Ever hear your friend’s stereo system and thought “I don’t remember this song sounding like this before”. Maybe it sounded like it was playing through a tunnel or some of the instruments sounded louder than you remember hearing on your own system. Well my friends, you may be hearing the sound of the music “out-of-phase”.
We all know that sound is just vibrations that cause mechanical frequencies that funnel through the ear and vibrate the eardrum which then is converted to electrical signals which the brain processes as sound. The timing of the vibrations of each frequency can change depending on many variables from the physical listening space to how the sound was recorded as well as the playback device, be it loud speakers or headphones. On a home audio system, you can flip one of the speaker wires, stand back and listen to the flat or strange sound you end up with. Sometimes, when listening to a movie you may lose some of the dialogue as a result of out-of-phase sound.