Is the volume regulated on TV channels?

Yes and no. The "no" part refers to the fact that you have a volume control on your TV (or in the remote control device), and you can make the sound louder or softer, or even mute it, if you want to do so. But the "yes" part refers to studies that have shown that some networks intentionally program their commercials to play louder than the rest of what's on the air. They're not supposed to, but it still does happen. All you can do about it is turn down the volume when these loud commercials begin to play.