Affective responses to the acoustic features of sounds from a Polyvagal Perspective
Our nervous system is continuously being stimulated by the acoustic environment in which we live. While we feel calm and safe while listening to some sounds, other sounds alert us to danger or life threat. Some responses to sounds are learned through associations with negative and positive experiences, while others are “hard-wired” into our nervous system. The acoustic features of sounds that trigger these hard-wired reactions has been described in the Polyvagal Theory (Porges, 2011; Porges & Lewis, 2009). Polyvagal Theory proposes that, prior to associative learning, subjective responses to sounds are neurophysiologically and anatomically dependent on features of the acoustic signal such as pitch and variations in pitch. Consistent with the theory, safety is signaled when the pitch of an acoustic signal is modulated (pitch varies across time) within a frequency band in which there are no very low or very high frequencies. The modulation in vocalizations is frequently called prosody and within the context of Polyvagal Theory is assumed to be the vocal conduit that humans use to express positive emotional states. Thus, a monotone signal lacks prosody and is not sufficient to signal safety. In this study, we examined how acoustic properties related to pitch modulation differ among body sounds, natural sounds, and music. In addition, we investigated how specific acoustic features relate to feelings of pleasure and arousal.
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