An Exploration of Voice Quality in Mothers Speaking Canadian English to Infants

Research on the acoustic characteristics of Infant Directed Speech (IDS) in North American English indicates that it is generally higher-pitched than Adult Directed Speech (ADS) and has unique prosodic characteristics, which is commonly found across many spoken languages. However, very little research has addressed another important aspect of prosody: voice quality. In the current study, 25 English-speaking mothers from Canada were recorded speaking to their infant children and to an adult peer. Five acoustic measures of voice quality, including glottal constriction, spectral tilt, Harmonic-to-Noise Ratio (HNR), and Cepstral Peak Prominence (CPP), were analyzed. Only CPP, a measure of the breathiness of a speaker's voice, and corrected H1-A2, a measure of vocal creakiness, were found to be significantly different between the IDS and ADS registers. Sociolinguistic research identifies voice quality as a key indicator of speech style and persona; we connect the pattern of breathiness in IDS to a possible "parental persona" that builds on the affective intent of IDS (rather than the pedagogical intent), with suggestions for future research.