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 February 15, 2006 Loud Commercials RevisitedAnyone who writes for the print or Internet media sometimes gets an inkling that something published is causing grousing in cyberspace. Recently, within the space of a few days, I received two e-mails taking me to task for something that appeared in this space almost four years ago. In August 2002, I wrote a piece ("Loud TV Commercials a Matter of Signal Processing") that explained in simple terms (maybe too simple) why television commercials are often louder than the programs they are inserted into. In response, Rodney Lay wrote, "I have owned my own recording studio, was a disc jockey for six years, and was a session musician in Nashville for 20 years. This article is bogus. Limiters will produce a uniform level on all signals run through [them]. There is no excuse for ‘hot’ commercials during any program broadcast." Mark the Cyber-Shark wrote, in part, "For years I have abhorred the increased volume levels of TV and radio commercials. . . . I finally got sick enough of it to surf the Web to see what I could learn about this dubious practice and I came across your page on the subject. I must say, your explanation looks good on paper but is totally false as evidenced by my real-world experience. . . . All commercials I experience are definitely higher in volume than the entertainment they support! . . . I am a musician, and I am quite familiar with the use of compression and limiting to maximize the quality of an audio performance, whether live, for recording, or for broadcasting purposes. The higher volume of commercials is far more than the result of a difference between compressed and non-compressed ‘peaks and valleys’! . . . This is a real difference in volume, not a ‘perceived difference,’ as you state. . . . Can you seriously maintain that the commercials are not any louder than the entertainment, when everyone around you can plainly detect otherwise? Dunno where you came up with this goofy subterfuge, but it is not at all the truth." For all their vehemence, these gentlemen are basically wrong, despite their professional involvement in audio. Sure, there is plenty of sloppy broadcasting out there, where somebody isn’t watching his levels carefully enough. And because stations rely on auto-gain circuits to smooth things out at the transmitter, a signal provided to the cable or satellite company directly rather than over the air won’t benefit from such processing. But, for the most part, the effect is simply a matter of psychoacoustics. As anyone who has ever made a recording knows, the ideal is to adjust the level so that the peaks are as high as possible without going "into the red." This will be high enough to minimize noise, but not so high as to cause distortion. But that has to do with audio peaks, which form a tiny portion of any audio signal, and don’t contribute to our sense of loudness. That is a function of the average level, which is many decibels below those peaks. If the signal’s dynamic range is reduced through compression, or the tops of the peaks are simply chopped of by a limiter, the whole works can be turned up. The processed signal will still peak at the same point, but the average level of the signal will be higher and the sound will be louder. That’s not an illusion -- the sound really is louder. In this case, perception is reality. The problem arises when different signals have different levels of compression; commercials typically are heavily compressed, while program material is usually less so. Also, already-compressed commercials can be re-compressed as part of a station’s overall signal processing, which can exaggerate the effect. I don’t believe that there’s a conspiracy on the broadcasters’ part to curry favor with the sponsors by goosing the level of their ads -- it just happens. But that’s not to say it isn’t annoying. ...Ian G. Masters
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