Envelope – ADSR
In music and audio synthesis, the envelope is commonly known as a mechanism to shape the dynamic properties of a sound. The ADSR (Attack, Decay, Sustain, Release) envelope is one of the most prevalent forms of this. Let’s explore each component of the ADSR.
1. Attack
The attack represents the duration it takes for a sound to initiate and attain its peak intensity(the apex of its amplitude). A brief attack time yields a pronounced transient, whereas an extended attack time brings about a sound that rises gently and smoothly.
A swift attack is often observed in percussion and stringed instruments like the piano or guitar. On the other hand, for musical textures or pad sounds that commence slowly, a lengthy attack time might be required.
2. Decay
Decay signifies the time taken after the attack phase for the sound’s intensity to decrease to the sustain level.
A short decay time causes the sound to quickly fall to the sustain value. A lengthy decay time lets the sound diminish gradually. Percussive instruments typically require a short decay duration, while textures or pad sounds might necessitate a longer decay period.
3. Sustain
Sustain indicates the intensity level of the sound maintained after the decay. This value represents the amplitude of the sound (often denoted in dB or %), not its duration. Occasionally, sustain is erroneously labeled as time, so it’s essential not to get confused.
It determines the sound level while continuously pressing a key on a keyboard. A high sustain value ensures the sound remains loud, while a lower value keeps the sound more subdued.
4. Release
Release describes the time it takes for the sound to completely fade away after releasing the key.
A long release time allows the sound to dissipate slowly, giving a reverberation effect. A short release time makes the sound vanish promptly.
It wouldn’t be an exaggeration to say that the ADSR envelope plays one of the most crucial roles in sound. Each phase explicitly details the dynamic characteristics of the sound. In audio processing, if the sound isn’t turning out as desired, it’s a good idea to start by checking the ADSR (dynamic characteristics).