The excuse is goes something like this: 'prime time shows are recorded in multi-channel, and with full dynamic range. Commercials aren't typically recorded in such a fashion and subject to much more dynamic compression, so they have to be played louder.'
It's not that they
have to be played louder. It's that they sound louder when they're set so the peak audio level is set to be the same as the peak level for the program itself. This is what trips everybody up.
Commercial audio is compressed to sound louder, and it works. It's the same reason why top-40 radio is compressed, to sound "louder" than the competition. Do a google search on
radio loudness wars and you'll see what I mean.
For example - have you ever purchased a recording after hearing it on the radio, and when you get it home, it sounds quite a bit different than it did on the air? That's because the dynamic range was squeezed out by the compressor/limiter at the end of the station's audio chain. When the audio is compressed, the quiet portions of the sound are brought up to the same level as the loudest portions of the passage. This makes the audio sound much louder without actually increasing the peak level. It also increases the normally quiet breathing sounds of an announcer to the point that it sounds like they're gasping. And excessive compression actually causes listener fatigue.
It's an interesting psychoacoustric gimmick. It's also used by radio stations to bring the quietest portions of the audio above the rumble of road noise in your car.
The exception to this broadcasting rule is most NPR and classical music stations. They generally don't participate in "loudness wars" and they're more interested in preserving the dynamic range and expressiveness of the music.
If I hear that the FCC is willing and ready to address the issue of compression, I will feel better that something is actually going to change for the better. However if they only address the issue of peak audio level and "dialnorm" settings, we'll still have commercials that sound louder than the programs.
/soapbox mode off