Research Papers

An Improved Technique for Measuring the Vibration Sensitivity of Subminiature Microphones

[+] Author and Article Information
Jonathan D. Walsh

Department of Mechanical Engineering,
Binghamton University,
Binghamton, NY 13902
e-mail: jwalsh3@binghamton.edu

Quang T. Su

Department of Mechanical Engineering,
Binghamton University,
Binghamton, NY 13902
e-mail: qsu@binghamton.edu

Daniel Warren

GN Advanced Science,
Glenview, IL 60026
e-mail: dwarren@gnresound.com

Contributed by the Noise Control and Acoustics Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received August 10, 2017; final manuscript received December 3, 2017; published online January 25, 2018. Assoc. Editor: Theodore Farabee.

J. Vib. Acoust 140(3), 031008 (Jan 25, 2018) (7 pages) Paper No: VIB-17-1363; doi: 10.1115/1.4038681 History: Received August 10, 2017; Revised December 03, 2017

Presented is a test methodology for characterizing the vibration sensitivity of miniature microphones. An ordinary vibration sensitivity experiment becomes difficult because vibrating surfaces are also sources of sound. This sound is picked up by the microphone being tested, changing the result. The sound pressure will be correlated with the vibration signal such that averaging will not serve to increase the accuracy of that result.The previously described techniques reduce the correlated pressure using custom experimental equipment and have geometric limitations. In the improved technique, the microphone is treated like a linear two-input-one-output system. The two input signals (vibration and acoustic pressure) are measured, and the vibration sensitivity is determined using two different spectral analysis techniques. These techniques have good agreement between one another, and the measured values fit well into a simple acoustic model of the microphone. A technique for estimating the major source of measurement error indicates that this error is small enough for a reasonable estimate of vibration sensitivity to be made.

Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.


Rule, E. , Suellentrop, F. J. , and Perls, T. A. , 1960, “ Vibration Sensitivity of Condenser Microphones,” J. Acoust. Soc. Am., 32(7), pp. 821–823. [CrossRef]
Friis, L. , 2009, “ Investigation of Internal Feedback in Hearing Aids,” Ph.D. thesis, Technical University of Denmark, Lyngby, Denmark. http://orbit.dtu.dk/en/publications/investigation-of-internal-feedback-in-hearing-aids(3c5ffce2-9828-4a4f-93ba-51e7eb0508ff).html
Killion, M. C. , 1974, “ Vibration Sensitivity Measurements on Subminiature Condenser Microphones,” 49th Convention of the Audio Engineering Society, New York, Sept. 9–12. https://www.etymotic.com/media/publications/erl-0057-1975.pdf
Koukias, S. , 2011, “ Vibration Sensitivity of Miniature Microphones,” Master's thesis, Technical University of Denmark, Lyngby, Denmark.
Bendat, J. S. , and Piersol, A. G. , 2011, Random Data: Analysis and Measurement Procedures, 4th ed., John Wiley & Sons, New York.
Bendat, J. S. , and Piersol, A. G. , 1980, Engineering Applications of Correlation and Spectral Analysis, John Wiley & Sons, New York.


Grahic Jump Location
Fig. 5

A speaker-driven measurement. The microphone does not vibrate and therefore the acoustic sensitivity is measured.

Grahic Jump Location
Fig. 4

The vibration measurement. The microphone behaves like a two-input-one-output system.

Grahic Jump Location
Fig. 3

A microphone's signal is a combination of an acoustic response and the vibration response

Grahic Jump Location
Fig. 2

Experimental setup diagram

Grahic Jump Location
Fig. 1

The experimental setup includes a shaker, speaker, probe microphone, and accelerometer/vibrometer

Grahic Jump Location
Fig. 6

Simultaneous uncorrelated speaker and shaker signals combine. This meets the requirement, γvp2≠0, in Eq. (8).

Grahic Jump Location
Fig. 7

Diagram of the sound pressure verification test. The microphone's motion is fixed near a vibrating shaker surface.

Grahic Jump Location
Fig. 8

The sound pressure verification test. The microphone is held in place on a clamped metal surface near to the shaker.

Grahic Jump Location
Fig. 9

Analytical model of a microphone. The diaphragm mass m at l = 0 separates the back-volume from the front-volume. Sound pressure enters the device at l = Lf.

Grahic Jump Location
Fig. 11

The two techniques for estimating vibration sensitivity and the decibel difference between them

Grahic Jump Location
Fig. 12

The cavity technique in Killion [4] (using data from Friis [3]), compared to the technique in Sec. 2.2. Both curves are from similar electret microphone devices.

Grahic Jump Location
Fig. 10

The vibration caused by the speaker is similar to the experimental background noise

Grahic Jump Location
Fig. 13

Coherence for the techniques of Secs. 2.2 (Technique 1) and 2.3 (Technique 2)

Grahic Jump Location
Fig. 14

The vibration sensitivity estimate compared with the estimated error caused by sound pressure measurement

Grahic Jump Location
Fig. 15

The difference between the (dBSPL) vibration sensitivity estimate and the estimated error due to sound pressure measurement

Grahic Jump Location
Fig. 16

The pressure sensitivity of a more massive (thicker) diaphragm decreases at low frequencies and increases at high frequencies

Grahic Jump Location
Fig. 17

The vibration sensitivity of a more massive (thicker) diaphragm increases at all frequencies

Grahic Jump Location
Fig. 18

The input referred vibration sensitivity of the experimental measurement is predicted by the analytical model for diaphragm thickness hd = 1 μm. A thinner or less massive diaphragm tends to decrease the (Pa/g) vibration sensitivity.




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In