This Recommendation gives the algorithm for the so-called E-model as the common ITU-T Transmission Rating Model. This computational model can be useful to transmission planners, to help ensure that users will be satisfied with end-to-end transmission performance. The primary output of the model is a scalar rating of transmission quality. A major feature of this model is the use of transmission impairment factors that reflect the effects of modern signal processing devices.

In the year 2000 revision, an enhanced version of the E-model was provided, in order to better take into account the effects of room noise at the send side, and quantizing distortion. With the year 2002 revision, the impairment due to random packet-loss has been included in a parametric way for different codecs. The current version (2003) provides an enhanced modelling of the quality in case of low talker sidetone levels.