Why do people make noises in bed?

Many primates produce copulation calls, but we have surprisingly little data on what human sex sounds like. I present 34 h of audio recordings from 2239 authentic sexual episodes shared online. These include partnered sex or masturbation, but each recording has only one main vocalizer (1950 female, 289 male). Both acoustic features and arousal ratings from an online perceptual experiment with 109 listeners recruited on Prolific follow an inverted-U curve, revealing the likely time of orgasm. Sexual vocalizations become longer, louder, more high-pitched, voiced, and unpredictable at orgasm in both men and women. Men are not less vocal overall in this sample, but women start moaning at an earlier stage; speech or even minimally verbalized exclamations are uncommon. While excessive vocalizing sounds inauthentic to listeners, vocal bursts at peak arousal are ubiquitous and less verbalized than in the build-up phase, suggesting limited volitional control. Human sexual vocalizations likely include both consciously controlled and spontaneous moans of pleasure, which are perhaps best understood as sounds of liking rather than signals specific to copulation. [ABSTRACT FROM AUTHOR]