1.8: Sound Envelope

Understanding Sound From Ear to Engineer · LibreTexts

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    From LibreTexts, under CC BY-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Sound Envelope

    A multi-colored graph showing attack, decay, sustain, release as part of the sound envelope.
    Figure \(\PageIndex{1}\): ADSR, Tobias R. – Metoc, (CC BY-SA 2.5; author via Wikimedia Commons)

    The sound envelope refers to the way a sound’s amplitude changes over time, particularly how it evolves from the start of the sound to its eventual decay. The envelope is often broken down into four stages usually expressed as ADSR:

    1. Attack: The initial onset of the sound, where its amplitude rises quickly.
    2. Decay: After the attack, the amplitude begins to decrease.
    3. Sustain: The sound maintains a relatively constant amplitude during this phase.
    4. Release: Finally, the sound fades to silence.

    These stages are critical in music and acoustics for describing the characteristic behavior of sounds, such as a piano note or a vocal sound. The shape of the envelope affects how we perceive the "liveness" or "sharpness" of a sound.

    This page titled 1.8: Sound Envelope was last modified on Fri, 01 May 2026 02:54:53 GMT and is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Geoffrey Dunbar.