Accession Number:

ADA196566

Title:

System Loss Due to Frequency Limiting of Bottom Bounces

Descriptive Note:

Technical rept.

Corporate Author:

PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB

Personal Author(s):

Report Date:

1988-05-01

Pagination or Media Count:

83.0

Abstract:

Processing systems which incorporate rather narrow frequency acoustic windows are often used for underwater sound measurements. When sound is being received which has bounced off the rough bottom of the ocean, some of the energy being received has returned from points on the bottom which are far from the point of specular reflection between source and receiver. Some Doppler shift is associated with these off-specular reflections when compared with the specular point. In this way, frequency spreading occurs. Thus, some of the acoustic energy returning from the bottom is lost as it is outside the frequency window used by the receiver. It is the goal of this thesis to produce an approximation of this loss, to test the approximation and to understand how the loss level is affected by environmental parameters. A theoretical approximation for the bottom loss integral is derived for the case of a stationary measurement point and an approaching source. Acoustic reflections from the hard, rougher basement are included as well as the energy returned by the overlaying sediment. The final result is compared with the calculations of a computer-based complete model, and conclusions are made concerning the validity of the model.

Subject Categories:

  • Physical and Dynamic Oceanography
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE