Quote:
Originally Posted by mrlizard
if you have two microphones on a source and you invert the waveform 180 degrees its gonna sound drastically different to shifting the phase.
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OK, I'll try to illustrate this.
Imagine the bottom two waves shown are the signals from two microphones.
In the left-hand example the two waves are in-phase and combine to create the wave at the top (the same sound twice as loud), and in the right-hand example the two waves are out-of-phase and combine to create silence.
In the right-hand example, the top wave of the pair at the bottom could be gotten by reversing the polarity one one of the microphones, in effect
inverting the waveform. But imagine instead of turning the waveform upside-down, that you slid the original wave sideways, until the peaks on one wave lines up with the troughs on the other. You would end up with the same result as inverting the wave, except this time you would have
shifted the wave by 180 degrees. This is why a 180 degree phase shift is regarded as the same as inverting the polarity of a wave.