The Determination of the Acoustical Output of a Telephone Receiver from Input Measurements
Richard D. Fay, William M. Hall · The Journal of the Acoustical Society of America · 1933
The paper describes how an analysis of the functioning of a telephone receiver can be made by measuring the terminal electrical impedance of the receiver as a function of the length of a closed tube into which it works. With these data it is possible to calculate the excess pressure and the velocity of the air at the mouth of the receiver in relation to the voltage across the input terminals for any load condition. The analysis therefore furnishes means both for measuring acoustic impedance and for producing sound of known intensity.