Talker Differences Research Articles

Fundamental frequency predominantly drives talker differences in auditory brainstem responses to continuous speech.

Deriving human neural responses to natural speech is now possible, but the responses to male- and female-uttered speech have been shown to differ. These talker differences may complicate interpretations or restrict experimental designs geared toward more realistic communication scenarios. This study found that when a male talker and a female talker had the same fundamental frequency, auditory brainstem responses (ABRs) were very similar. Those responses became smaller and later with increasing fundamental frequency, as did click ABRs with increasing stimulus rates. Modeled responses suggested that the speech and click ABR differences were reasonably predicted by peripheral and brainstem processing of stimulus acoustics.

Fundamental frequency predominantly drives talker differences in auditory brainstem responses to continuous speech.

Deriving human neural responses to natural speech is now possible, but the responses to male- and female-uttered speech have been shown to differ. These talker differences may complicate interpretations or restrict experimental designs geared toward more realistic communication scenarios. This study found that when a male and female talker had the same fundamental frequency, auditory brainstem responses (ABRs) were very similar. Those responses became smaller and later with increasing fundamental frequency, as did click ABRs with increasing stimulus rates. Modeled responses suggested that the speech and click ABR differences were reasonably predicted by peripheral and brainstem processing of stimulus acoustics.

Perception and recognition of English /s/ and /ʃ/ with varying acoustic-auditory contrast

Seminal work (Newman et al., JASA, 2001) found that listeners’ responses to talkers with more variable fricative productions were slower, though listeners’ ability to categorize the varied fricatives was robust. The current study selects North American English-speaking talkers with /s/ and / ʃ/ productions that varying in the magnitude of the acoustic-auditory contrast. With selected speech samples, listeners were asked to categorize (1) the isolated fricative (C- only), (2) the fricative-vowel sequence (CV), or (3) to complete a speeded-shadowing task where listeners were auditorily presented with the full words and asked to identify the words by repeating them as quickly and accurately as possible. Data were analyzed with Bayesian methods. The fricatives from talkers with greater contrast were identified more accurately and more quickly, with a greater effect size for the C-only condition and /s/ productions. This suggests listeners leverage information from the formant transitions to differentiate these fricatives. The speeded-shadowing results indicate the participants are faster at identifying the words with less acoustic-auditory contrast. This is the opposite of the expected pattern. Coupling C-only, CV, and word-level responses paints a more accurate picture of how talker differences in auditory- acoustic contrast affect categorization and intelligibility.

Racialization and sentence intelligibility in older adults with hearing impairment

Previous studies have shown that the perception of a talker’s racial identity affects the intelligibility of that person’s speech to younger, normal-hearing listeners (Babel & Russell, 2015; McGowan, 2015; Tripp, Lyons, & Munson, 2022). These findings show that social perception influences intelligibility. These effects are thought to reflect varied experiences interacting with racially diverse individuals, attitudes and beliefs about different racial groups, or a combination of these factors. The current experiment examines whether the strength of the influence of perceived racial identity on intelligibility is similar across different age groups and levels of hearing acuity. Participants (n = 42, including 16 normal hearing [NH] younger adults, 11 NH older adults, and 15 older adults with hearing loss) were played sentences produced by four talkers who varied in racial identity, in audio-only and audiovisual conditions, in background noise and reported what they heard. Participants also completed a measure of attitudes toward the four talkers. Analyses are ongoing, and examine (1) whether the influence of presentation modality on intelligibility varies across the four talkers, (2) whether these talker differences in audiovisual benefit vary across the three listener groups, and (3) whether attitudes toward the talkers predict intelligibility. [Funding: NIH grant R21 DC018070]

Development of a Sentence Verification Task to Measure Speech Comprehension and Listening Effort in Cochlear Implant Users.

Tests measuring speech comprehension and listening effort for cochlear implant (CI) users may reflect important aspects of real-world speech communication. In this study, we describe the development of a multiple-talker, English-language sentence verification task (SVT) for use in adult CI users to measure speech comprehension and listening effort. We also examine whether talker differences affect speech comprehension and listening effort. Thirteen experienced adult CI users participated in the study and underwent testing using a newly developed multiple-talker SVT. Participants were sequentially presented with audio recordings of unique sentences spoken in English by six different talkers. Participants classified each sentence as either true or false. Accuracy of classification and the response time (RT) for correct responses were used as measures of comprehension and listening effort, respectively. The effect of talker on the results was further analyzed. All 13 participants successfully completed the SVT. The mean verification accuracy for participants was 87.2% ± 8.8%. The mean RT for correct responses across participants was 1,050 ms ± 391 ms. When stratified by talker, verification accuracy ranged from 83.7% to 95.2% and mean RTs across participant ranged from 786 ms to 1,254 ms. Talker did not have a significant effect on sentence classification accuracy, but it did have a significant effect on RTs (p < .001). The SVT is an easily implemented test that can assess speech comprehension and listening effort simultaneously. CI users may experience increased effort for comprehending certain talkers' speech, despite showing similar levels of comprehension accuracy. https://doi.org/10.23641/asha.24126630.

Normalization of speech kinematic data for characterizing primary muscle tension dysphonia

Primary muscle tension dysphonia (pMTD) is a voice disorder of unknown etiology in which people have reduced volume and become easily fatigued. The tongue has biomechanical linkage to the laryngeal motor system that affects the voice, suggesting that tongue movement variability might be a marker for this disorder. Previous studies of healthy/disordered speech have reduced individual talker differences in physical vocal tract characteristics via normalization procedures. Here, we obtained tongue movement data for diadochokinetic sequences produced by healthy adult talkers and people with pMTD. We used an electromagnetic articulography system to test three healthy adult talkers and a participant with pMTD. We recorded vertical displacement of the tongue dorsum for sustained /a/ and 30 sec of rapidly repeated /pataka/. Displacement (mm) was scaled relative to each talker’s sustained vowel production, while movement time (msec) was normalized by dividing each /ka/ portion by the corresponding /pataka/ utterance length. The results suggest (1) normalization effectively reduced talker variability in tongue movement displacement and timing, and (2) the talker with pMTD showed markedly higher temporal variability, compared to the control talkers. We are currently testing this putative group difference using additional participants.

Tracking talker-specific cues to lexical stress: Evidence from perceptual learning.

When recognizing spoken words, listeners are confronted by variability in the speech signal caused by talker differences. Previous research has focused on segmental talker variability; less is known about how suprasegmental variability is handled. Here we investigated the use of perceptual learning to deal with between-talker differences in lexical stress. Two groups of participants heard Dutch minimal stress pairs (e.g., VOORnaam vs. voorNAAM, "first name" vs. "respectable") spoken by two male talkers. Group 1 heard Talker 1 use only F0 to signal stress (intensity and duration values were ambiguous), while Talker 2 used only intensity (F0 and duration were ambiguous). Group 2 heard the reverse talker-cue mappings. After training, participants were tested on words from both talkers containing conflicting stress cues ("mixed items"; e.g., one spoken by Talker 1 with F0 signaling initial stress and intensity signaling final stress). We found that listeners used previously learned information about which talker used which cue to interpret the mixed items. For example, the mixed item described above tended to be interpreted as having initial stress by Group 1 but as having final stress by Group 2. This demonstrates that listeners learn how individual talkers signal stress and use that knowledge in spoken-word recognition. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Revisiting the left ear advantage for phonetic cues to talker identification.

Previous research suggests that learning to use a phonetic property [e.g., voice-onset-time, (VOT)] for talker identity supports a left ear processing advantage. Specifically, listeners trained to identify two "talkers" who only differed in characteristic VOTs showed faster talker identification for stimuli presented to the left ear compared to that presented to the right ear, which is interpreted as evidence of hemispheric lateralization consistent with task demands. Experiment 1 (n = 97) aimed to replicate this finding and identify predictors of performance; experiment 2 (n = 79) aimed to replicate this finding under conditions that better facilitate observation of laterality effects. Listeners completed a talker identification task during pretest, training, and posttest phases. Inhibition, category identification, and auditory acuity were also assessed in experiment 1. Listeners learned to use VOT for talker identity, which was positively associated with auditory acuity. Talker identification was not influenced by ear of presentation, and Bayes factors indicated strong support for the null. These results suggest that talker-specific phonetic variation is not sufficient to induce a left ear advantage for talker identification; together with the extant literature, this instead suggests that hemispheric lateralization for talker-specific phonetic variation requires phonetic variation to be conditioned on talker differences in source characteristics.

Individual Differences in Phonetic Plasticity Across Native and Nonnative Contexts.

Purpose Individuals vary in their ability to learn the sound categories of nonnative languages (nonnative phonetic learning) and to adapt to systematic differences, such as accent or talker differences, in the sounds of their native language (native phonetic learning). Difficulties with both native and nonnative learning are well attested in people with speech and language disorders relative to healthy controls, but substantial variability in these skills is also present in the typical population. This study examines whether this individual variability can be organized around a common ability that we label "phonetic plasticity." Method A group of healthy young adult participants (N = 80), who attested they had no history of speech, language, neurological, or hearing deficits, completed two tasks of nonnative phonetic category learning, two tasks of learning to cope with variation in their native language, and seven tasks of other cognitive functions, distributed across two sessions. Performance on these 11 tasks was compared, and exploratory factor analysis was used to assess the extent to which performance on each task was related to the others. Results Performance on both tasks of native learning and an explicit task of nonnative learning patterned together, suggesting that native and nonnative phonetic learning tasks rely on a shared underlying capacity, which is termed "phonetic plasticity." Phonetic plasticity was also associated with vocabulary, comprehension of words in background noise, and, more weakly, working memory. Conclusions Nonnative sound learning and native language speech perception may rely on shared phonetic plasticity. The results suggest that good learners of native language phonetic variation are also good learners of nonnative phonetic contrasts. Supplemental Material https://doi.org/10.23641/asha.16606778.

Talker familiarity and the accommodation of talker variability.

A fundamental problem in speech perception is how (or whether) listeners accommodate variability in the way talkers produce speech. One view of the way listeners cope with this variability is that talker differences are normalized - a mapping between talker-specific characteristics and phonetic categories is computed such that speech is recognized in the context of the talker's vocal characteristics. Consistent with this view, listeners process speech more slowly when the talker changes randomly than when the talker remains constant. An alternative view is that speech perception is based on talker-specific auditory exemplars in memory clustered around linguistic categories that allow talker-independent perception. Consistent with this view, listeners become more efficient at talker-specific phonetic processing after voice identification training. We asked whether phonetic efficiency would increase with talker familiarity by testing listeners with extremely familiar talkers (family members), newly familiar talkers (based on laboratory training), and unfamiliar talkers. We also asked whether familiarity would reduce the need for normalization. As predicted, phonetic efficiency (word recognition in noise) increased with familiarity (unfamiliar < trained-on < family). However, we observed a constant processing cost for talker changes even for pairs of family members. We discuss how normalization and exemplar theories might account for these results, and constraints the results impose on theoretical accounts of phonetic constancy.

Talker differences in clear and conversational speech: Perceived emotional valence

Clear speech, a speaking style talkers adopt when talking to individuals with hearing loss, is often described as sounding “angry” (e.g., “I try to speak clearly, but when I do, he thinks I'm mad at him”). Previous research has indicated that listeners do indeed rate clear speech as “angry” or “disgusted” more often than conversational speech. However, this same research found that some talkers can increase the clarity of their speech without sounding angry. The present study expands the previous work by testing perceived emotion for 41 talkers in order to examine talker differences in the perceived emotional valence of clear and conversational speech. Perceptual ratings from 25 young adults with normal hearing will be gathered using an online experiment interface. Stimuli consist of 14 emotionally neutral sentences in both clear and conversational speaking styles from 41 talkers. Listeners will be asked to “judge the emotion you think you heard in that sentence” using a six-alternative, forced-choice paradigm for thefollowing emotional categories: “anger,” “fear,” “disgust,” “sadness,” “happiness,” and “neutral.” It is anticipated that the current study will increase our understanding of how perceived emotional valence in clear and conversational speaking styles varies among talkers.

Perceptual weighting of acoustic cues for accommodating gender-related talker differences heard by listeners with normal hearing and with cochlear implants.

Listeners must accommodate acoustic differences between vocal tracts and speaking styles of conversation partners-a process called normalization or accommodation. This study explores what acoustic cues are used to make this perceptual adjustment by listeners with normal hearing or with cochlear implants, when the acoustic variability is related to the talker's gender. A continuum between /ʃ/ and /s/ was paired with naturally spoken vocalic contexts that were parametrically manipulated to vary by numerous cues for talker gender including fundamental frequency (F0), vocal tract length (formant spacing), and direct spectral contrast with the fricative. The goal was to examine relative contributions of these cues toward the tendency to have a lower-frequency acoustic boundary for fricatives spoken by men (found in numerous previous studies). Normal hearing listeners relied primarily on formant spacing and much less on F0. The CI listeners were individually variable, with the F0 cue emerging as the strongest cue on average.

The relationship between talker acoustics, intelligibility, and effort in degraded listening conditions.

Listening to degraded speech is associated with decreased intelligibility and increased effort. However, listeners are generally able to adapt to certain types of degradations. While intelligibility of degraded speech is modulated by talker acoustics, it is unclear whether talker acoustics also affect effort and adaptation. Moreover, it has been demonstrated that talker differences are preserved across spectral degradations, but it is not known whether this effect extends to temporal degradations and which acoustic-phonetic characteristics are responsible. In a listening experiment combined with pupillometry, participants were presented with speech in quiet as well as in masking noise, time-compressed, and noise-vocoded speech by 16 Southern British English speakers. Results showed that intelligibility, but not adaptation, was modulated by talker acoustics. Talkers who were more intelligible under noise-vocoding were also more intelligible under masking and time-compression. This effect was linked to acoustic-phonetic profiles with greater vowel space dispersion (VSD) and energy in mid-range frequencies, as well as slower speaking rate. While pupil dilation indicated increasing effort with decreasing intelligibility, this study also linked reduced effort in quiet to talkers with greater VSD. The results emphasize the relevance of talker acoustics for intelligibility and effort in degraded listening conditions.

Cortical mechanisms of talker normalization in fluent sentences

Adjusting to the vocal characteristics of a new talker is important for speech recognition. Previous research has indicated that adjusting to talker differences is an active cognitive process that depends on attention and working memory (WM). These studies have not examined how talker variability affects perception and neural responses in fluent speech. Here we use source analysis from high-density EEG to show that perceiving fluent speech in which the talker changes recruits early involvement of parietal and temporal cortical areas, suggesting functional involvement of WM and attention in talker normalization. We extend these findings to acoustic source change in general by examining understanding environmental sounds in spoken sentence context. Though there may be differences in cortical recruitment to processing demands for non-speech sounds versus a changing talker, the underlying mechanisms are similar, supporting the view that shared cognitive-general mechanisms assist both talker normalization and speech-to-nonspeech transitions.

Individual Talker Differences in VOT: Salience Filtering Mechanism

Individual Talker Differences in VOT: Salience Filtering Mechanism

Effects of talker variability on spoken word recognition for adult cochlear implant users

Cochlear implants (CIs) have been highly successful in providing a restored sense of hearing to profoundly deaf individuals. However, CI users must rely on a signal that is highly degraded in acoustic-phonetic details, conveying limited talker information. Normal-hearing (NH) listeners devote processing resources to accommodating talkers’ voices, and show less accurate and slower word recognition in multiple-talker compared to single-talker conditions. CI users may display a different strategy in adapting to new talkers due to limitations in talker discrimination. The current study examined the effects of talker variability on spoken word recognition by experienced, post-lingually deafened adult CI users, and the extent to which talker variability effects are mediated by limitations in talker discrimination. Word recognition accuracy for lexically easy and hard words were obtained in single-talker and multiple-talker conditions, varying by gender (female, male, mixed). Results demonstrated that single-talker performance was highly variable, but a detrimental effect of talker variability was observed in mixed conditions, when talker differences were best discriminated, particularly for hard lexical items. Taken together, findings suggest that while CI users may be affected less by talker variability overall, they may display a similar strategy as NH listeners for talker adaptation when talker differences are discriminable.

The effect of talker variability on word recognition under cochlear implant simulation

Normal-hearing (NH) listeners have been shown to be less accurate and/or slower to recognize spoken words when the talker changes from trial to trial, compared to when the talker remains the same. Less is known about the effect of talker variability on cochlear implant (CI) users, who display a limitation in talker perception. As a first step, the current study investigated how limited talker information via CI simulation influences word recognition. In two experiments, NH listeners completed a word naming task in different talker conditions (single (ST), multiple female (MT-F), and multiple female/male (MT-M)) and simulation conditions (12, 8, and 4 vocoder channels). An effect of talker variability was observed, but only when talker differences were maximized. Listeners were less accurate, but not slower, at recognizing words under the MT-M condition, compared to ST and MT-F conditions. Talker variability effects did not vary by the simulation condition. These results are consistent with previous studies with NH listeners, showing similar performance in conditions where talker changes were not detected but talker differences were large. Taken together, these findings suggest that limitations in talker perception for NH listeners under CI simulation, and potentially CI users, alters the perceptual strategy for recognizing words under multiple-talker conditions.Normal-hearing (NH) listeners have been shown to be less accurate and/or slower to recognize spoken words when the talker changes from trial to trial, compared to when the talker remains the same. Less is known about the effect of talker variability on cochlear implant (CI) users, who display a limitation in talker perception. As a first step, the current study investigated how limited talker information via CI simulation influences word recognition. In two experiments, NH listeners completed a word naming task in different talker conditions (single (ST), multiple female (MT-F), and multiple female/male (MT-M)) and simulation conditions (12, 8, and 4 vocoder channels). An effect of talker variability was observed, but only when talker differences were maximized. Listeners were less accurate, but not slower, at recognizing words under the MT-M condition, compared to ST and MT-F conditions. Talker variability effects did not vary by the simulation condition. These results are consistent with previous studie...

Backwards and indirect context effects in accommodating gender differences in speech

Listeners accommodate large amount of acoustic variability across talkers and phonetic contexts when categorizing speech sounds. This study examines accommodation of gender-related talker differences, which can occur in reverse (in sound sequence AB, sound B affects perception of sound A), suggesting more complicated mechanisms than peripheral auditory contrast enhancement alone. A continuum of fricatives “sh” and “s” was preappended to vowels whose acoustic parameters were manipulated by various properties ranging from typically feminine to masculine and vice versa. Other conditions provided matching or mis-matching visual cues. We examined the weighting of cues to talker gender, the duration of exposure to sound needed to obtain the full context effect, and the influence of hearing status, using listeners with cochlear implants (CIs). CI listeners used different cues to show a comparable gender context effect and also appear to use proxy cues for acoustic properties perceived more clearly by people with normal hearing (NH). All listeners showed implicit knowledge of how acoustic patterns are selectively reverse-compatible with different articulation sequences. NH listeners needed only 30 ms for full adjustment, while CI listeners’ data were much more variable. Collectively, these results show a complex process of auditory, visual and gesture-aware adjustment to a talker’s voice.Listeners accommodate large amount of acoustic variability across talkers and phonetic contexts when categorizing speech sounds. This study examines accommodation of gender-related talker differences, which can occur in reverse (in sound sequence AB, sound B affects perception of sound A), suggesting more complicated mechanisms than peripheral auditory contrast enhancement alone. A continuum of fricatives “sh” and “s” was preappended to vowels whose acoustic parameters were manipulated by various properties ranging from typically feminine to masculine and vice versa. Other conditions provided matching or mis-matching visual cues. We examined the weighting of cues to talker gender, the duration of exposure to sound needed to obtain the full context effect, and the influence of hearing status, using listeners with cochlear implants (CIs). CI listeners used different cues to show a comparable gender context effect and also appear to use proxy cues for acoustic properties perceived more clearly by people with...

Distributional learning for speech reflects cumulative exposure to a talker's phonetic distributions.

Efficient speech perception requires listeners to maintain an exquisite tension between stability of the language architecture and flexibility to accommodate variation in the input, such as that associated with individual talker differences in speech production. Achieving this tension can be guided by top-down learning mechanisms, wherein lexical information constrains interpretation of speech input, and by bottom-up learning mechanisms, in which distributional information in the speech signal is used to optimize the mapping to speech sound categories. An open question for theories of perceptual learning concerns the nature of the representations that are built for individual talkers: do these representations reflect long-term, global exposure to a talker or rather only short-term, local exposure? Recent research suggests that when lexical knowledge is used to resolve a talker's ambiguous productions, listeners disregard previous experience with a talker and instead rely on only recent experience, a finding that is contrary to predictions of Bayesian belief-updating accounts of perceptual adaptation. Here we use a distributional learning paradigm in which lexical information is not explicitly required to resolve ambiguous input to provide an additional test of global versus local exposure accounts. Listeners completed two blocks of phonetic categorization for stimuli that differed in voice-onset-time, a probabilistic cue to the voicing contrast in English stop consonants. In each block, two distributions were presented, one specifying /g/ and one specifying /k/. Across the two blocks, variance of the distributions was manipulated to be either narrow or wide. The critical manipulation was order of the two blocks; half of the listeners were first exposed to the narrow distributions followed by the wide distributions, with the order reversed for the other half of the listeners. The results showed that for earlier trials, the identification slope was steeper for the narrow-wide group compared to the wide-narrow group, but this difference was attenuated for later trials. The between-group convergence was driven by an asymmetry in learning between the two orders such that only those in the narrow-wide group showed slope movement during exposure, a pattern that was mirrored by computational simulations in which the distributional statistics of the present talker were integrated with prior experience with English. This pattern of results suggests that listeners did not disregard all prior experience with the talker, and instead used cumulative exposure to guide phonetic decisions, which raises the possibility that accommodating a talker's phonetic signature entails maintaining representations that reflect global experience.

Re-examining the effect of top down processing on voice perception

The current study aimed to replicate a recent study conducted by Narayan, Mak, &amp; Bialystok (2016) that found effects of top-down linguistic information on a talker discrimination task by comparing four conditions: compounds (day-dream), rhymes (day-bay), reverse compounds (dream-day), and unrelated words (day-bee). The original study used both within- and across-gender pairs and same and different trials were analyzed separately, obscuring possible response biases. Narayan et al. found graded performance between the four conditions, but some results were likely to have been influenced by the use of across-gender trials in the different-talker condition. In the current study, only female speakers were used and results were analyzed with signal detection theory (sensitivity and bias measures). Results revealed that participants were faster to respond to rhyming pairs than the three other conditions. In addition, participants were significantly more sensitive to talker differences in rhyming pairs than unrelated pairs, but no other conditions differed. Participants were more biased to respond “same” in the rhyme and compound conditions than in the unrelated condition. These results demonstrate a partial replication of the Narayan, Mak, &amp; Bialystok (2016) findings, suggesting an interaction between linguistic and talker information during speech perception.