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Measurement Of The Diffraction Correction Of The Gulton Model P420m-6 Microphone

Report Number: AFFDL TR 66-223
Author: Ortega, Jose C.
Corporate Author: Western Electro-Acoustic Lab Inc Santa Monica CA
Laboratory: Flight Dynamics Laboratory
Date of Publication: 1967-05
Pages: 42
Contract: AF 33(615)-3746
Project: 1472
Task: 147203
AD Number: AD0816179

The methods and instrumentation used to obtain the diffraction correction for the Gulton P420M-6 microphone are described. The diffraction correction was measured for two microphone mounting configurations at several angles of sound incidence over the frequency range 400 cps to 25K cps. In addition, the random incidence response for the Gulton P420M-6 microphone was obtained over the same frequency range. Analysis of the measured data shows that the precision of the measurements is very good below 15K cps (standard deviation being within plus or minus .6 db) and gradually decreases at higher frequencies (standard deviation being plus or minus 1.2 db at 20K cps and +3.9 db, -7.4 db at 25K cps). The pressure calibration for the Gulton P420M-6 microphone was obtained using the well known coupler method and also using an electrostatic actuator. The results of these measurements show that the electrostatic actuator method of calibration produces reliable results when used with the Gulton microphone.

Lockheed Martin Missiles & Fire Control
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