Identifying Speech Quality Dimensions in a Telephone Conversation

Speech telecommunication services are traditionally used for communication between two interlocutors interacting in a conversation. Thus, the quality of transmitted speech in a conversational situation, as perceived by the end-users, is the important indicator for service providers to evaluate their systems. In this context, it is not enough to only provide information about the overall quality but also to indicate reasons and sources for quality losses. In this article, we present an approach towards analyzing speech quality in a conversational situation by dividing a conversation into three separate phases and identifying corresponding quality-relevant perceptual dimensions, as perceived by the system users. The identified dimensions can be combined for the overall quality assessment and may separately be used to diagnose the technical reasons of quality degradations. For this, four separate subjective experiments to uncover the underlying dimensions in each conversational phase are conducted. The resulting quality-profile, consisting of seven perceptual dimensions, is then validated in an extensive conversational experiment triggering all three phases of a conversation using a new proposed test-paradigm. This allows deeply analyzing conversational speech quality for diagnosis and optimization of telecommunication systems and provides the fundamentals for instrumental diagnostic conversational speech quality measures.