I have a 05 997 with 8K miles and serviced regularly. Last month, I noticed a plasticky creaking sound coming from behind my head, down below a little. It almost sounds like the speaker, but examination shows no play (when parked). I'm wondering if it can be the seatbelt tensioners? It doesn't quite sound like it's coming from that high up at the ear level. The panel doesn't feel loose and I didn't do anything to the speakers ever. Anybody experienced this? Any recommendations?

 

Can you have someone cram themselves into the back seats and listen while you drive?