Some acoustical correlates of speech-rate perception

A previous study by the authors found that vocal frequency and intensity both influenced the perception of speech rate, and proposed three alternative explanations of the results. They argued that the findings were a function of: a methodological limitation; the exception that if one speech characteristic changes, the others change in a similar direction; or experience with producing and hearing covariation among pitch, loudness, and speech rate in ordinary speech. The present study tested the hypothesis that such covariation does occur in the perception of speech, and assessed the plausibility of the three explanations. Three levels of frequency and intensity were factorially varied within each of three different speech rates, using a 20-s speech segment played backwards to produce the stimuli. Each stimulus was compared with a standard stimulus in terms of four scales—perceived speech rate, pitch, loudness, and duration—by 21 males and 40 females. ANOVAs indicated that frequency and intensity positively influenced the perception of speech rate, pitch, and loudness, and that frequency negatively affected the perception of duration. The results suggest the third explanation above as the most viable.