Latency refers to a short period of delay (usually measured in milliseconds) between when an audio signal enters a system, and when it emerges.
Latency in telephone calls is sometimes referred to as mouth-to-ear delay; the telecommunications industry also uses the term quality of experience (QoE).
The AMR narrowband codec, used in GSM and UMTS networks, introduces latency in the encode and decode processes.
[8] With end-to-end QoS managed and assured rate connections, latency can be reduced to analogue PSTN/POTS levels.
Supported interface optimizations reduce the delay down to times that are too short for the human ear to detect.
Audio lag is also a significant detriment in rhythm games, where precise timing is required to succeed.
In these cases, the notes of a song will be sent to the speakers before the game even receives the required input from the player in order to maintain the illusion of rhythm.
Games that rely upon musical improvisation, such as Rock Band drums or DJ Hero, can still suffer tremendously, as the game cannot predict what the player will hit in these cases, and excessive lag will still create a noticeable delay between hitting notes, and hearing them play.
The person in the main studio has to wait for the contributor at the other end of the link to react to questions.
Wherever practical, it is important to try to keep live production audio latency low in order to keep the reactions and interchange of participants as natural as possible.
Performers, particularly in large spaces, will also hear reverberation, or echo of their music, as the sound that projects from stage bounces off of walls and structures, and returns with latency and distortion.
While analog audio equipment has no appreciable latency, digital audio equipment has latency associated with two general processes: conversion from one format to another, and digital signal processing (DSP) tasks such as equalization, compression and routing.
Any such process takes a small amount of time to accomplish; typical latencies are in the range of 0.2 to 1.5 milliseconds, depending on sampling rate, software design and hardware architecture.
One way for audio engineers to achieve this is to use additional loudspeakers placed at a distance from the stage but closer to the rear of the audience.