| 摘要 |
PROBLEM TO BE SOLVED: To obtain an apparatus and a method for a passive sonar in which a noise can be removed optimally, even when the frequency characteristic of the noise generated by a passing ship or the like having a bed influence on the detection of a target signal is not uniform. SOLUTION: The frequency band of an acoustic signal from a receiving part is limited by a noise-level measuring part 1. The noise level in every direction of the acoustic signal in the limited frequency band is measured. Noise level data in every direction is outputted. On the basis of the noise level data and on the basis of reception level data which os calculated by a signal-level calculation part 2, a direction in which an S/N ratio becomes maximum is calculated by a direction calculation part 3 so as to be outputted as direction data. On the basis of the direction data, a directivity pattern is formed by directivity formation parts 5L, 5M, 5H in the direction in which the S/N ratio becomes maximum, and a target is searched.
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