[DonRotolo]

I'm not a broadcast engineer (but I play one on TV!) but I used to be, sort-of. I was on staff for a TV manufacturer, so maybe a Receiving engineer?

Anyhow.

Ed Barker has it right: These is some dynamic range compression going on, so while the regular programming has a relatively large difference between quiet and loud, the commercials have only 'loud', boosting the sound during 'quiet'.

The commercial 'loud' is no louder than the regular programming 'loud' (thus in compliance with the coming regulation) but the 'quiet' is also somewhat loud. Advertisers do have to be careful to avoid annoying their (potential) customers however.

If you have an oscilloscope you can monitor the waveform voltages and see this. Use the slowest timebase you have and try to compare programming to advertising..