Technical Note: Acoustical test method based on the constant divergence of the sound pressure level

This paper presents new test methods that use the difference between the sound pressure levels at two locations in the field of a sound source for determining the acoustical parameters of the transducers or attached attenuating devices. First the sound pressure field is discussed and it is concluded that its constant divergence with regard to power level of the sound source may be used for accurate acoustical measurements. Test methods based on this approach for measuring the insertion loss of windscreens and frequency response characteristics of microphones are then described. Finally experimental results and proposals for further developments are presented.