Speakers Intermittently go quiet and crackle, then sound comes back. HELP!

[h3hl33t]

So, I was driving my 2001 Alero one day listening to the radio and all of a sudden I hear nothing. I honestly thought that the station went off the air, but after 10 min or so, I started to fool with the radio and it appears that the radio unit itself was working fine, just no sound coming from the speakers, only a sporadic crackling noise. This went on for awhile and now it seems like the sound from the radio will cut in low and eventually get higher, work for awhile, and then stop working and go back to the crackling noise. I also want to mention that the dinging noise when you push the lock button does not go off when the radio is having this issue, which leads me to believe there is something wrong with my speakers or something. I haven't done anything modification wise to the car, could it be the 100+ heat we are having in the midwest? Any help would be awesome.

Thanks!