Specific point in a cycle, namely a sound wave in audio, measured from a zero point and given as an angle. Many powered subwoofers feature a phase switch allowing the user to change the phase from 0 degrees to 180 degrees (with 180 degrees being exactly one half of a complete cycle; a complete cycle is 360 degrees). When two audio signals are out of phase, they cancel each other out resulting in a weak signal (or no signal at all if they are 180 degrees out of phase). This occurs when one sound wave is at its peak while the other is at its bottom point, its trough. Similar to adding negative one to positive one, the end result is zero. By switching the phase, sound waves can be aligned with other sound waves so they reinforce one another instead of canceling each other out.