G114
ITU-T Recommendation G.114 specifies and evaluates the delay times and packet losses in packet-switched voice communication.Voice quality can be evaluated subjectively with the MOS value or objectively with the R-factor determined from test procedures.
According to the G.114 rating, voice quality is classified as unacceptable, still acceptable and good.
G.114 is titled "One-way Transmission Time" and specifies how much packet loss and delay is allowed for the G.114 rating. According to this, a packet loss rate of up to 5% is imperceptible and the delay time should be less than 150 ms for acceptable voice quality. If it is greater than 400 ms, the quality is unacceptable.