G.114 is an ITU recommendation that addresses acceptable delays for voice applications, is oriented to national telecommunications and is more stringent than what is normally applied in private voice networks.

One of the things it addresses is voice delay. It says < 150 milliseconds is acceptable, > 400 milliseconds is unacceptable and in between people should be made aware of quality issues.

References

• ITU-T Recommendation G.114 - (Recommendation G.114 (05/03))