TV commercials sound louder than TV programs?

[NOLA MPx Fan]

Originally Posted by geostar";p=&quot

They do it so u notice them more. its the same here in the uk. but my tv has "auto volume" which automatically adjusts the volume so the sound is always at the same loudness.

My PVR has a skip forward feature. Haven't actually watched a commercial in something like 3 years.

[Dude1]

Yep they are louder because they use a limiter. This is basically a bit of software that will not let any sound go beyond a particular limit. If you keep turning up your amplifier it will eventually distort (unless you have a very good amplifier). The limiter puts a limit on what sound can come out, so it will never distort. Then, they record the sound as loud as they like, knowing that the limiter will cap it at the maximum possible.

Do what I do -- use the mute key when the averts come on.

[bruffterman]

Commercials seem louder because of something called "dynamic range compression" It's a kind of hard to understand but I think what happens is that somewhere during the broadcast chain, there is hardware which asses the audio signal and normalises the signal to some extent, to make sure that everything is delivered to you at the same volume. Commercials subvert this to make it sound louder by compressing the dynamic range of the audio.

The dynamic range we can perceive is typically 20Hz to 20,000Hz with the high end dropping off quite rapidly with age (16,000Hz is usually the maximum when you're about 25) But most of the sounds we hear are around 1000Hz - 6000Hz, with human speech being typically around 3000Hz (that bassy buzzing sound you can hear when you crank your amp right up with no music playing, is 50 or 60Hz depending on where you live - it's the sound of mains electric)

As such, our ears are specifically tuned to hear that range of frequencies best, and so we hear them the loudest, very high pitched sounds, and very bassy sounds, we hear much much quieter, until we cannot hear them at all (subsonic and ultrasonic). This is why your subwoofer is rated at about 50w and your drivers are rated at about 4-6w because it takes much more power and amplification to make those sounds, seem loud enough.

It's also part of how mp3 works, the end ranges of the spectrum are much more heavily compressed because you can barely tell the difference - if you still have good hearing you might notice the cymbals on your mp3s sound kind of "swishy" like water.

Anyway, as far as I can gather, the normalisation hardware doesn't take perceivable loudness into account when analysing the audio, but instead measure across the full dynamic spectrum. so the marketing company can squish the audio frequency range pushing all the sounds towards the 1000Hz - 6000Hz range that we hear best, and leaving the rest of the 20-20,000 range, silent. on paper the audio seems the same volume (or possibly quieter, i'm not sure) but to us it seems much louder.

I think the reason they do it, is because probably at least half of us get up during the commercials to go to the toilet or put the kettle on etc. so the idea is to make sure we can still here it even in the next room.