Array measurements and characterizations with relative velocity as a parameter

Space and time are usually treated as independent random variables with assumed ergodicity; however, dynamic sound fields are produced by moving sources in a multipath/modal sound channel. Can the velocity and range of a source be utilized in a space-time processor to increase gain, cancel noise and improve resolution? This paper summarizes experiments performed with horizontal arrays and processing which used source-receiver relative velocity as a processing variable, that is space-time processing. Results obtained in a shipping noise field showed the relative velocity acted as a filter that improved the signal-to noise ratio for sources with known relative velocity but reduced it for sources having unknown or mismatched relative velocities. A shallow water experiment conducted with a vertical array, moving source, and Hankel Transform processing showed that the depth dependent horizontal wavenumber spectra were measurable when source position and velocity were known and comparable to calculated spectra in both amplitude and phase. Thus, measurement and cancellation of moving surface ships is possible and enhanced if the relative velocity is known. In addition if the region in the vicinity of the measurement array is known; the dynamic modal variations can be adaptively modeled.