Some acoustic experiments with telephone receivers

A Rayleigh disc is used to find the resonant frequency and decay factor of a telephone receiver under different circumstances as regards diaphragm clamping and air cavity behind the diaphragm. The field of sound in front of a resonator tube and a telephone receiver is investigated by the Rayleigh disc and by a device for measuring sound pressures, and direct measurements are made of the overall acousticai-electrical efficiency of a telephone receiver.