The amplitude of the minimum audible impulsive sound

I. Introduction.—Investigations of amplitude for continuous sounds produced in a telephone by alternating current have been made by Lord Rayleigh, Franke, Cross and Mansfield. Lord Rayleigh found by an indirect process the value 0·05 µµ for frequency 512, and 0·7 µµ for frequency 256. Other values found by Lord Rayleigh§ are : 0·8 µµ; 1·27 µµ. Toepler and Boltzmann obtained results of the same order. These results cannot be tabulated as the conditions are different, and in some cases unknown. Franke, by more direct measurement, obtained a value 1·2 µµ. The present writer‖ found by direct measurement a value 0·4 µµ in the case of an impulsive sound.