Most likely the problem is an audio setting in the TV or a set top box if you use one.
How do you get TV, is it cable, satellite, or antenna?
If cable, do you use a set top box or does the cable come from the wall and screw into the connector on the back?
If you use a high def cable box, are you using the 5 wire component video connection between the box and the TV, or are you using HDMI?
OK, is this a Motorola cable box from Comcast?
Hmm, OK, I would need the model number of the box to provide any specifics, but what the problem most likely is is that in the set up menu of that box, there will be a HDMI audio option that will most likely be labled "PCM Audio." If you find that and can set it to that, I'll bet that will take care of your problem.
What's happening is that the HDMI audio that your set is receiving is designed for a surround sound audio system. The dialog for TV programs is supposed to come out of a center channel speakers, and the background music is supposed to come out of the left and right speakers (and also, the rear speakers). If you don't have a center channel audio speaker, you keep trying to turn up the sound to hear the dialog, but then when the music comes on, it's blaring loud. If you can set the box to deliver PCM (or "Puklse Code Modulation") audio, that should strip the audio of the 5 channel encoding that I'm guessing you now have.
See if you can find a setup menu and if that audio setting is there. Let me know if you have other questions or run into problems, and thanks for using JustAnswer!