The delay is the time interval between a sound and a repeat of that sound, used to create an echo effect.

 

Delay effects are a family of electronic effects that alter a sound by adding a duplicate signal that is delayed in relation to the original signal.

 

Extremely small delays are heard as timbral modification: delay on the order of 3 to 16 milliseconds (ms) creates a flange effect; delay of 20 to 40 milliseconds (with pitch modulation) creates a chorus effect.

 

Longer delays are more characteristic of reflected sound, and thus are heard as reverberation or echo: delay on the order of 30 ms (without pitch modulation) is heard as reverb; delay of about 50 to 80 milliseconds creates bathtub reverb; delay of about 90 to 140 milliseconds creates a slapback echo; and delays on the order of hundreds of milliseconds are heard as echo within proportionally larger spaces.