wsonny,
The sound could possibly be coming from your air cond compressor, or one of the aircond parts. I have that sound on my car too. Sometimes, I'll hear a wheezing sound when I accelerate and it would get louder if my rpm goes higher. The sound, if I open my car bonet and listen to it carefully, comes from something that uses a belt. My mech says it's the aircond compressor or something. You may want to try to listen to where the sound is coming from from your engine bay.