A New Standard Volume Indicator and Reference Level

In recent years it has become increasingly difficult to correlate readings of volume level made by various groups because of differences in the characteristics and calibrations of the volume indicators used. This paper describes a joint development by the Columbia Broadcasting System, National Broadcasting Company, and Bell Telephone Laboratories which resulted in agreement upon, and standardization in the respective broadcast and telephone plants of a new copper-oxide-rectifier type of volume indicator having prescribed dynamic and electric characteristics; a new reference level based on the calibration of the new instrument with a single-frequency power of 1 milliwatt; and a new terminology, the readings being described in "vu." It is hoped that other users of volume indicators will join in the adoption of these new standards. The paper gives in considerable detail the technical data and considerations on which was based the choice of the characteristics of the new volume indicator and the other features of the new standards. Particular attention is paid to the technical data supporting the decision to make the new volume indicator approximately a root-meansquare rather than a peak-reading type of instrument.