James V. Candy
Lawrence Livermore Natl. Lab., Univ. of California, P.O. Box 808, L-495, Livermore, CA 94550
Edmund J. Sullivan
Naval Undersea Warfare Ctr., Newport, RI 02841
Most acoustic sources found in the ocean environment are spatially complex and broadband. When propagating in a shallow ocean these source characteristics complicate the analysis of received acoustic data considerably. On the other hand, each of the narrow-band lines composing the broadband source spectrum can be considered multiple observations which can be used to enhance signal levels. The usual approach is to process each line separately and combine the results to achieve more enhancement at the array than that which could be utilized for a single temporal frequency. The enhancement of broadband acoustic pressure-field measurements using a vertical array is discussed. Here the model-based approach is developed for a broadband source using a normal mode propagation model. It is well known from propagation theroy that a different modal structure evolves for each temporal frequency line; thus it is not surprising that the model-based solution to this problem results in a scheme that requires a ``bank'' of model-based processors---each processing its own underlying modal structure for the narrow frequency band it operates over. It is shown how this broadband processor can be implemented in pseudo-real-time due to its underlying parallel structure.