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Radio device detects airplane sound twenty miles off
Washington June 29 A new radio amplifying device from the U S Bureau of Standards can detect the sound of an airplane up to 20 miles away and locate its direction within eight to ten miles. The instrument uses a large horn perforated brass plate aluminum diaphragm and a high gain resistance coupled amplifier. Dr August Fund credits the horn plate and diaphragm design as the key enabling audio detection and direction finding.
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Washington
U. S. Bureau of Standards
August Fund
Bureau of Standards