Bless You, Dolby: Technology Limits Annoyingly Loud TV

Why are commercials so loud? The answer is extreme dynamic compression: the difference between loud and soft (the dynamic range) is compressed, and then the overall level is boosted, so that the average level is higher.

A compressor (or compression software) is a variable-gain amplifier. You can use it to make audio seem unnaturally loud. First, you set a threshold level, above which gain will be reduced (i.e. the level will be turned down):

Then the compressor reduces the gain of peaks that are above the threshold level:

Now, since the peaks have been reduced, there's headroom to boost the overall level higher than it was before - note how more of the signal is now above the threshold level:

There are many pleasing uses of compression, but it tends to abused in commercial soundtracks, and, increasingly, in pop music. And digital technology has enabled even worse abuses, because "intelligent" compression algorithms can control levels much more effectively than can analog hardware. Humans can hear a dynamic range of roughly 120 decibels, or dB. But it's not uncommon now to encounter recordings that have an effective dynamic range of just the few dB that press up against maximum level. (My graphics above show moderate compression - these days a lot of audio files look solid horizontal swipes from a broad paintbrush.)

People have complained about loud TV commercials for years. The response has often been that technically, commercials are no louder than anything else on the air. The FCC even supports this argument is a section of its web site (which they say is being updated - and, I hope, corrected):

Loud Commercials. In surveys and technical studies of broadcast advertising, we have found that loudness is a judgment that varies with each listener and is influenced by many factors (such as an announcement's content and style). We have also found no evidence that stations deliberately raise audio and modulation levels to emphasize commercial messages.

As whoever wrote this must know, the claim that commercials are not louder is only true in an artificially narrow sense. The peak levels of commercials are no higher than the peak levels of program content. But the average level is way, way higher, and that's the level your ears care about. If someone sets off a camera flash every now and then it's one thing; if they aim a steady spot light into your eyes it's another, even if the peak brightness is no higher.

Unfortunately, extreme compression is a classic arms race: if you back off your use of compression, you are in effect the first to drop your guns, and everyone else's audio will now sound "stronger" than yours. The psychological impact of volume is nothing to be sneezed at. I'm convinced it goes all the way back into primate pre-history, when the gorilla with the biggest chest and loudest voice was quite likely the boss.

But now it could be that Dolby's technology will remove the incentive to compete, by outsmarting all that intelligent compression. Oh, please...

Meanwhile, all we have is this how's-it-working-for-ya-so-far advice from the FCC:

Broadcast licensees have primary responsibility for the adoption of equipment and procedures to avoid objectionably loud commercials. You should address any complaint about such messages to the station(s) involved. You should identify each message by the sponsor or product's name and by the date and time of the broadcast.

Thanks to Peter Drescher for the link the San Francisco Chronicle article.