have you noticed when some commercial comes on, the volume get a lot louder?

That used to be the case here; they deliberately compress the sound to make it louder, and so many people complained for so long that it's against the broadcasting rules to have ads louder than programmes.

Oh yes. Especially on TNT network. Commercials are what make them rich. They need you to pay attention

Yes its deliberately done.

I used to, then I found the normalization setting on my TV.

yes its soo my dad says that its due to the compression of the sound more compressed louder and he works for bbc soo I believe him to xxxjodie