Accession Number : AD0730909

Title :   Pressure Reciprocity Calibration of Condenser Microphones in 100 Percent Helium at Various Atmospheric Pressures,

Corporate Author : DAYTON UNIV OHIO RESEARCH INST

Personal Author(s) : Kettler,L. Keith

Report Date : JUL 1971

Pagination or Media Count : 28

Abstract : Four condenser type microphones (W. E. Type 640AA and B and K Type 4131) were calibrated in a 100% helium atmosphere using the pressure reciprocity calibration method. This calibration was performed at three different atmospheric pressures, ranging from 739 mm Hg to 257.5 mm Hg. This test was in support of a research study of the effects of helium on the ability to generate speech. Findings of the study indicate that the sensitivities of the microphones were only slightly reduced in helium compared to air. An average decrease in sensitivities of 0.5 dB or less was observed over the test frequency range of 100 to 4000 Hz when compared with the associated normal air sensitivities. (Author)

Descriptors :   (*MICROPHONES, CALIBRATION), CONFINED ENVIRONMENTS, HELIUM, OXYGEN, TEST METHODS

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE