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.