How to Build a Microphone
Microphones are transducers for converting acoustic pressure fluctuations into analogous electrical output signals. Various types of microphones are available, each optimised to meet particular requirements regarding performance, price, reliability and stability. Measurement microphones are optimised for performance, stability and reliability, but are influenced by the same design parameters as are other types of microphones. For measurement purposes, the condenser microphone has proved to be the best choice. It combines accuracy with stability and can be constructed to meet the requirements for measuring sound in free-fields, diffuse fields and in the couplers of equipment for testing and adjusting hearing aids. The design parameters include such factors as size, diaphragm stiffness, internal damping and diaphragm mass. By varying these design parameters, measurement microphones can be designed to have the desired combination of frequency response characteristics and dynamic range. The important design characteristics to consider are sensitivity, dynamic range and directionality. These are looked at in some detail. In the case of a 1/2“ condenser microphone (a) limiting the frequency response to lie within 20 kHz to 40 kHz, (b) limiting diaphragm deflection to about 1/10 of the distance between itself and the back plate and (c) correctly adjusting the acoustic damping behind the diaphragm, will produce the best results.
KeywordsSound Pressure Sound Pressure Level Sound Field Frequency Response Characteristic Diaphragm Mass
Unable to display preview. Download preview PDF.