Comparison of acoustic characteristics of American English tense and lax vowels in maternal speech to prelingually deaf infants, normal‐hearing infants, and adults.

Abstract

Recent studies have demonstrated that mothers exaggerate phonetic properties of infant‐directed (ID) speech. However, these studies focused on a single acoustic dimension, i.e., frequency, whereas speech sounds are composed of multiple acoustic cues. Moreover, little is known how mothers adjust phonetic properties of speech to children with hearing loss. This study examined the mothers’ production of frequency and duration cues to the American English tense/lax vowel contrast in speech to profoundly deaf (N = 12) and normal‐hearing (N = 12) infants and to an adult experimenter. First and second formant frequencies and vowel duration of tense ([i, [u]) and lax ([i], [u]) vowels were measured. Results demonstrated that mothers exaggerated vowel duration in ID relative to adult‐directed speech. However, only a trend suggesting an exaggeration of vowel space in ID speech was observed. These findings suggest that although both spectral and duration cues to the tense/lax distinction are modified in a systematic...