IF a single note from a trumpet (say) is played, it will cause first, say, a compression, then a rarefaction, and so on. IF a speaker were reproducing that sound, in phase, it would first move forward, and then back. Out of phase, it would first move back, then forward.

Given the phase anomalies that exist in most real world environments, and the fact theat most PM is highly complex, abs phase has not been shown to be audible at all. Richard Greiner did do some studies that showed that i9n some very simple tiones, with a very clean environment, it si audible. However, that does not extend to real world listening of real world PM.
-akhilesh