The increasing variety of speech transmission systems has created a new problem for communication engineers. This problem consists of the subjective evaluation of the speech quality produced by these systems. For investigators interested only in the utilization of some procedure applicable to this problem, it was difficult to make a choice among the wide range of documented approaches. The IEEE Audio and Electroacoustics Group therefore formed a Subcommittee on Subjective Measurements, which has been charged with writing a Recommended Practice for speech quality measurement. The intent of the Subcommittee became to write a document that would facilitate the choice of method by reducing the variety of procedures to several which had been successful and looked promising for the future, and which could handle a variety of signals. By describing these methods in some detail, it would be possible for different laboratories to obtain comparable results and thus aid in the exchange of informa...

Speech quality is based on the subjective appraisal of speech. Speech may be appraised on the basis of preference, loudness, intelligibility, and recognizability of properties of the original speaker's voice, of the transmission channel, and/or in the case of artificial speech, of the speech synthesizer. The IEEE Subcommittee on Subjective Measurements, charged with writing an engineering practice for the measurement of speech quality, has concluded that a single method should not now be recommended. The present Recommended Practice is concerned only with preference measurements for which three methods will be tentatively outlined. These are the Isopreference Method, the Relative Preference Method, and the Category-Judgment Method.