How can destructive interference reduce or cancel sound?

In the context of acoustics, destructive interference occurs when two or more sound waves overlap in space and are "out of phase" with one another.12

Specifically, this happens when the crest (maximum pressure) of one wave coincides with the valley (minimum pressure) of another. Because of the principle of superposition, the resulting disturbance is the algebraic sum of the individual waves. When these waves are out of phase, their opposite vibrations effectively subtract from each other, reducing the amplitude of the combined wave. If the waves have equal amplitudes, the destructive interference results in complete cancellation, leaving the net disturbance to the medium at zero.123

This principle is utilized in various technologies to reduce noise:
* Electronic Mufflers: These devices sense engine noise and generate a matching sound wave with the opposite phase, causing the two to cancel each other out.2
* Industrial Noise Control: Systems can electronically reproduce ambient noise in reverse phase to reduce overall sound levels in a workspace.2
* Speaker Setup: Proper wiring ensures speakers are in phase; incorrect wiring causes destructive interference, particularly at low frequencies, which attenuates bass.2