The days of unexpectedly loud TV commercials are numbered thanks to a bill that has just passed the US congress.

The tenuously-named Commercial Advertisement Loudness Mitigation Act (that is, CALM) tackles a problem that dates back to the beginnings of commercial television and has attracted attention on both sides of the Atlantic: that the commercials are so much louder than the programming.

The bill passed the Senate unanimously in October. The House of Representatives had already passed a similar bill, and has now backed the Senate version, which had only minor differences. The bill has now been passed to the President for signing, which appears to be a formality.

The main measure of the law is to give legal force to previous voluntary standards agreed by the Advanced Television Systems Committee, which develops the technical standards for digital broadcasting. These only cover the means by which networks measure and control volume.

The actual volume limits will be determined by the Federal Communications Commission, which will have 12 months to set the new rules. It appears the most likely option is that the maximum volume of a commercial will not be allowed to exceed the maximum volume of the programming that preceded it. That suggests any advertisers that do want to make the maximum impact should try to find out which networks are planning to play Bjork videos.

Once the FCC makes its rules, TV stations will have a further 12 months to comply, though there’ll be exceptions for those who would suffer excessive financial hardship.