## 4pSP7. Broadband acoustic-field image enhancement in a noisy shallow ocean.

### Session: Thursday Afternoon, December 5

### Time: 3:50

**Author: James V. Candy**

**Location: Lawrence Livermore Natl. Lab.**

**Author: E. J. Sullivan**

**Location: Naval Undersea Warfare Ctr., Newport, RI 02841**

**Abstract:**

When a narrow-band source propagates in a shallow ocean environment, the
ocean can be characterized by a waveguide resulting in a normal-mode solution.
When the source is broadband, its spectrum can be decomposed into a set of
distinct narrow-band lines, each supporting a distinct set of normal modes
differing from frequency to frequency by both the number of modes and their
respective wave numbers. Couple this propagation problem to a set of noisy
hydrophone measurements obtained from a vertical array of sensors spanning the
water column and a formidable problem in estimating the broadband acoustic field
results. The field itself is essentially a space--frequency and once this
space--frequency field can be estimated from the noisy measurements, then
various postprocessors can be applied to estimate, detect, and localize the
underlying source. Thus it is important, in the broadband case, to extract and
enhance the broadband acoustic-field image. In this paper the development of a
model-based image enhancement technique is discussed which employs the broadband
normal-mode solutions using an optimal estimation scheme to provide the required
enhancement. A by-product of the outputs of the processor, which is a
space-varying Kalman filter, is the ability to not only enhance the image, but
also to extract and enhance the corresponding broadband modal functions (one for
each frequency) as well.

ASA 132nd meeting - Hawaii, December 1996