On Wednesday President Obama signed into law the "Commercial Advertisement Loudness Mitigation" or "CALM Act." A press release from the White House states the law "requires the Federal Communications Commission to prescribe a regulation limiting the volume of audio on commercials transmitted by television broadcast stations, cable operators, and other multichannel video programming distributors."
The House passed the bill by a voice vote on Dec. 2. It was passed the Senate unanimously in September. The FCC will start enforcing the new rules within a year.
Consumers have complained to the FCC about loud commercials for decades, and Rep. Anna Eshoo (D-Calif.) told the Wall Street Journal in December that the CALM Act is the most popular piece of legislation she's sponsored in her 18 years in Congress. "If I'd saved 50 million children from some malady, people would not have the interest that they have in this," she said.
For now, the FCC has a webpage on the subject, which advises consumers, "Manually controlling volume levels with the remote control remains the simplest approach to reducing excessive volume levels."