The noise depends on the pigs, on what they are bedded on, and how light a sleeper you are. Guinea pigs that are on pellets tend to be noisier than those on fleece. Some wheek and/or chirp in the middle of the night, other's don't. Some play with the water bottle at night, banging it into the cage. Others chew the bars. If you're a heavy sleeper you may not hear them. If you're a light sleeper, they'll keep you up.
The other issue is whether or not you have allergies. Even if you don't have a current allergy to hay, if you have other allergies, particularly respiratory ones, you may develop hay allergies.