There was a TV out a while back (don’t remember the brand) that was being sold on the basis that it moderated the volume of commercials in relation to the programming. Don’t know if it worked but have not seen it advertized in quite some time.
I have not done any TV shopping lately, so I can't say who else might have it.
Although it may seem simple enough, there are problems inherent in accomplishing this goal, and there have been previous efforts to provide relief.
Advertisers claim that it’s not absolute loudness that’s to blame. In other words, the peak amplitude doesn’t exceed the loudest parts of the programming in which their ads appear. But they rely on compression for the duration of their ads, which greatly increased the average amplitude and results in seeming like they’re shouting. Given that many commercials feature spokespersons speaking excitedly, it does seem like they’re yelling.
Some TVs, and even some cable boxes, have compression that can be enabled so that you can try to ‘even out’ the volume between commercials and other programming. However, some find this limiting, because you’re changing the dynamic range of the material.
Dynamic range — the difference between soft and loud parts — is important in conveying a director’s or musician’s emotions and dramatic intent. This is especially important in theatrical movies and classical music, where there is often a very wide dynamic range.
I used to wonder why it annoyed me when my wife was watching a movie on cable while I was trying to go to sleep, but that listening to a radio talk show didn’t have the same effect. It’s because of that dynamic range — there are very quiet and very loud parts in most movies. Talk radio stations usually use compression to keep voice levels reasonably constant. (although Mark Levin is a challenge — he alternately mutters at low volume, and then blurts out “There, I said it!” at a much higher volume. Hard to go to sleep with that going on...)
Using compression or automatic gain control to flatten audio to a consistent level can be done quite easily, but it can affect the viewing experience in a negative way.