All stations in your area are not likely to have a problem at the same time. Plus they would fix it asap.
It's not a reception problem.
DTV is a data stream. You either receive the data stream or not and it contains both picture and sound, not like the old days when they were separate transmitters.
It is either you decoder box or a cable going to the TV.
One thing to check is tune the TV to some channel and if it's an older one you should hear static. Some of the newer even analog TV's though mute when there is no signal.
Also most converter boxes have a volume control on them as well. So make sure it's turned up as well as the sound on your TV.
