By sound? Try tapping the plasterboard, where the stud is, it will sound less hallow. That is not precise, but will give you the stud location within a few inches. You can then make a row of holes, with a small screwdriver, to find the actual stud.
Another way, is to use a rare earth magnet. It will be attracted, to the plasterboard fixing screws. Confirm it, by finding more fixings, in a vertical row.