Here’s a Tom Scott video instead of a paywalled article

Ahhhh fascinating.

For years, I’ve been adamant that when I stir a cup of hot tea or coffee, the pitch of the scraping spoon almost imperceptibly shifts, and assumed it was because of the gradual slight cooling of the water. Nobody else could seem to hear what I heard.

Wasn’t sure if it was my music producer ears or imagination.

Always wondered about this. Article is pay-walled though.