I have 2 '01's and they both started this at around 200K and its only when under a slight load, such as AC and goes away once past 1/4 throttle. lots of freeway noise in the background, sorry. I am pretty sure its not belts and the car runs amazingly. Check engine light is due to my lower O2 sensor (header) and not anything major.
Any ideas would be wonderfull.
Oh, and BTW- stock transmission- no problems! I dump the fluid every 30k since I bought it new.

 

its your belt ... tighten it

 

your engine belt. check it for cracks or flex and get a new one if it looks worn

 

200,000 miles? Timing belt should've been serviced by around 100,000.
Inspect it for wear.

The o2 sensor, you should go on RockAuto and order a new one and get a bung welded into that header, because damn do they actually make an effect and toll on a Civic.

 

Make sure your power steering resevoir is full. My pump will whine if its not filled properly.

 

Sounds like a Bad a/c condensor

 

tightened the belts, and all the belts are new. It also made the noise prior to new belts. noise still there on both of my civics, more so on this one-it does it with or without the ac on. its caused by throttle rather than rpm or accessory load that normal belt squeal suffers from as It does it between zero and 1/4 throttle only, where belt squeal is normally at low engine rpm with high alt or ac load. Next up is pulling the alt and ps belt off and see if the noise is still there- in real life it almost sounds like a leaking EGR valve or something.