YES!
You must have very sensitive hearing, like me. (I can hear the UPS truck from several streets away and my friends think I must have psychic powers. 😀)
Reading up on it, it seems to stop when the HomePod goes into sleep mode, which should be around eight minutes (though it normally seems longer).
It is a very very slight noise, and I now realise that my other speakers do it too. I've only noticed now because this is the first time I've had a speaker, i.e. the HomePod, on my bedside table (so very close to me at night when not in use).
Hopefully a software update could improve this.
[Cue a barrage of comments saying "mine doesn't do this" or "mine is silent" - this is a really subtle noise that you wouldn't hear if for example you have a hard drive anywhere in the room, or a DVR with a fan, and so on...]