Date of Award

Fall 1990

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Griffith J. McRee

Committee Member

Allen J. Zuckerwar

Committee Member

Linda L. Vahala

Call Number for Print

Special Collections LD4331.E55N56

Abstract

The electrical noise generated by thermal agitation of the air molecules impinging upon the membrane of a condenser microphone and from its associated preamplifier has been studied analytically and experimentally over a wide bandwidth. These background noise levels constitute one of the most important specifications of a microphone for they determine the lowest sound pressure that can be detected. Therefore, a new method for measuring the thermal agitation noise within a bandwidth of 1-25600 Hz has been developed. The theoretical and experimental measurements of thermal agitation noise in a condenser microphone by enclosing the microphone in a vessel which is isolated from the environment, acoustically by means of a high vacuum and vibrationally by means of an effective suspension system, will be discussed. For the first time it has been found experimentally that there is a 1/f noise source in the membrane of the microphone. Measurements of sound propagation into the isolation vessel as a function of vacuum at different frequencies are compared to theory.

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DOI

10.25777/k6pq-mq39

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