Interference Versus Frequency in Measurements in a Shallow Lake

Abstract

When an omnidirectional projector and hydrophone are closely spaced and in shallow water, and sound is transmitted from one to the other, a large interference signal is superimposed on the direct signal. If the received signal is plotted as a function of frequency, as in a calibration measurement, the interference signal amplitude appears to be an inconsistent series of irregular sharp peaks and dips. A mathematical analysis of the condition where the transducers are midway between a water-air surface and a bubble-covered bottom shows that the shape, amplitude, and frequency of the interference pattern are predictable as the result of a large number of multireflection paths.

Open PDF

Document Details

Document Type
Technical Report
Publication Date
Nov 15, 1961
Accession Number
ADA044708

Entities

People

  • Robert J. Bobber

Tags

DTIC Thesaurus Topics

  • Acoustic Waves
  • Acoustics
  • Amplitude
  • Boundaries
  • Fourier Series
  • Frequency
  • Frequency Response
  • Hydrophones
  • Intermediate Frequencies
  • Lepidoptera
  • Long Wavelengths
  • Mathematical Analysis
  • Measurement
  • Reflection
  • Transducers
  • Underwater Sound
  • Waves

Readers

  • Acoustical Oceanography.
  • Plasma Physics / Magnetohydrodynamics

Technology Areas

  • Space