Sustain
The term sustain ( English for maintaining, stamina ) referred to in the acoustics certain aspects of the sound behavior of sound generators. The term has two different meanings, depending on whether it is acoustically or electronically generated sounds.
Sustain with acoustic sound generators
With acoustic sound generators, especially with musical instruments , sustain describes the length of the decay of a note after it has been triggered manually or automatically.
If the physical decay of the sound-producing parts of instruments (for example strings ) quickly after triggering and consequently the volume of the sound produced decreases quickly, the sound generator has a short sustain; If this decay and thus the generated tone persists for a long time without having to operate the tone generator again, this is called long sustain.
While the sustain on percussion instruments is extremely short due to the rapid fading of the sound, the sustain on mechanical instruments (such as the organ ) can theoretically be infinitely long. On the piano , sustain can be influenced by the right pedal , which controls the damper on the strings .
The term sustain is not to be confused with the reverberation (Engl. Reverberation ), as is made when the sustain sustaining signal from the instrument itself. With reverberation , a reflection of the sound propagation in the air takes place or is generated in electronic reverberation devices, which behaves independently of the natural sound duration of an instrument.
Sustain in electronic sound generators
In the case of electronically generated sound signals such as analog or digital synthesizers or samplers, the term sustain denotes a phase of the tone's envelope. Sustain is the third of four idealized phases ( ADSR ) in the envelope of the tone volume and here does not denote a duration, but the volume level of the tone in the quasi-stationary state.