Abstract:
If the velocity-depth profile in a deep ocean has a well
defined minimum at finite depth then acoustic signals of high
enough frequency are trapped in an associated sound channel and
propagate with relatively little attenuation over large distances.
The problem considered is the inverse one of determining the
velocity-depth profile given sound channel observations. This is
an inverse eigenvalue problem in which the eigenvalue data
(typically group velocity) depends on the frequency as an
auxilliary parameter, and the inversion is rescued from the
characteristic extreme illconditioning of the inverse eigenvalue
problem by sampling in the frequency domain. However, the
inversion appears to have the unusual characteristic that if a p
parameter model is to be determined then observations are required
on at least p propagating modes.