scope:

This Recommendation describes a subjective test methodology which is able to assess and diagnose the quality of speech in a "telephone conversation" scenario. Common conversation tests, as described in [ITU-T P.800] and [ITU-T P.805], provide valid methods for the overall conversational quality, but do not give insights into reasons for possible quality losses. In addition, common conversational tests lack analytic ability, since naïve participants concentrate on the conversation flow. To circumvent these problems, this Recommendation describes a test methodology that specifically allows participants to perceive each phase of a conversation separately, in addition to a natural conversation, and yields overall conversational quality scores as well as quality scores for each phase (listening, speaking, interaction). In addition, scores for seven underlying perceptual dimensions of conversational speech quality are provided. These scores enable the analysis of conversational speech quality for diagnosis and optimization.