Originally Posted by paul54
Electrical signals may have a polarity. There is no such thing as "acoustical polarity." Acoustically there are rarefactions and compressions. The order in which they come is neither "correct" or "incorrect", but is determined by physics. Think of a one-headed drum. If it is struck from above, and you (or a microphone) are listening from above, the sound starts with a rarefaction; the head is sucking air away from the mic diaphragm and your eardrum. If you were BELOW the drum head, along with your microphone, the opposite would be true; the sound would begin with a compression, the air being pushed toward the mic and your ear.
Saying "punch" while inhaling is essentially doing the same thing: listening from the lung side of your larynx, or from outside. However, the example is misleading since the "punch" examples sound VERY different in reality. In my drum example, the difference is likely undetectable without looking at the waveform on a 'scope, and even then, you'd have to assume the electrical polarity of everything in the electrical path of the recording and playback process, including your speakers was in proper polarity, otherwise you might as well just flip a coin. Without other sonic clues, you wouldn't hear a difference.
I'm not saying that changing electrical polarity in a system is not audible. I AM saying that you can't tell which is "accurate" or "correct" unless you witnessed the entire recording process.
I use the term acoustical polarity meaning the end result ... what comes out of the speaker. As opposed to electrical polarity which exists only electrically; I must use test equipment to verify. A component can have correct electrical polarity meaning waveform in goes up, wavefrom out goes up, but this does not mean the end result out of the speakers will be in correct acoustical polarity. A system that has correct acoustical polarity will move the speaker cone forward for a "P" sound, not backward. As when someone speaks a "P" the compression is what comes first. I do not have to know anything about the entire recording chain to get a system to reproduce correct acoustic polarity. I just have to listen. In this case two wrongs do make a right.
If something is recorded with incorrect electrical polarity, I can correct it by flipping the electrical polarity which will then get the acoustic polarity (what I hear) correct. Or correct it in software which is what I do with my CD compilations.
As far as listening to the drum from one side or the other, not sure I agree with what you are saying although it makes sense. I am not sure that this is correct model or even that my model with the "P" is as it is the same thing except that I don't think I will ever listen to someone while inside them or a recording with the microphone inside them.
I will just say that I can hear correct polarity with drums quite easily. Snare perhaps easiest. One way sounds like what a snare drum sounds like in person, the other way doesn't. Although these differences are not large, I have done quite a bit of testing here and am getting to the point where I can tell when something is out of acoustical polarity without any comparison.
Inverted polarity does have an overall effect that can be heard. Now when I test, I tend to use the voice and will key in on p's or s's. etc. Movie soundtracks, listening to the background noise is easiest. Traffic noise, wind, rain, crickets. I listen to dubstep and with a lot of this, when the polarity is incorrect, things stop floating around and will not come in out. The whole sound just loses life and flattens. I can very easily here correct acoustic polarity when I record just me speaking.
There is a line in Animal House something like, "It's time to take the bull by the balls and kick those punks of campus." Correct acoustic polarity with this line and I laugh everytime, incorrect and I do not laugh. It is quite easy to hear the difference. The b's and p mainly. It is the delivery of the line that is so funny. And when it is out of polarity it loses the humor as the humor is in the voice. How he modulates the air pressure. Once again, not sure if pressure is the correct model. I just know that you can make the sound unnatural by inverting the polarity.
Record a one headed drum and play it back and one polarity will sound more like what I hear if you actually play the drum. I do not care which side of the drum you put the mike on, one polarity will always sound more natural than the other.