I am reading a very interesting book “What the ear hears (and doesn’t)” by Richard Mainwaring.

Apparently very low frequency sounds, at the cusp or just below what we can hear can produce ghostly visions. This was discovered by NASA in the 70s. It happens because our eyeballs resonate around 19Hz and make us see things that aren’t there.

Everything, including every organ in your body, will resonate at some frequency. A furnace fan or even a passing vehicle might produce a sound that causes an odd feeling somewhere in your body.

Might be something like that. Fascinating book, by the way.