Testing microphones in small acoustical enclosures.

Abstract

For both instrument calibration and testing, there is a need for faster and more economical test methods, while keeping the test accuracy within acceptable limits. We analyze the use of a small acoustical enclosure that is not strictly “anechoic” but provides a test environment that can be used to make measurements with a predictably high degree of repeatability for testing the frequency characteristics of the microphones or the influence of their accessories (windscreen and grids). First, the characteristics of the acoustical field in the enclosure are discussed. Then the sensitivity of two test methods to specific influencing parameters is analyzed. The first method is the successive comparison using a reference microphone. The second method is a simultaneous comparison based on the constant divergence of the sound pressure in the field [V. Buzduga and M. Buzduga, “Acoustical test methods based on the constant divergence of the sound pressure level,” Noise Control Eng. J., 51(6), 343–347 (2003)]. The accuracy of the tests and the frequency domain of possible use for each method are discussed.