Theoretical investigation on the infrasonic frequency response of measurement microphones in different venting states

Abstract

Abstract The demands for metrological traceability of infrasound, and to finally link with the quasi-static pressure metrology require accurate modeling and calibration of measurement microphones. However, two distinct microphone responses were obtained during infrasonic calibrations, when its vent connects to the calibrating sound field or external atmosphere, respectively. But the current theoretical model cannot explicitly characterize this phenomenon. Therefore, this paper focuses on explicitly modeling the infrasonic frequency responses of measurement microphones when its vent connects to the sound field or external atmosphere, respectively. The pressure leakage and heat conduction coupling model of the microphone is first established. Then the second coupling mechanism of the mechanical interaction on microphone diaphragm is studied and the frequency response models of the microphone in two venting states are explicitly derived. The models directly reveal the two coupling mechanisms in primary microphone calibrations. Significant differences of microphone responses between two venting states are verified by calculations.