Speech Volumes on Bell System Message Circuits -- 1960 Survey

T h e volume of message signals at various points in the telephone network is of importance to those who design and engineer telephone systems and equipment, and ultimately, of course, to the listener at the far end of the connection. This volume is influenced not only by the speech pressure produced by the talker and by his habits in using the telephone set, but also by the characteristics of the set, the battery supply and loop resistance, and the electrical loss (or gain) between the set and the point at which knowledge of the level is desired. Speech signals are very complex quantities varying in amplitude from instant to instant. They are measured in a prescribed manner on a standardized meter known as a volume indicator. D a t a obtained using this technique are called speech volumes and are expressed as volume units (VU) on a db scale. Such measurements are of value to engineers who design equipment, determine crosstalk objectives and permissible noise levels, and otherwise engineer the telephone network. Since changes in the telephone plant affect transmission performance of the lines, and consequently may affect the customers' habits in the use of the telephone set, up-to-date information on customer speech volumes is necessary. When the last general survey of speech volumes on Bell System message circuits was made in 1950-1951, 1 a large percentage 1999