Accession Number:

AD0405837

Title:

ACOUSTIC BACKGROUND AT THE EARTH'S SURFACE

Descriptive Note:

Final rept.

Corporate Author:

MICHIGAN UNIV ANN ARBOR INST OF SCIENCE AND TECHNOLOGY

Personal Author(s):

Report Date:

1963-02-01

Pagination or Media Count:

40.0

Abstract:

Acoustic background noise at the earths surface for frequencies from 0.2 to 100 cps was monitored outdoors with two low-frequency condenser microphones placed 1500 feet apart. The wind speed at each microphone was monitored with cup anemometers. Data were transmitted by microwave links to a central receiving station and recorded on magnetic tape. The acoustic data were preemphasized 6 dboctave before transmission to improve signal-to-noise ratios. Oscillograms of the multichannel acoustic data show cross correlations by visual inspection for the sounds radiated from upper-air turbulence and aircraft. Oscillograms of noise generated locally by surface winds show no apparent cross-correlation. Details of instrumentation are presented. These include a block diagram of the detection, data-link, and recording system and circuit diagrams of components developed for it. A pistonphone calibrator with pushbutton frequencies from 0.125 to 30 cps is described, and its use for amplitude and phase calibration of microphones is explained.

Subject Categories:

  • Acoustic Detection and Detectors
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE