Pitch Variability, Speaking Rate, and Low-Frequency Modulation Affect Perception of Anger in Clear Speech

Clear speech, a speaking style used to communicate with individuals with hearing loss and other communication difficulties, has been shown to sound “angry” more often than conversational speech (Morgan & Ferguson, 2017). In this study, acoustic analyses of emotionally neutral sentences from a database of 41 talkers spoken both clearly and conversationally were analyzed in tandem with perceived emotion ratings for the same sentences to assess potential acoustic correlates of perceived anger in clear speech. First, principal component analyses were conducted to guide the selection of acoustic measures for statistical models. Zero-inflated mixed effects regression models were then conducted separately for temporal and spectral acoustic measures. Decreases in speaking rate and increases in temporal fluctuations in amplitude centered at 2 Hz (i.e., the word-level), both of which are prominent features of clear speech, were both associated with increases in the degree of perceived anger. Increases in fundamental frequency variability, another common feature of clear speech, were associated with increases in the perception of any amount of anger, but only in conversational speech. The results suggest that speaking rate, amount of word-level amplitude modulation, and fundamental frequency variability could possibly be manipulated to decrease perceived anger in clear speech.