Space‐time processing, environmental‐acoustic effects

The processing of acoustic waveforms by arrays requires an understanding of the temporal and spatial characteristics of signal and noise fields. Temporal and spatial processing schemes are analogous transforms that can employ a variety of windows (such as Hann, Hamming, etc.). However, the ocean environment is a filter that introduces variability to a signal in both spatial and temporal domains. This randomness is superimposed on an ambient sound channel characteristic. In the case of static source and receiver combinations, the limits on horizontal broadside array resolution are due to volume scattering and surface scattering as long as the time scale is less than the signal correlation time. However, in the case of a moving source‐receiver, the temporal and spatial scales are coupled through the sound channel characteristic and the fluctuation effects due to multipath or modal variations must also be considered. This paper reviews fundamental environmental effects and their influence on arrays in the de...