Weird Noise at around 2000-2700RPM

[rawb_dbap]

Hey guys , so I started noticing this noise after I took my car to the AC mechanics. They recharged my system (leaked everything out 2 days later though) and maybe an hour later I started hearing it. It sounds like a whistle at 2000-2700k RPMS. At first I thought it was a belt, but it does not sound like a belt at all. When I reach 2000 RPMS I play with the gas and it whistles every time I tap it at those RPMS also... What could this be? Is it a serious fix? Thx guise.

[Nokomp]

Being a cb7 owner your gonna have to learn to get under the hood and find the noises, its nearly impossible to pin point over the internet. in this case move the throttle by hand and listen... i smell a bad ac compressor.