Seems to be a real issue with the razr series. My wife's did the same thing after a call to verizon they made her do a factory data reset. After that didn't fix it I had to call them back to get a replacement.
Found this on another thread, and it solved my sound problem. Hate to do it once a day though, and don't want a factory refurnished either. (Not a typo,,,lol)
Originally Posted by MrGibbins
Its a hardware issue and has been posted in another thread like this one. Trying playing an audio file and while its playing turn the phone around and press along the top of the Kevlar back and on the top portion where the speaker is located. Sound should cut back in. My phone stopped having sound yesterday and I found that post and tried it. It works. Guess its a manufacturing defect or a result of the Kevlar being too soft and allowing pressure on the phone to break the connections. Others that have taken it in before the 14 day period said they were sent a refurbished instead of a new device. Not sure if I want to deal with that. Might go in today and see what they can do.