# Accession Number:

## ADA159848

# Title:

## An Inverse Method for Obtaining the Attenuation Profile and Small Variations in the Sound Speed and Density Profiles of the Ocean Bottom.

# Descriptive Note:

## Doctoral thesis,

# Corporate Author:

## WOODS HOLE OCEANOGRAPHIC INSTITUTION MA

# Personal Author(s):

# Report Date:

## 1985-05-01

# Pagination or Media Count:

## 248.0

# Abstract:

The acoustic properties of marine sediments have a direct effect on the propagation of sound in the ocean. In the frequency range of interest 50 - 500 Hz the sediment can be modelled as a fluid. Assuming horizontal stratification of the ocean bottom, the acoustical parameters of interests are the compressional wave speed, the compressional wave attenuation and density as a function of depth. This thesis presents an inverse method, based on a perturbation technique, determining these parameters. A monochromatic source experiment is proposed because of the desirability of such an experiment for determining the acoustic properties of an anelastic medium. The input information is the plane wave reflection coefficient as a function of the angle of incidence at a fixed frequency. A nonlinear integral equation relating the variations of these acoustic properties from a known reference value to the plane wave reflection coefficient is derived and is then linearised using the Born approximation. The region of validity of the Born approximation is derived and, based on this, the optimum angular aperture for the input data is obtained. The linearised integral equation is a Fredholm integral equation of the first kind. An acceptable stable solution of the integration is obtained with noise free data show good agreement between the true profiles and the reconstructed profiles.

# Descriptors:

- *ACOUSTIC ATTENUATION
- *SEDIMENTS
- COMPRESSION
- VELOCITY
- MATHEMATICAL MODELS
- FREQUENCY
- DATA PROCESSING
- INPUT
- FUNCTIONS
- DENSITY
- STABILITY
- ELASTIC PROPERTIES
- THESES
- REFLECTION
- DEPTH
- VARIATIONS
- SOLUTIONS(GENERAL)
- PROFILES
- COEFFICIENTS
- SOUND TRANSMISSION
- ATTENUATION
- PERTURBATIONS
- INVERSION
- HORIZONTAL ORIENTATION
- NOISE
- RANGE(EXTREMES)
- INTEGRAL EQUATIONS
- ANGLE OF INCIDENCE
- UNDERWATER ACOUSTICS
- ACOUSTIC VELOCITY
- STRATIFICATION
- ACOUSTIC DATA
- PLANE WAVES
- OCEAN BOTTOM
- WAVES
- ACOUSTIC PROPERTIES
- ELASTIC WAVES
- ACOUSTIC REFLECTION
- EXTREMELY LOW FREQUENCY

# Subject Categories:

- Physical and Dynamic Oceanography
- Numerical Mathematics
- Acoustics