Simple Explanation

The reduction in signal strength or volume after it hits its peak.

Concise Technical Definition

A gradual decrease in amplitude or energy of a signal immediately following its peak level.

Layman-Friendly Analogy

Like the echo of a shout slowly fading away in a canyon.

Industry Usage Summary

Used in audio, music, and signal processing to describe how sound diminishes over time after the initial peak — such as the length of time a note fades after being struck.

Engineering Shortcut

Measured in time and level; often modeled as an exponential falloff.

Full Technical Explanation

In acoustics and signal processing, "decay" refers to the drop in amplitude of a sound or signal after it reaches its peak. This stage follows the attack and precedes the sustain phase in an ADSR (Attack-Decay-Sustain-Release) envelope. Decay influences perceived clarity and space in audio — fast decay makes a signal sound tight, while slower decay gives it lingering presence. It's especially important in reverb, musical instrument response, and sound design.