is it in the engine bay? or can you not pinpoint the sound?
If its up front, open your hood and turn the car on, listen near the belt. if it is at higher RPMs then grab the throttle body cable and rev it up a little until you hear squeaking.
It could possibly be the water pump so before you take it into a shop make sure you know what it is because the belt might not be squeaking, but rather one of the many components that it actually turns (ie water pump, alternator, etc..)
if you dont know what it is I actually just posted my own question about squeaks, it might help you out
Hope i helped!