APL - North Pacific Acoustic Laboratory

The ultimate limitations to the performance of long-range sonar are due to ocean sound speed perturbations and the characteristics of the ambient acoustic noise field. Scattering and diffraction resulting from internal waves and other ocean processes limit the temporal and spatial coherence of the received signal, while the ambient noise field is in direct competition with the received signal. Research conducted in the North Pacific Acoustic Laboratory (NPAL) program at the Applied Physics Laboratory (APL-UW) and the Scripps Institution of Oceanography (SIO) is directed toward a complete understanding of the basic physics of low-frequency, long-range, broadband acoustic propagation, the effects of environmental variability on signal stability and coherence, and the fundamental limits to signal processing at long-range imposed by ocean processes. The long-term goal of NPAL is to optimize advanced signal processing techniques, including matched field processing and adaptive array processing methods, based upon knowledge about the multi-dimensional character of the sound and noise fields and their impact on long-range ocean acoustic transmissions.