Noise in miniature microphones

Stephen C. Thompson, Janice L. LoPresti, Eugene M. Ring, Henry G. Nepomuceno, John J. Beard, William J. Ballad, Elmer V. Carlson

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

The internal noise spectrum in miniature electret microphones of the type used in the manufacture of hearing aids is measured. An analogous circuit model of the microphone is empirically fit to the measured data and used to determine the important sources of noise within the microphone. The dominant noise source is found to depend on the frequency. Below 40 Hz and above 9 kHz, the dominant source is electrical noise from the amplifier circuit needed to buffer the electrical signal from the microphone diaphragm. Between approximately 40 Hz and 1 kHz, the dominant source is thermal noise originating in the acoustic flow resistance of the small hole pierced in the diaphragm to equalize barometric pressure. Between approximately 1 kHz and 9 kHz, the noise originates in the acoustic flow resistances of sound entering the microphone and propagating to the diaphragm. To further reduce the microphone internal noise in the audio band requires attacking these sources. A prototype microphone having reduced acoustical noise is measured and discussed.

Original languageEnglish (US)
Pages (from-to)861-866
Number of pages6
JournalJournal of the Acoustical Society of America
Volume111
Issue number2
DOIs
StatePublished - Feb 16 2002

All Science Journal Classification (ASJC) codes

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

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    Thompson, S. C., LoPresti, J. L., Ring, E. M., Nepomuceno, H. G., Beard, J. J., Ballad, W. J., & Carlson, E. V. (2002). Noise in miniature microphones. Journal of the Acoustical Society of America, 111(2), 861-866. https://doi.org/10.1121/1.1436072