In the USA since 2010, there have been standards that prohibit ads being louder than the program material:

https://en.wikipedia.org/wiki/Commercial_Advertisement_Loudn...

Nvidia shield can do that, they call it "nighttime listening mode" or something, I leave it on permanently, much better experience.

Here’s a DIY project to make a TV volume limiter, I haven’t done it myself but it looks cool: https://www.youtube.com/watch?v=j1V2I-otdzk