The Acoustic Parameters of Stress in Relation to Syllable Position, Speech Loudness and Rate

Previous research suggests that at the acoustic level stress is characterized by a complex trading relationship between syllabic fundamental frequency, duration, and amplitude. The present investigation was an attempt to isolate certain speech variables which in addition to phonetic quality and context may exert consistent influences on this trading relationship. Recordings were made of ten speakers' productions of the sentences " Say /'sasa/ please " and " Say /sa'sa/ please " spoken at normal, increased, and decreased rates and loudness of utterance. Spectrographic and oscilloscopic analysis of /'sasa/ and /sa'sa/ revealed the following: (1) Syllable position is a highly significant determiner of the acoustic character of stress, fundamental frequency contrast predominating in /'sαsα/ and duration contrast predominating in /sα'sα/; (2) Fundamental frequency and amplitude contrast between stressed and unstressed syllabics is significantly less during soft speech as compared to normal speech, suggesting that duration is the predominant feature of stress during soft speech; (3) Increased and decreased rate of utterance were not found to have significant effects on the degree of duration contrast between stressed and unstressed syllabics.