(1) The condition where the connection in one channel of a stereo signal are reversed. This is most likely to happen at the loudspeaker, and results in phase cancellation, particularly apparent in the bass.
(2) In electronic signals, changing the polarity of the signal from positive to negative or vice versa, thereby causing a reversal in polarity of the signal. When viewed on an oscilloscope, the waveform flips with respect to the time axis. Also called polarity reversal or phase inversion. See common mode, out-of-phase. The pair of loudspeakers on the left are in phase–the speaker cones cause compression and rarefaction the surrounding air in unison. Those on the right are out-of-phase, causing the air compression generated by one speaker to be cancelled by the rarefaction generated by the other.
