Mach-Zehnder interferometry method for acoustic shock wave measurements in air and broadband calibration of microphones

摘要: A Mach-Zehnder interferometer is used to measure spherically diverging N-waves in homogeneous air. An electrical spark source generate high-amplitude (1800 Pa at 15 cm from the source) and short duration (50 μs) N-waves. Pressure waveforms are reconstructed optical phase signals using an Abel-type inversion. It shown that interferometric method allows one reach 0.4 μs of time resolution, which 6 times better than resolution a 1/8-in. condenser microphone (2.5 μs). Numerical modeling validate waveform reconstruction method. The provides error less 2% with respect amplitude given experimental conditions. Optical measurement as reference calibrate microphone. frequency response function obtained by comparing spectra resulting acoustical measurements. optically measured pressure filtered good agreement output voltage. Therefore, based on reliable tool accurately characterize evolution weak shock waves air broadband microphones.