I have a 16gb verizon iPhone 5. With iOS 6, and now with 7, even after a fresh restore, I still had intermittent sound issues. Mostly the notifications getting very low in volume after using Siri. But that's not the only time I have this problem. It just seems to come and go. It also affects the keyboard click volume. The only way I have found to fix it is to either reboot, or go into the music app, go to now playing, turn the volume slider all the way up, back out of the app, and SOMETIMES the volumes will be back to normal. Any fixes for this?