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Proceedings Paper

Mechanical-thermal noise characterization of a new micromachined acoustic sensor
Author(s): B. Mezghani; F. Tounsi; M. Masmoudi
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Paper Abstract

A new integrated CMOS micromachined inductive microphone is studied and characterized for mechanical-thermal noise. This acoustic sensor has one suspended membrane attached to the substrate with 4 arms, the I-beam or L-beam shaped attachments. This membrane has 1.4x1.4mm2 active area, 22&mgr;g mass and its natural frequency is found to be around 250 kHz, for the I-beam and 134 kHz, for the L-beam attachment. We give a brief explanation of the superiority of this new design over conventional acoustic sensors. Then, some experimental points are discussed and solutions are given. This sensor is analyzed for mechanical-thermal noise by applying a new developed analysis based on mass and natural frequency. Our system damping factor is found to be 5x10-2 N.s.m-1, which gives a fluctuating force spectral density of 2.88x10-11 N.Hz-1/2. This corresponds to an A-weighted sound level of about 39 dB(A) SPL. A SNR value of 55 dB is found for an incident pressure of 1 Pa on the suspended membrane. The relationship between the SNR and the mechanical and geometrical characteristics of the suspended membrane is also investigated. Finally, our sensor mechanical noise displacement is evaluated, around 10-15 m.Hz-1/2, and plotted for the two attachment types.

Paper Details

Date Published: 11 June 2007
PDF: 9 pages
Proc. SPIE 6600, Noise and Fluctuations in Circuits, Devices, and Materials, 660015 (11 June 2007); doi: 10.1117/12.720185
Show Author Affiliations
B. Mezghani, National Engineering School of Sfax (Tunisia)
F. Tounsi, National Engineering School of Sfax (Tunisia)
M. Masmoudi, National Engineering School of Sfax (Tunisia)

Published in SPIE Proceedings Vol. 6600:
Noise and Fluctuations in Circuits, Devices, and Materials
Massimo Macucci; Lode K.J. Vandamme; Carmine Ciofi; Michael B. Weissman, Editor(s)

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