It's coil whine. It makes much more sense when you realise that the 16kHz or so frequency is well out of range for anyone over 40. Many things related to noise

It's coil whine. It makes much more sense when you realise that the 16kHz or so frequency is well out of range for anyone over 40. Many things related to noise make sense once you realise all older people are near deaf, compared to the hearing of a 10 year old.