The ITU-T considers it important that there should be a standardized method of objectively measuring speech level, so that measurements made by different organizations may be directly comparable. Requirements of such a meter are that it should measure active speech level and should be independent of operator interpretation. In this Recommendation, a meter is a complete unit that includes the input circuitry, filter (if necessary), processor and display. The processor includes the algorithm of the detection method. This meter can safely be used for laboratory experiments or can be used with care on operational circuits.
ITU-T P.56-2011 history
2011ITU-T P.56-2011 (Pre-Published) Objective measurement of active speech level
1993ITU-T P.56-1993 Objective Measurement of Active Speech Level - Telephone Transmission Quality Objective Measuring Apparatus (Study Group XII) 15 pp