Heath Company

Mark Rapaich

A microphone is provided with a read only memory (ROM) which is programmed to compensate for the microphone's nonlinear frequency response characteristic during their integration into a single unit. The ROM is thus programmed to provide a frequency response complementary to that exhibited by the microphone. The microphone may have a relatively poor frequency response over the audio spectrum, i.e., 20 Hz-20 kHz, but with the ROM serving to calibrate the microphone, the combination exhibits a relatively flat frequency response over this frequency range. Intended for use in a portable, battery operated, microprocessor-controlled audio spectrum analyzer, the integrated microphone and ROM combination is coupled to a CMOS random access memory (RAM) in which the calibration contents of the ROM are stored. During normal operation, the microprocessor reads the microphone calibration data from the thus programmed RAM in order to conserve battery power, but may read this data from the ROM when necessary. This permits an inexpensive microphone to be used in a high performance audio spectrum analyzer resulting in a flat frequency response.

ROM compensated microphone

A real-time, microprocessor-controlled, 1/2-octave audio spectrum analyzer is capable of operating in a difference mode wherein a current input may be compared with a previously stored input and the difference therebetween directly displayed in real time. A reference response may be displayed and stored in memory for later comparison with another audio signal for which a spectrum analysis is desired. For example, if an output from a pink noise generator is stored as the reference spectrum and the output from a speaker is the audio signal to be measured, the difference mode of operation will subtract the frequency response of the speaker from that of the noise generator and display the difference. Thus, it is not necessary to take into account frequency response errors of the reference signal source in making highly accurate spectral comparisons.

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Stevensville, MI, United States of America

Mark Rapaich