A time-selective technique for free-field reciprocity calibration of condenser microphones

Salvador Barrera Figueroa, Knud Rasmussen, Finn Jacobsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    796 Downloads (Pure)

    Abstract

    In normal practice, microphones are calibrated in a closed coupler where the sound pressure is uniformly distributed over the diaphragm. Alternatively, microphones can be placed in a free field, although in that case the distribution of sound pressure over the diaphragm will change as a result of the diffraction of the body of the microphone, and thus, its sensitivity will change. In the two cases, a technique based on the reciprocity theorem can be applied for obtaining the absolute sensitivity either under uniform pressure or free-field conditions. In this paper, signal-processing techniques are considered that improve the accuracy of the free-field calibration method. In particular, a fast Fourier transform (FFT)-based time-selective technique for removing undesired reflections from the walls of the measurement chamber has been developed and applied to the electric transfer impedance function between two microphones. The acoustic centers of the microphones have been determined from the "cleaned" transfer impedance values. Then, the complex free-field sensitivities of the microphones have been calculated. The resulting complex sensitivities and acoustic centers have proved to be in good agreement with previously published data, and this confirms the reliability of the time-selective technique, even in nonanechoic environments. Furthermore, the obtained results give a new reference for further comparisons, because they cover a frequency range with an accuracy that has not been obtained by previously published data.
    Original languageEnglish
    JournalAcoustical Society of America. Journal
    Volume114
    Issue number3
    Pages (from-to)1467-1476
    ISSN0001-4966
    DOIs
    Publication statusPublished - 2003

    Bibliographical note

    Copyright (2003) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

    Fingerprint

    Dive into the research topics of 'A time-selective technique for free-field reciprocity calibration of condenser microphones'. Together they form a unique fingerprint.

    Cite this