Degradation of coherence and correlation when sound from a moving source is reflected from solid surfaces
Date
1981
Authors
Hutton, James Patrick
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Abstract
The propagation of a sound in ice-covered Arctic waters is complicated by the sound's repeated encounters with the under surface of the ice. This study addresses itself to sound propagation in the Arctic by investigating the influence of model reflecting surfaces on the coherence and cross correlation of sound, transmitted from a moving source and received by two remotely located sensors.
The signals from the sensors, for different reflecting surfaces, are processed in real time by a commercial spectrum analyser to determine which factors degrade the coherence most severely. The study shows that, when the sound reaches the sensors by reflection from an irregular solid surface, the degradation may be attributed to changes in the Doppler shifted components of the sounds at the sensors and to changes in acoustic interference patterns. In addition, the study compares cross correlation and coherence and concludes that the effects of the irregular reflecting surface may be less severe for cross correlation.