I noticed over the weekend this noise coming from what seems to be the head. I recently replaced the water pump myself. Everything has been fine for over three weeks. I am not sure what is causing the noise or where exactly it's coming from. I am going to take the valve cover off tomorrow and take a look around. My oil level has been fine ... actually I just changed the oil when I did the water pump. I have never over-reved the motor and it is still idling fine. There hasn't been a power drop at all either. Here's the small video I took:

Video (1.38 MB)

 

If it's a "chattering squeak", probably your T-belt tensioner.

Possibly your A/C belt tensioner, but it wouldn't sound like it was near your head...

 

Wow, thats a really weird sound. You might have more luck posting this in the Prelude forum. Some of those guys are H22 geniuses. Good luck.