcomes for children with UHL.

The Children’s English and Spanish Speech Recognition Test (ChEgSS): Normative data

The Children’s English and Spanish Speech Recognition Test (ChEgSS) is a clinical tool for assessing children’s English and Spanish word recognition in a noise or two-talker masker. The English and Spanish versions of the test are acoustically, phonetically, and linguistically similar. The goal of this study was to establish threshold norms for Spanish-English bilingual and English monolingual children, and to evaluate effects of age and language proficiency on performance. Participants were 81 Spanish-English bilingual and 89 English monolingual children (4–17 years) with normal hearing. Children completed word recognition testing using an adaptive, 4AFC procedure with a picture-pointing response. All children completed testing in both a noise and a two-talker masker. Bilingual children were tested in English and in Spanish, and monolingual children were tested in English. Language proficiency was assessed using standardized assessments of receptive vocabulary as well as parent report. Both groups of children performed more poorly in two-talker speech than in speech-shaped noise. Preliminary results indicate that age and receptive vocabulary were significant predictors of word recognition performance in both languages and for both maskers. Performance for balanced bilinguals (i.e., similar language proficiency in Spanish and English) was similar for Spanish and English stimuli.

Predicting children's audiovisual speech recognition thresholds based on unimodal performance

This study examined the extent to which individual differences in children’s audiovisual speech recognition thresholds are explained by their performance in unimodal auditory and unimodal visual conditions. Auditory-only and audiovisual speech recognition thresholds were measured in fifty children between 7 and 9 years of age using an adaptive closed-set speech recognition task in a two-talker speech masker. Children heard color-number combinations and responded by choosing the color-number combination on a touch-screen monitor. Visual-only speech recognition accuracy scores were measured using the same stimuli and closed-set response format. Correlations and linear modeling were used to examine the extent to which visual-only speech recognition accuracy, auditory-only speech recognition thresholds, and age predict audiovisual speech recognition thresholds. Audiovisual speech recognition thresholds were positively correlated with auditory-only speech recognition thresholds and negatively correlated with visual-only accuracy. A linear model explained 38% of variance in audiovisual thresholds and indicated that children with better visual-only accuracy had lower audiovisual thresholds. Effects of auditory-only accuracy and age were non-significant. These results suggest that lipreading ability contributes to individual differences in 7- to 9-year-old children’s audiovisual recognition of color-number stimuli in a two-talker speech masker.

How do children combine visual speech with other auditory grouping cues?

Adults use visual speech to help perceptually group talkers into separate objects and to attend to the target talker. As a result, they benefit more from visual speech in the presence of a two-talker speech masker than in speech-spectrum noise and benefit less from visual speech when other cues are available to support auditory grouping. Recent studies demonstrated that children’s visual speech benefit was similar for a noise masker and a two-talker speech masker, suggesting that children may not use visual speech as a grouping cue. The current study further examined whether children use visual speech as a grouping cue by testing whether 40 seven- to nine-year-old children’s visual speech benefit decreased in the presence of other cues known to promote auditory grouping in children, namely carrier phrases and perceived spatial separation. Children completed an adaptive closed-set speech recognition task in a two-talker speech masker, in auditory-only and audiovisual conditions, and in the presence or absence of one of the auditory grouping cues. Preliminary analyses suggest that children’s visual speech benefit did not decrease when other auditory grouping cues were present. These results provide converging evidence that children in this age range may not use visual speech as a grouping cue.

The effects of face masks on speech-in-speech recognition for children and adults

While face masks have been used in medical settings for decades, they have only recently become a part of everyday life due to the COVID-19 pandemic. The implications for how face masks impact speech communication in noise are not well understood, particularly in the pediatric population. Given that previous research has shown that speech recognition in noise is more challenging for children than for adults, it is critical that we examine the effects of face masks on children’s speech understanding in these contexts. The present study explored the effects of different face masks on school-age children’s speech-in-speech recognition. Word recognition was measured in a competing two-talker speech masker. Target words were recorded using a real talker in 5 mask conditions: no mask, surgical, N95, clear plastic, and face shield. Preliminary results indicate that performance was the most negatively impacted when the talker wore a face shield or clear plastic mask. There were no differences between the no-mask condition and either surgical or N95 mask. Acoustic analyses on the target speech were performed to explore causes of these effects. Findings suggest that optimal communication with children may be achieved using surgical or N95 masks as opposed to other mask types.