Simple Explanation

When two or more speakers work together closely and their sound waves combine, making them behave like one bigger speaker.

Concise Technical Definition

The constructive interference of sound waves from adjacent drivers reproducing the same signal, resulting in combined acoustic output behaving as a single, more efficient source—especially when spacing is within a fraction of the wavelength.

Layman-Friendly Analogy

Like two people pushing a swing at the same time and rhythm—each push adds up, making the swing go higher.

Industry Usage Summary

Used in loudspeaker array design, subwoofer placement, and line arrays. Engineers exploit mutual coupling for increased output, especially in low frequencies. It also plays a role in understanding array behavior and phase alignment.

Engineering Shortcut

Close spacing (≤ ¼ wavelength) + same signal = mutual coupling (adds SPL, acts like one driver).

Full Technical Explanation

Coupling or mutual coupling describes how two or more transducers interact when reproducing the same signal. If the acoustic centers of the drivers are sufficiently close (typically less than one-quarter of the wavelength of the reproduced frequency), the sound waves add constructively. This causes increased sound pressure level (SPL) and directional reinforcement. It is especially useful in subwoofer design, line arrays, and when designing speaker stacks to maximize output and minimize destructive interference.