Used Cars

Even after Federal legislation, TV commercials are still "louder" than TV shows. I put "louder" in quotes because that's not actually true. You see, there is a maximum recommended volume that commercials are supposed to stay within, and for the most part they do.

 

So why do they sound so much louder? Because of something called "dynamic range compression". By compressing the dynamic range, which is the loudest sound minus the quietest (just above the "noise floor") sound a system is capable of reproducing you effectively raise the apparent volume of the sound without breaking the upper volume limit. Quiet sounds get louder and loud sounds get quieter but the result is that everything sounds louder to our ear.  It's a very old technique, used in most rock and pop recordings to some extent, especially when it will be played back on cheap equipment that cannot reproduce a large dynamic range, or in noisy environments where the low-volume components would be overwhelmed by background noise (such as in a car or mall). Or any other time you want the sound to seem louder at the expense of range.

 

The dynamic range of a cassette tape is about 65 dB. Vinyl albums are somewhere around 68 dB. A Compact disc can do about 96 dB which is why CDs can sound both louder and quieter than an album. Note that each 6 dB is a doubling in possible sound amplitude. Blu-ray discs can have a huge dynamic range, north of 144 dB, which is far more than the dynamic range our ears are capable of receiving. Imagine being able to hear the quietest hint of a shadow of a whisper followed by a sound louder than the inside of a jet engine. That's what Blu-ray is capable of, although I doubt many people have audio systems that can reproduce that kind of range.

 

Too much compression of the dynamic range is therefore bad because you lose the natural volume peaks and valleys that live sound contains. But I'm guessing Barney's Used Car Emporium doesn't care much about that.