Originally Posted By: benjammin


As for audio signal level during commercials, if it is just compression, why is my db meter reading twice the signal level during commercials? Sound power is sound power, and it doesn't matter if you are feeding audio fidelity at 10 Khz if the majority of the audio is voice because the power band for voice is less than 5 Khz, so the only way the voice audio level goes up is if someone is jamming the gain over 0db. However you want to put it on the front end, the result is a matter of fact that audio for commercials on some channels is twice the power level at the tv output as what it is during the program. I would bet good money if I put an O'scope on the audio signal in my tv set that I'd see the peak voltage significantly higher during the commercial than during the show. Also having worked on commercial broadcast equipment, I've seen plenty of examples where the rf signal has been overmodded and in fact has bled into adjacent channel space. How does that happen if the audio input isn't being overdriven?


Well you and I both know that overmodding a commercial Xmit site is against FCC rules, esp when you start slamming adjacent channels. But the audio portion of the programming, was, at least in 1993, which was the last time I made a commercial for broadcast, clearly and specifically limited to 0db average, and we had stuff rejected for broadcast for over-modulation.

Now that said, even way back then - and more so now - there are astonishing tricks they can do with sound, especially with various modulation envelopes that mess with the phasing and frequency of the signal in a way that both pushes voice way forward - and as you may have heard in some of those care commercials where they mumble the terms and conditions disclaiming the previous 28 seconds of offers, "smearing" the voice into music via a digital process that "averages" sounds together similar to the way a digital imaging tool can average images.