A Technique to Verify Statistical Performance Requirements for Sonar Detection Systems

Abstract

An automated forced-choice method of evaluating detection performance is employed instead of the familiar fixed-threshold technique. The latter method utilizes a number of preselected, constant thresholds to estimate both detection and false alarm probabilities, whereas, the former incorporates a variable threshold with a precise false alarm probability to estimate only the detection probability. The estimate is obtained by selecting the “greatest of” a number of alternatives—one containing signal plus noise and the remainder containing noise only—to determine the number of correct detections (selection of signal plus noise alternative). The advantages of the forced-choice technique are predetermined false alarm rate, a single parameter test, less required test time, and real time monitoring of test results by minimizing the amount of data reductions. A comparison of both techniques is presented for two sets of typical statistics encountered under test conditions. Because of the uncertainty associated with the variable threshold, the forced-choice results are slightly pessimistic, but are within 0.3 dB of the fixed-threshold results. However, the forced-choice technique can easily be made equivalent to the fixed-threshold procedure by incorporating a correction factor into the test procedure. [Work supported by Naval Ship Systems Command.]