Cavity coupler

To determine the pressure sensitivity of a microphone, a rigid cavity is used to couple the sound source to the microphone. This method is useful for determining a microphone's pressure sensitivity by comparison with the sensitivity of a calibrated reference microphone. To obtain sufficiently uniform sound pressure inside the cavity, this method shall only be used within the limits of the frequency range where the linear dimensions of the cavity are less than one-tenth of the wavelength. At low frequencies, care shall be taken to eliminate air leakage. (Ref. IEC 60268-4).