Development of a Laser Pistonphone System to Calibrate the Sensitivity Modulus and Phase of Microphones for Infrasonic F
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International Journal of Precision Engineering and Manufacturing https://doi.org/10.1007/s12541-020-00338-4
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Development of a Laser Pistonphone System to Calibrate the Sensitivity Modulus and Phase of Microphones for Infrasonic Frequencies Jae‑Gap Suh1 · Wan‑Ho Cho1 · Triantafillos Koukoulas2 · Hack‑Yoon Kim3 · Zhenglie Cui4 · Yôiti Suzuki5 Received: 20 October 2019 / Revised: 10 March 2020 / Accepted: 19 March 2020 © Korean Society for Precision Engineering 2020
Abstract A laser pistonphone system capable of measuring the sensitivity modulus and phase of microphones is proposed. For the primary vibration calibration, the sine-approximation method has been applied which is used to calculate the complex sensitivity of accelerometers. This method is based on a laser interferometer with quadrature output instead of the fringe-counting method that is used in conventional laser pistonphones. Here, the laser pistonphone system based on the sine-approximation method with the quadrature signal is proposed and the measured results are compared to those obtained by the reciprocity method. The measured sensitivity with the proposed method agrees well with the result of the reciprocity method for the infrasound range. However, in case of the phase sensitivity, the discrepancy is relatively high in comparison to the sensitivity modulus. The results show that the proposed system is capable of calibrating the complex sensitivity of microphones. The improvement of the uncertainty and extension of the frequency range can be achieved by modification of the excitation system for obtaining the required stable excitation with long stroke. Keywords Infrasound · Infrasound calibration · Phase calibration · Laser pistonphone
1 Introduction Infrasonic detection and monitoring, is an important technical area with different applications including prediction of natural disasters related to earthquakes, volcanoes and tsunamis, to monitoring of man-made noise associated with wind turbine for instance. * Wan‑Ho Cho [email protected] 1
Division of Physical Metrology, Korea Research Institute of Standards and Science, 267 Gajeong‑ro, Yuseong‑gu, Daejeon 34113, Korea
2
National Research Council Canada, Cheongju University, 1200 Montreak Riadm BLDG N36, Ottawa, Ontatio K1A 0R6, Canada
3
Department of Electronic Engineering, Cheongju University, 298 Daesung‑ro, Cheongju 28503, Korea
4
Aichi University of Technology, Manori‑50‑2 Nishihasamacho, Gamagori, Aichi 443‑0047, Japan
5
National Institute of Information and Communications Technology, 2‑1‑3, Katahira, Aoba, Sendai‑city, Miyagi 980‑0812, Japan
Currently, the unit of sound-in-air measurement, the acoustic decibel (dB) is indirectly defined by using the sensitivity of laboratory standard (LS) microphone and the international standard of sound measurement is based on the reciprocity method [1] to calibrate LS microphones [2]. The reciprocity method is an absolute calibration method capable of yielding the sensitivity of LS microphones with uncertainties low
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