title: Mach-Zehnder interferometry method for acoustic shock wave measurements in air and broadband calibration of microphones.
abstract: A Mach-Zehnder interferometer is used to measure spherically diverging N-waves in homogeneous air. An electrical spark source is used to generate high-amplitude (1800 Pa at 15 cm from the source) and short duration (50 μs) N-waves. Pressure waveforms are reconstructed from optical phase signals using an Abel-type inversion. It is shown that the interferometric method allows one to reach 0.4 μs of time resolution, which is 6 times better than the time resolution of a 1/8-in. condenser microphone (2.5 μs). Numerical modeling is used to validate the waveform reconstruction method. The waveform reconstruction method provides an error of less than 2% with respect to amplitude in the given experimental conditions. Optical measurement is used as a reference to calibrate a 1/8-in. condenser microphone. The frequency response function of the microphone is obtained by comparing the spectra of the waveforms resulting from optical and acoustical measurements. The optically measured pressure waveforms filtered with the microphone frequency response are in good agreement with the microphone output voltage. Therefore, an optical measurement method based on the Mach-Zehnder interferometer is a reliable tool to accurately characterize evolution of weak shock waves in air and to calibrate broadband acoustical microphones.
authors.affiliation: Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Petr
authors.initials: P
authors.lastname: Yuldashev
authors.affiliation: Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Maria
authors.initials: M
authors.lastname: Karzova
authors.affiliation: Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.
authors.forename: Vera
authors.initials: V
authors.lastname: Khokhlova
authors.affiliation: Laboratoire de Mécanique des Fluides et d'Acoustique, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5509, École Centrale de Lyon, Université Lyon 1, 36 Avenue Guy de Collongue, 69131 Écully Cedex, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Ollivier
authors.affiliation: Laboratoire de Mécanique des Fluides et d'Acoustique, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5509, École Centrale de Lyon, Université Lyon, 36 Avenue Guy de Collongue, 69131 Écully Cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Blanc-Benon