Accession Number : ADA116105

Title :   Frequency Dispersion of Sound in Undersea Propagation.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : Gerlach,A A ; Flowers,K D ; Johnson,R B , Jr ; Anderson,W L ; Kunz,E L

PDF Url : ADA116105

Report Date : 17 Jun 1982

Pagination or Media Count : 53

Abstract : Acoustic dispersion in a deep ocean channel is characterized by the dependence of sound propagation speed on signal frequency along the axial propagation path. A model normal-mode solution of the wave equation is employed to compute the acoustic field for sinusoidal signals as a function of both axial range and frequency. A virtual propagation time is defined, which reflects the range-dependent phase of the acoustic field. When signals of different frequency are transmitted, the remotely observed frequency ratio (for a given range-rate) will fluctuate about the true frequency ratio of the transmitted signals. The magnitude of the fluctuation is directly proportional to the true frequency ratio. A measure of the spectral dispersion is defined as the difference between the observed and true frequency ratios. The dependence of this measure on range and signal frequencies (for a given frequency ratio) is determined to be relatively insignificant. It is concluded that spectral acoustic dispersion in a deep ocean channel is microscopic, but it can be significant for applications involving the phase correlation of broadband (or spectrally separated) signals over long time intervals. (Author)

Descriptors :   *Underwater sound signals, *Wave propagation, Acoustic fields, Dispersions, Deep oceans, Broadband, Wave equations, Sound transmission

Subject Categories : Acoustics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE