When a peacock shakes his tail, it produces a sound that is so low-pitched, humans can’t hear it. That’s despite the noise being about as loud as a car going past a few metres away.

Angela Freeman and James Hare of the University of Manitoba in Winnipeg, Canada have shown that peacocks can make these “infrasound” noises with their tails. The birds can also sense and respond to the noise.

“Humans don’t often think about infrasound as a potential signal, because we don’t perceive it,” says Freeman. “I think it’s more common than we think.”

Complete article: “Peacocks’ tails make noises too low for humans to hear“, Michael Marshall, BBC.