A New Standard Volume Indicator and Reference Level

H E s t u d e n t of electrical engineering, when i n t r o d u c e d to alternating current theory, learns t h a t there are three related values of a sine w a v e by which its m a g n i t u d e m a y be expressed. These are t h e a v e r a g e v a l u e , t h e r - m - s (or e f f e c t i v e ) v a l u e , a n d t h e p e a k (or c r e s t ) value. Certain f u n d a m e n t a l electrical m e a s u r i n g devices provide m e a n s for determining these values. As the student's experience broadens, he becomes familiar with complex, non-sinusoidal periodic waves and finds t h a t these waves have the same three readily measured values. He learns how to determine from the problem under consideration whether the average, the r-m-s or the peak value of the wave is of p r i m a r y i m p o r t a n c e . * Presented at joint meeting of A. I. E. E. and I. R. E., San Francisco, California, June 1939, and at Fourteenth Annual Convention of I. R. E., New York, September 1939. t Mr. Howard A. Chinn is Engineer-in-Charge, Audio Engineering, Columbia Broadcasting System, Inc. { Mr. Robert M. Morris is Development Engineer, National Broadcasting Company, Inc. 94