It's called the Commercial Advertisement Loudness Mitigation Act, or CALM. President Obama signed it into law two years ago. The FCC spent months drawing up guidelines, and gave operators another year to comply.
Larry Kelley is an advertising professor at the University of Houston. He says before the CALM Act, there was a law that said the loudness of commercials, relative to programming, had to fall within a certain range.
"But that range was pretty broad. So advertisers were able to have their ads at a level that was, typically, at a level higher than program level."
Broadcasters have already invested millions of dollars in software and other equipment to normalize the levels between shows and ads. Kelley says even though the CALM Act is now official, most viewers probably won't notice a big change the next time they turn on their televisions.
"Most advertising really is at the program level as it stands. There are some that stand out. But, I think, for the most part, people won't really hear much of a difference."
The CALM act applies to commercial broadcasters — over-the-air, cable, and satellite. Non-commercial stations are exempt. The FCC does not monitor the loudness of commercials. But it will investigate listener complaints.