ACOUSTIC BACKGROUND AT THE EARTH'S SURFACE

Abstract

Acoustic background noise at the earth's 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 db/octave 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.

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Document Details

Document Type
Technical Report
Publication Date
Feb 01, 1963
Accession Number
AD0405837

Entities

People

  • John W. Wescott
  • S. S. Kushner

Organizations

  • University of Michigan

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies
  • Weapons Technologies

DTIC Thesaurus Topics

  • Acoustic Propagation
  • Acoustic Waves
  • Acoustics
  • Aircrafts
  • Atmospheric Motion
  • Background Noise
  • Data Processing
  • Detection
  • Dual Channel
  • Engine Noise
  • Engines
  • Flow Noise
  • Frequency
  • High Altitude
  • Laminar Flow
  • Mechanical Jamming
  • Recording Systems

Fields of Study

  • Physics

Readers

  • Acoustics.
  • Computer Science/Computer Engineering/Data Science/Digital Signal Processing.