tv audio

Having an issue, when the tv goes to a commercial, or comes back from a commercial.  I will hear the sound twice, the only way to get sound back to normal is to change channels or if watching something on the dvr, exit and restart the program then the sound goes back to normal.  Not using any sourround system, just the tv.  Any ideas what to do to fix?  I have unplugged and restarted the box and doesnt seem to make a difference.