I've had something similar happen to me too…everything was just way too loud for some reason, even with ear plugs in. In my case, I wasn't hallucinating and my therapist thought it might have had to do with my anxiety and hyper-vigilance with sound. Basically, sound in certain circumstances seem to bother me and I guess I had a big freak out one day over it and then for a while afterwards, everything sounded too loud and I was afraid of sound for a while.

I can't answer for you whether your issues with sound are hallucinations or not, but I just wanted to say that they aren't necessarily in every case. Stress/anxiety could possibly do it too as it did in my case.