B Milhomem Thiago Antônio, Defilippo Soares Zemar M, Musafir Ricardo E, Müller Swen
Laboratory of Electroacoustics, Acoustics and Vibration Metrology Division, Scientific and Technology Metrology, National Institute of Metrology, Quality and Technology, Avenida Nossa Senhora das Graças, 50, Prédio 1, Xerém, Duque de Caxias, Rio de Janeiro, 25.250-020, Brazil.
Department of Mechanical Engineering, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, 21.941-972-68.503, Brazil.
J Acoust Soc Am. 2017 May;141(5):3132. doi: 10.1121/1.4983005.
This paper presents a procedure for free-field calibration of half-inch laboratory standard microphones by reciprocity that allows the identification and removal of the electrical cross-talk, multiple backscattering, reflections, noise, and all harmonic distortion components when measuring the electrical transfer impedance between the microphones. Initially, the difficulties of free-field calibration of condenser microphones by the reciprocity method are pointed out and the state of art is summarized. Following, the proposed procedure, which allows determining microphone sensitivities in the frequency range from 1 kHz to 40 kHz, is described: The cross-talk is removed by subtraction while multiple backscattering, reflections, noise and all harmonic distortion components are removed by a time-selective technique. Measurements and results are presented and discussed. A comparison between the results obtained by the proposed procedure and the pressure field calibration results corrected to free-field shows the efficiency and accuracy of the technique.
本文介绍了一种通过互易法对半英寸实验室标准传声器进行自由场校准的程序，该程序能够在测量传声器之间的电传输阻抗时识别并消除电串扰、多次反向散射、反射、噪声以及所有谐波失真分量。首先，指出了采用互易法对电容传声器进行自由场校准的困难，并总结了当前的技术水平。接下来，描述了所提出的程序，该程序能够确定1kHz至40kHz频率范围内传声器的灵敏度：通过减法消除串扰，同时通过时间选择技术消除多次反向散射、反射、噪声以及所有谐波失真分量。给出并讨论了测量结果。将所提出的程序获得的结果与校正为自由场的压力场校准结果进行比较，显示了该技术的效率和准确性。
