Noise coming from under the hood intermittently

What sound?
Maybe a pump

 

There are several sounds that can fit that description. If you can post a recording, that helps, or you can search for other similar threads where other people posted recordings, and notice which of those sound like yours.

 

The gasoline engine? LOL

 

What is the sound that OP is not going to describe? Lol... I think its a trick question!

If a car makes a sound and the person who is hearing the sound doesn't describe what the sound actually sounds like to people on PriusChat, does the car really make a sound?

 

Well, the OP described when it happens, which I guess is the easier part to put in words, without trying to do the "well, it's kind of screechy, with a little bit of whong-ong-ong-ong, only not as buzzy as that" kind of thing.

If there were only one gen 2 Prius sound that could happen at the times described, that might be enough to ID it.

Trouble is, there's more than one. So posting a recording is more helpful, or listening to the recordings from other people's older threads to pick out which one it sounds like.