If you notice something different today while glued to your favorite TV show it could be this: a federal law that limits the volume of TV commercials went into effect today. The Commercial Advertisement Loudness Mitigation Act, known as CALM, applies to commercial broadcasters, cable operators, satellite services and other video distributors. Public broadcasters are exempt. The legislation, prompted by irritated consumers, was unanimously passed by the House and Senate and signed into law in December 2010. The FCC gave television stations time to implement the new rules.