Both acoustic intensity and loudness contribute to time-series models of perceived affect in response to music

In the fields of music and emotion, investigations of causal relationships between acoustic and perceptual parameters have shed light on real-time factors that underpin affective response to music. Two experiments reported here aimed to distinguish the role of acoustic intensity and its perceptual correlate of loudness in affective responses to a diverse set of musical stimuli (Western classical, electroacoustic, and synthesized single-timbre). This was achieved by first subtly distorting the inherently strong psychophysical relationship between loudness and intensity using synthesized reverberation, and then analyzing the consequences of this for perceived affect. Two groups of participants continuously rated loudness (N = 31) and perceived arousal/valence (N = 33) in response to 3 musical stimuli ranging between 2 and 3 min in duration. Each stimulus consisted of 3 continuous segments with 3 manipulations of the second segment: (a) original acoustic profile; (b) reverberation introduced to decrease loudness but with the intensity profile of the original version closely maintained; and (c) reverberation introduced but the intensity profile increased by a mean of 3 dB SPL. We hypothesized that intensity and loudness both make a significant contribution to time-series models of perceived affect. Four types of time-series models are presented: the first allows intensity but not loudness as predictor, the second allows loudness but not intensity, the third allows intensity and loudness, and for conditions of reverberation, the fourth allows for the impact of segment variation. In sum, time-series modeling shows that both intensity and loudness are predictors of perceived arousal and, to lesser extent, perceived valence. However, loudness is often more powerful and sometimes dominant to the point of excluding intensity.