Statistical normalization of non-Rayleigh reverberation
Low-frequency active sonar systems operating in shallow water are primarily limited by reverberation.Reverberation is traditionally assumed to follow a Rayleigh probability distribution, from which thedetector and other signal processing algorithms are developed. Experimental studies have shown thatreverberation can be non-Rayleigh distributed with varying statistical character over range andbearing. In such a situation, detectors designed under a Rayleigh assumption will exhibit increasedand varying false alarm performance. This report develops a technique for dealing with the unknown and varying reverberation statistics by using a non-Rayleigh reverberation model to perform a statistical normalization of the background reverberation. In this manner, range-bearing images will beproduced that have a constant background reverberation distribution (i.e., Rayleigh). The technique is evaluated through simulation, with particular attention to the false alarm performance, which is seento depend on the severity of the non-Rayleighness of the reverberation and the amount of data usedto estimate the parameters of the reverberation model. Application to real data has shown that a largedegree of the non-stationarity of the range-bearing image can be removed by statistical normalization.
Abraham, Douglas A.