Engine noise in drive only
 

I have a 1997 honda accord 2.2 4 cylinder with 158,000 miles. It's developed a noise near the engine compartment that sounds like a low level tweet, as if blowing softly on a whistle. The noise occurs during acceleration after it's been shifted into drive. It does not occur when the car is in park, neutral or reverse. The noise seems to disappear after 100 yards or so, or maybe is obscured by road noise, I'm not sure. I tried belt conditioner but the problem persists.

belt conditioner don't do jack if the belts are loose.