2003 voyager airbag/speaker problems

[hrslvr]

my 2003 voyager is having problems with the speaker system. they fade in and out, like one side has the volume being turned down on it, and when it does it, i get a slightly staticy noise. Also the airbag light is weird. It comes on initially like it is supposed to, however, sometimes it doesn't go off at all, and then sometimes it goes off and stays off, and then still sometimes it flashes on, stays on for 20-30 seconds, goes off for about 5-10 and comes back on again. I had it serviced because of a recall, and asked them to check these problems, the dealership told me there was no problem. Any ideas on what this could be?
Thanks for any help you can give me. I don't want to be driving down the road and have the airbag go off on me.