Constant Pressure dB(A) and dB(C) frequency response of microphones and the expanded uncertainties involved therein

Abstract

In practice, a microphone is calibrated in a closed coupler, wherein sound pressure is distributed uniformly over the diaphragm. Nonetheless, in that case, the problem of sound reflection remains indispensable. A technique that overcomes this limitation and augments the coupler calibration method is offered. Also, the frequency response data provided by the manufacturer is always A-weighted. The A and C-weighted frequency response characteristics of a variety of microphones is studied using the testing and calibration suite, in the direct field of the source, which overcomes the problem of sound reflection. The frequency response in the 100 Hz to 16 kHz frequency range has been examined at constant SPL of 82 dB. The implementation and reliability of the technique is evaluated by examining the expanded uncertainties involved therein. Furthermore, the A-weighted and C-weighted constant pressure frequency response in case of each microphone is compared. A detailed description of the procedure is presented, along with assessments, wherein the reliability of the results is evaluated over Type-A and Type-B uncertainties.