High-amplitude/low-frequency impulse calibration of microphones; a new method

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Abstract
This paper describes a new method to measure the peak amplitude response and the step‐function decay (low‐frequency response) of a microphone and its associated amplifiers. The requirements for the new method were that it be simple, inexpensive, and accurate. An acoustic ’’step function’’ would be an ideal source for testing the large‐amplitude and low‐frequency response of microphones, especially for measurements of impulsive noise. Unfortunately, a positive going acoustical step‐function source is difficult to obtain. This method involves the use of a negative step‐function input which is applied by enclosing a microphone inside a thin membrane which is inflated and then burst. The sudden decrease in pressure represents a negative going step‐function input to the microphone. The peak output voltage produced by the microphone must be proportional to the initial static pressure within the membrane, and the return (decay) of the voltage output of the the microphone to zero directly represents the decay of the microphone and system. The low‐frequency cutoff of the system is easily calculated from the time constant of the decay curve.

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