Subjective quality quantification of digital voice communication systems

The expanding digitisation of the telephone networks has brought about an increasing interest in methods addressing the performance characterisation of new digital voice transmission systems. In the paper a review of subjective methodologies for the assessment of telephone quality digital voice communications systems is provided. Technical aspects concerning the network applications and other characteristics relevant to the type of system under evaluation are considered first, since these factors influence the selection of a suitable assessment methodology. Next, listener opinion and conversational opinion tests are described, with particular emphasis on their respective merits, characteristics and differences. Finally, articulation and diagnostic tests, while not generally employed for the assessment of telephone quality, are briefly examined, since the results obtained from such tests are often correlated with the perceptual performance of telephone quality communications links.