College of Behavioral & Social Sciences
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Item Adult discrimination of children’s voices over time: Voice discrimination of auditory samples from longitudinal research studies(2024) Opusunju, Shelby; Bernstein Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The human voice is subject to change over the lifespan, and these changes are even more pronounced in children. Acoustic properties of speech, such as fundamental frequency, amplitude, speech rate, and fluency, change dramatically as children grow and develop (Lee et al., 1999). Previous studies have established that listeners have a generally strong capacity to discriminate between adult speakers, as well as identify the age of a speaker, based solely on the voice (Kreiman and Sidtis, 2011; Park, 2019). However, few studies have been performed on the listener’s capacity to discriminate between the voices of children, particularly as the voice matures over time. This study examines how well adult listeners can discriminate between the voices of young children of the same age and at different ages. Single-word child language samples from different children (N = 6) were obtained from Munson et al. (2021) and used to create closed-set online AX voice discrimination tasks for adult listeners (N= 31). Three tasks examined listeners’ accuracy and sensitivity in identifying whether a voice was that of the same child or a different child under three conditions: 1) between two children that are both three-years old, 2) between two children that are five-years old, and 3) between two children of different ages (three- vs. five-years old). Listeners’ performance showed above-chance levels of accuracy and sensitivity at discriminating between the voices of children at three-years-old and at two children at five-years-old. Listener performance was not significantly different in these two tasks. No listeners demonstrated above-chance levels of accuracy in discriminating between the voices of a single child at two different ages. Listener performance was significantly poorer in this task compared to the previous two. The findings from this experiment demonstrated a sizable difference in adults' ability to recognize child voices at two different ages than at one age. Possible explanations and implications for understanding child talker discrimination across different ages are discussed.Item Evaluating the role of acoustic cues in identifying the presence of a code-switch(2024) Exton, Erika Lynn; Newman, Rochelle S.; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Code-switching (switching between languages) is a common linguistic behavior in bilingual speech directed to infants and children. In adult-directed speech (ADS), acoustic-phonetic properties of one language may transfer to the other language close to a code-switch point; for example, English stop consonants may be more Spanish-like near a switch. This acoustically-natural code-switching may be easier for bilingual listeners to comprehend than code-switching without these acoustic changes; however, it effectively results in the languages being more phonetically similar at the point of a code-switch, which could make them difficult for an unfamiliar listener to distinguish. The goal of this research was to assess the acoustic-phonetic cues to code-switching available to listeners unfamiliar with the languages by studying the perception and production of these cues. In Experiment 1 Spanish-English bilingual adults (particularly those who hear code-switching frequently), but not English monolingual adults, were sensitive to natural acoustic cues to code-switching in unfamiliar languages and could use them to identify language switches between French and Mandarin. Such cues were particularly helpful when they allowed listeners to anticipate an upcoming language switch (Experiment 2). In Experiment 3 monolingual children appeared unable to continually identify which language they were hearing. Experiment 4 provides some preliminary evidence that monolingual infants can identify a switch between French and Mandarin, though without addressing the utility of natural acoustic cues for infants. The acoustic detail of code-switched speech to infants was investigated to evaluate how acoustic properties of bilingual infant-directed speech (IDS) are impacted by the presence of and proximity to code-switching. Spanish-English bilingual women narrated wordless picture books in IDS and ADS, and the voice onset times of their English voiceless stops were analyzed in code-switching and English-only stories in each register. In ADS only, English voiceless stops that preceded an English-to-Spanish code-switch and were closer to that switch point were produced with more Spanish-like voice onset times than more distant tokens. This effect of distance to Spanish on English VOTs was not true for tokens that followed Spanish in ADS, or in either direction in IDS, suggesting that parents may avoid producing these acoustic cues when speaking to young children.Item Read my lips! Perception of speech in noise by preschool children with autism and the impact of watching the speaker’s face(Springer Nature, 2021-01-05) Newman, Rochelle S.; Kirby, Laura A.; Von Holzen, Katie; Redcay, ElizabethAdults and adolescents with autism spectrum disorders show greater difficulties comprehending speech in the presence of noise. Moreover, while neurotypical adults use visual cues on the mouth to help them understand speech in background noise, differences in attention to human faces in autism may affect use of these visual cues. No work has yet examined these skills in toddlers with ASD, despite the fact that they are frequently faced with noisy, multitalker environments.Item The Role of Age and Bilingualism on Perception of Vocoded Speech(2020) Waked, Arifi Noman; Goupell, Matthew J; Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines the role of age and bilingualism on perception of vocoded speech in order to determine whether bilingual individuals, children, and bilingual individuals with later ages of second language acquisition show greater difficulties in vocoded speech perception. Measures of language skill and verbal inhibition were also examined in relation to vocoded speech perception. Two studies were conducted, each of which had two participant language groups: Monolingual English speakers and bilingual Spanish-English speakers. The first study also explored the role of age at the time of testing by including both monolingual and bilingual children (8-10 years), and monolingual and bilingual adults (18+ years). As such, this study included four total groups of adult and child language pairs. Participants were tested on vocoded stimuli simulating speech as perceived through an 8-channel CI in conditions of both deep (0-mm shift) and shallow (6-mm shift) insertion of the electrode array. Between testing trials, participants were trained on the more difficult, 6-mm shift condition. The second study explored the role of age of second language acquisition in native speakers of Spanish (18+ years) first exposed to English at ages ranging from 0 to 12 years. This study also included a control group of monolingual English speakers (18+ years). This study examined perception of target lexical items presented either in isolation or at the end of sentences. Stimuli in this study were either unaltered or vocoded to simulate speech as heard through an 8-channel CI at 0-mm shift. Items presented in isolation were divided into differing levels of difficulty based on frequency and neighborhood density. Target items presented at the ends of sentences were divided into differing levels of difficulty based on the degree of semantic context provided by the sentence. No effects of age at testing or age of acquisition were found. In the first study, there was also no effect of language group. All groups improved with training and showed significant improvement between pre- and post-test speech perception scores in both conditions of shift. In the second study, all participants were significantly negatively impacted by vocoding; however, bilingual participants showed greater difficulty in perception of vocoded lexical items presented in isolation relative to their monolingual peers. This group difference was not found in sentence conditions, where all participants significantly benefited from greater semantic context. From this, we can conclude that bilingual individuals can make use of semantic context to perceive vocoded speech similarly to their monolingual peers. Neither language skills nor verbal inhibition, as measured in these studies, were found to significantly impact speech perception scores in any of the tested conditions across groups.Item The use of acoustic cues in phonetic perception: Effects of spectral degradation, limited bandwidth and background noise(2011) Winn, Matthew Brandon; Chatterjee, Monita; Idsardi, William J; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hearing impairment, cochlear implantation, background noise and other auditory degradations result in the loss or distortion of sound information thought to be critical to speech perception. In many cases, listeners can still identify speech sounds despite degradations, but understanding of how this is accomplished is incomplete. Experiments presented here tested the hypothesis that listeners would utilize acoustic-phonetic cues differently if one or more cues were degraded by hearing impairment or simulated hearing impairment. Results supported this hypothesis for various listening conditions that are directly relevant for clinical populations. Analysis included mixed-effects logistic modeling of contributions of individual acoustic cues for various contrasts. Listeners with cochlear implants (CIs) or normal-hearing (NH) listeners in CI simulations showed increased use of acoustic cues in the temporal domain and decreased use of cues in the spectral domain for the tense/lax vowel contrast and the word-final fricative voicing contrast. For the word-initial stop voicing contrast, NH listeners made less use of voice-onset time and greater use of voice pitch in conditions that simulated high-frequency hearing impairment and/or masking noise; influence of these cues was further modulated by consonant place of articulation. A pair of experiments measured phonetic context effects for the "s/sh" contrast, replicating previously observed effects for NH listeners and generalizing them to CI listeners as well, despite known deficiencies in spectral resolution for CI listeners. For NH listeners in CI simulations, these context effects were absent or negligible. Audio-visual delivery of this experiment revealed enhanced influence of visual lip-rounding cues for CI listeners and NH listeners in CI simulations. Additionally, CI listeners demonstrated that visual cues to gender influence phonetic perception in a manner consistent with gender-related voice acoustics. All of these results suggest that listeners are able to accommodate challenging listening situations by capitalizing on the natural (multimodal) covariance in speech signals. Additionally, these results imply that there are potential differences in speech perception by NH listeners and listeners with hearing impairment that would be overlooked by traditional word recognition or consonant confusion matrix analysis.Item Infant Speech-in-Noise Perception and Later Phonological Awareness: A Longitudinal Study(2008-10-20) Stimley, Sarah Elizabeth; Newman, Rochelle; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While differences have been found in the ability of infants on a variety of speech perception skills including speech perception in the presence of background noise, the implications of these differences on later language skills are currently unknown. This study examines the relationship between a specific measure of infant speech perception in noise and later phonological awareness outcomes. In order to test this relationship, individuals who participated in Newman's (2005) study on infant speech perception in the presence of background noise were administered a battery of language, phonological awareness, and intelligence tests. Scores from these tests were analyzed to see if performance differences existed between those who had performed well as infants in the original study and those who had not. No significant differences between these two groups were found on the phonological awareness measures. Potential reasons for these findings and suggestions for future research are discussed.