Jacek Kolacza, Gregory F. Lewisa, & Stephen W. Porges a,b
a) Department of Psychiatry, University of North Carolina
b) Kinsey Institute, Indiana University

Summary: “… The Polyvagal Theory proposes that subjective responses to sounds are initially (before associative learning) based on two features of the acoustic signal: pitch and variation in pitch.

The theory articulates that for mammals there is a frequency band of perceptual advantage in which social communication occurs. It is within this frequency band that acoustic “safety” cues are conveyed…

… body sounds have a unique acoustic profile that may trigger hard-wired responses, which may be especially pronounced in individuals who are in a physiological state of hyper vigilance.”

You can see an update to this study here

And a more detailed synopsis and podcast from Dr Porges about his theory here