Space and time coherence of acoustic field in shallow water

New experimental measurements of signal coherence in shallow water are pres ented. For signals with low frequencies of about 500 Hz in iso-velocity sha llow water with a silt-sand bottom and a water depth of about 45 m, the ver tical coherence has no distinct depth dependence at ranges of 18.5, 55.5 an d 92.5 km, but it has obvious range dependence. The horizontal coherence le ngths are all greater than 40 wavelengths, and the time coherence lengths a re all greater than 510s at these ranges. These experimental results show t hat a low-frequency acoustic field has strong spatial coherence and tempora l stability in iso-velocity shallow water.