No matter what you think you've heard, TV commercials really don't get louder than the programs they accompany.

Production tricks only make them sound like they do. It's called "inconsistent" or "perceived" loudness. Perceived or not, the problem likely will get worse with digital television.

The annoyance is real enough that U.S. Rep. Anna Eshoo is making a federal case of it. Fed up to her ears at being blasted off the couch by commercials, the California Democrat introduced a bill in Congress called CALM -- the Commercial Advertisement Loudness Mitigation Act. It would require the Federal Communications Commission to set standards to keep commercials from running at louder volume than the shows around them. A similar rule in England takes effect next month.

"There's been a shockingly lot of reaction," said Eshoo aide Jason Mahler, who noted that the bill quickly picked up nine co-sponsors. "It's all been favorable."

That's no surprise. The FCC puts "abrupt changes in volume during transition from regular programming to commercials" high on the list of complaints it gets from consumers.

"I particularly notice it on the Weather Channel, not only with commercials, but also during their 'Local on the 8s,' which blasts the local forecast," said Bonnie Kinkopf of Lyndhurst. "Instead of making us pay closer attention, it's an annoyance. I never think to hit mute; I just turn the volume down or change the channel."

Ann Zakelj of Willoughby Hills was equally specific: "If there's anything more annoying than pre-pubescent siblings hawking autos," she said, "it's pre-pubescent siblings hawking autos in decibel levels high enough to shatter a windshield."

But solving the problem -- or identifying it -- isn't as simple as it might sound.

Eshoo's bill tells the FCC to regulate a problem that does not technically exist -- but is an issue that engineers say could worsen when television goes fully digital in February.

"This is something that has gone on way too long," said Frank Foti, whose Cleveland-based Telos Systems Group essentially sets the standard for audio-processing equipment in radio. "People in Washington can do some bogus things, but in this case, they have a point, and it's something we can fix. The clock is ticking."

Why the ads seem louder

Commercials really aren't louder than programs. Because of limits imposed on TV signals, an ad can't be louder than the loudest part of the show with it. But going from, for example, a drama with hushed dialogue to a shouted commercial pitch introduces what is called "perceived loudness."

And perception can reflect manipulated reality.

"A TV program has a mix of audio levels," Eshoo said. "There are loud and soft parts. Nuance is used to build the dramatic effect. Most advertisers don't want nuance. They want to grab our attention, and to do this, they record every part of it as loud as possible."

That involves audio compression, which shrinks the range of sound in a commercial. Used frequently in radio, compression tends to boost softer sounds to the level of louder ones. Measured on a meter, it means that a commercial can have a higher and louder average sound level than a program while not exceeding the show's peak loudness.

The difference between the average level of a relatively uncompressed program and a highly "sweetened" commercial is noticeable. Inconsistent loudness is typically more pronounced with local ads and when switching between cable channels, which have a wide disparity of volume levels.

High-definition television adds more variables

Brooke Spectorsky, general manager of WKYC Channel 3, said there are also noticeable differences among digital, high-definition channels. Digital television has a wider dynamic range, or loudness spectrum, than analog channels, and networks haven't agreed on a common setting for digital audio.

"When it's done right, it's phenomenal," he said of digitally delivered sound. "But the complexities are significant, and the technology needs to catch up with it."

Channel 3, the only local station broadcasting full 5.1-channel surround-sound with HDTV, invested in volume-control equipment to normalize levels and deliver a more consistent signal.

Foti's Telos Systems Group is taking its first big step into television with loudness-control equipment. The group's Linear Acoustic Division already has installed it at a station reaching Eshoo's district in Silicon Valley, which feared losing viewers and revenue over complaints about inconsistent loudness.

Foti hosted a demonstration for the Cleveland chapter of the Society of Broadcast Engineers this month during a discussion about the need for audio equalizing with digital television. He said that properly equalized audio should keep viewers from straining out of their seats to hear whispered dialogue and being jolted out of them by sudden loud noise.

It also could keep the FCC from being told to regulate something it has so far avoided. The commission only controls peak audio signal and recommends viewers contact broadcasters or advertisers with other complaints.

In Britain, new rules from the Broadcast Committee of Advertising Practice take effect July 7. They require broadcasters to bring the "maximum subjective loudness" of ads into line with program levels and say that "advertisements must not be excessively noisy or strident."

Dan Jaffe, senior vice president of the Association of National Advertisers, said loud ads are "not high on the list of complaints" they receive, possibly because they don't deal with local commercials. But the group's technical committee is reviewing Eshoo's bill and the coming switch to digital.

"Clearly, advertisers are not trying to annoy their customers," he said. "They spend multibillions of dollars to try to effectively reach customers. Consumers are well-armed to respond if they don't -- to turn it off, turn the sound down or block ads completely."