| 摘要 |
PROBLEM TO BE SOLVED: To remove only marine organism noises of cries of dolphins, etc., in a simple process by calculating a standard deviation value of signal levels for every predetermined angle azimuthal distance, calculating and displaying an average value of signal levels of reception signals from which an input reception signal of the signal level not lower than the deviation value is removed. SOLUTION: A signal 11 detected by a wave receiver sensor 10 set on a vessel or the like is inputted to a delay phasing circuit 12-i and converted into a reception signal 13-i having a directivity in the horizontal direction. The conversion is carried out with a shorter cycle than the cycle of cries of dolphins, etc. The signal is inputted to the marine organism noise removal circuit 14-i and, the standard deviation value is calculated for a fixed time at a standard deviation value calculation part. The value is compared with a constant value at a comparator part. When the value is detected to be not smaller than the constant value, the reception signal 13 is judged to include marine organism noises, and the reception signal output from a selector is processed through a noise removal process. When the deviation value is smaller than the constant, the noise removal process is not carried out and input to an integration circuit 16-i after an average value of the signal 13 is calculated at an average value calculation part for a fixed time.
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