sounds like a partially clogged vent.

How would I go about checking to see where the vent may be clogged? what's the best way or where wouldI start? on the roof? Please advise

yes, usually the vent will be almsot straight up from teh sink on teh roof. BUT it could in reality be plumbed halfway across the house.

if the vent is easily accessible, jsut take a water hose there and run it down in teh vent. push the hose as far down as you can, then turn onthe water full blast. it should push any debris on thru.

I also have a sink that burps & makes noise, but it does it at all hours of the day not just when used. Any guesses as to why?? Thanks.