Why does the volume increase when a TV commercial comes on?

Dear Mr. Alice:

Why is it that when a TV commercial comes on, the volume is automatically raised to a seemingly ridiculous level? What is the network's position on this? Are there stations that will not use this practice? TV is my life. The only time I want the noise level altered is when I actually pick up the channel surfer and alter it!

-- Disturbed by the Voices, Kearny Mesa

Personally, that's one of the best things about TV-- watching the Fritos and beer fly as Cal Worthington blast Pa Alice out of a sound sleep in front of the tube. But to put this universal question to bed forever, we woke up Margie Baldwin of Channel 10's engineering staff and also checked with the feds. Here's the story. Nobody raises the volume. And I'll keep my voice down too.

According to the FCC, the first complaint about loud commercials was phoned in roughly two seconds after the first TV commercial was broadcast. That goes back into the 1950s. So now it qualifies as an official American tradition. And right at the top, we have to clarify the difference between volume and loudness. Volume is a measurable quantity, a specific amount of voltage driving a speaker or transmitter. Loudness, the thing about which you complain, is a person's subjective reaction to sound. Individually variable, hard to quantify scientifically. The FCC does have laws governing the maximum allowable broadcast volume, and TV channels can control volume, but the subtleties of loudness are tougher to corral.

Recording engineers have a bag of tricks for making commercial audio tracks sound as "full" or "dynamic" as possible without exceeding volume limits. According to Margie, techies call that a "greater spectral density." We call that a loud commercial. And it's well known to commercial producers that high-pitched, sharp, repetitious, or other aggravating sounds will be perceived as louder even when they're broadcast at the same volume. You might call it the Fran Drescher Effect. Assuming all cast members on her show are recorded at similar levels, we will hear her screeching and braying as louder just because of the shrill, fingernails-on-blackboard quality. And audio engineers will record commercials at the upper legal limits of the volume range, unlike program content, which is generally more variable.

There is a "loudness-control" device (Channel 10 has one, though they're not required by law) that can approximate the perception of the average human ear. It monitors the station's audio signal before it goes to the transmitter and can adjust the volume level down automatically for the most jolting sounds. But it's still just a machine, not a person, and each person's perception of "loudness" is different.

One last thought. Do you have a stereo TV? Maybe your speakers are wired up out of phase. That means you have to crank up the volume to hear monaural programming, but when a stereo commercial comes on, it melts your fillings.