Child-Directed Speech in Noise: Testing Signal- and Code-Based Phonetic Enhancement.

PURPOSE: Talkers adapt their speech according to the demands of their listeners and the communicative context, enhancing the properties of the signal (pitch, intensity) and/or properties of the code (enhancement of phonemic contrasts). This study asked how mothers adapt their child-directed speech (CDS) in ways that might serve the immediate goals of increasing intelligibility, as well as long-term goals of supporting speech and language development in their children. METHOD: Mothers (N = 28) participated in a real-time interactive speech production/perception paradigm, in which mothers instructed their young (3- to 5-year-old) children, or an adult listener, to select the picture corresponding to a target word. The task was performed at low and high levels (56 vs. 75 dB SPL) of background noise to examine the Lombard effects of decreased audibility on speech production. RESULTS: Acoustic-phonetic analyses of CDS and adult-directed speech (ADS) productions of target words and carrier phrase (e.g., "Find pig") revealed that mothers significantly enhanced the mean pitch, pitch variability, and intensity of target words in CDS, particularly at higher background noise levels and for younger children. Mothers produce CDS with a higher signal-to-noise ratio than ADS. However, limited evidence was found for phonetic enhancement of the segmental properties of speech. Although increased category separation was found in the voice onset time of stop consonants, decreased vowel category separation (an anti-enhancement effect) was observed in CDS. CONCLUSIONS: Mothers readily enhance the suprasegmental signal properties of their speech in CDS, but not the acoustic-phonetic properties of phonemes. This study fails to provide evidence of phonetic enhancement in preschool children in a dyadic communication task under noisy listening conditions. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.24645423.

Applying Virtual Reality to Audiovisual Speech Perception Tasks in Children.

Purpose The primary purpose of this study was to explore the efficacy of using virtual reality (VR) technology in hearing research with children by comparing speech perception abilities in a typical laboratory environment and a simulated VR classroom environment. Method The study included 48 final participants (40 children and eight young adults). The study design utilized a speech perception task in conjunction with a localization demand in auditory-only (AO) and auditory-visual (AV) conditions. Tasks were completed in simulated classroom acoustics in both a typical laboratory environment and in a virtual classroom environment accessed using an Oculus Rift head-mounted display. Results Speech perception scores were higher for AV conditions over AO conditions across age groups. In addition, interaction effects of environment (i.e., laboratory environment and VR classroom environment) and visual accessibility (i.e., AV vs. AO) indicated that children's performance on the speech perception task in the VR classroom was more similar to their performance in the laboratory environment for AV tasks than it was for AO tasks. AO tasks showed improvement in speech perception scores from the laboratory to the VR classroom environment, whereas AV conditions showed little significant change. Conclusion These results suggest that VR head-mounted displays are a viable research tool in AV tasks for children, increasing flexibility for audiovisual testing in a typical laboratory environment.