I did a small experiment with a little python code. I generated two pairs of signals, for each of them the first being a square signal, and the second signal with the same absolute frequency spectrum but with different phase. I did the first one in a non linear way, by adding a phase delay of pi/2 for every other harmonics. I did the second pair in a linear way, by adding a delay of pi/2*(i mod 4), with i being the order of the harmonics.
The result is that non-linear phase distortion is clearly audible for a square wave, while linear phase delay is absolutely not audible. Why is it so? By what mechanism could human ear hear non-linear phase shift but not linear phase shift?
Here are a graph for both of them, each of them showing both a regular square wave and a phase delayed square wave.
Here are the respective audio files for both of them : audible phase, inaudible phase.
The result is that non-linear phase distortion is clearly audible for a square wave, while linear phase delay is absolutely not audible. Why is it so? By what mechanism could human ear hear non-linear phase shift but not linear phase shift?
Here are a graph for both of them, each of them showing both a regular square wave and a phase delayed square wave.
Here are the respective audio files for both of them : audible phase, inaudible phase.