Record Display for the EPA National Library Catalog


Main Title Environmental Effects on Microphones of Various Constructions.
Author Hruska, Gale R. ; Magrab, Edward B. ; Penzes., William B. ;
CORP Author National Bureau of Standards, Washington, D.C.;Environmental Protection Agency, Washington, D.C. Office of Noise Abatement and Control.
Year Published 1977
Report Number NBS-2003110;
Stock Number PB-263 258
Additional Subjects Microphones ; Sensitivity ; Calibrating ; Pressure ; Capacitors ; Ceramics ; Electrets ; Temperature ; Humidity ; Environmental tests ; Reprints
Library Call Number Additional Info Location Last
NTIS  PB-263 258 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 5p
The pressure sensitivities of two 1/2-in. electret, two 1-in. ceramic, and two backvented 1-in. condenser microphones were measured for numerous combinations of temperature, percentage relative humidity, and frequency. The two condenser microphones were calibrated by the reciprocity technique at each combination of temperature, relative humidity, and frequency. The condenser microphones were then used as calibrated sources to determine the pressure sensitivities of the other microphones. Insert voltage techniques were used to eliminate the environmental effects on the electronics. It was found that the back-vented condenser microphones are insensitive to changes in relative humidity. At frequencies considerably below their resonance frequencies they exhibited only a very small change in sensitivity with temperature. At frequencies closer to the resonance frequency the temperature coefficient increases approximately fourfold. The temperature and humidity coefficient for the electret and ceramic microphones could not be determined due to the instability in their sensitivities which produced changes that were larger than those induced by the temperature and humidities.