S-10-whining-goes away at acceleration

Hi!
I have a 95 S-10, 4 cyl. 179,000 miles. Lately it has been making a noise, like a whining or high humming noise at the front of the car in idle, deceleration, even in park. Seems to only happen at lower speeds. When the accelerator is pressed the humming goes away. Only happens if car is warmed up or been running for a while. I opened up the hood and it seems like the noise is coming from the right side but it was kind of hard to tell. My husband said it sounds like it is coming from the middle. Help!