PROBLEM TO BE SOLVED: To provide a device for detecting BVI(blade vortex interference) noise capable of detecting BVI noise with accuracy. ;SOLUTION: A microphone 11 installed on the body of a helicopter detects the noise caused by the helicopter and converts it into electric signals. These signals are amplified by a preamplifier 12, only a predetermined frequency band is extracted from them by a filter 13. And then it is sampled by an A/D converting circuit 14 and converted to digital signals. An operational part 15 searches these converted digital signals for a peak value and compares this peak value with a predetermined threshold value. In the case when the peak value is greater than the threshold value, it is judged that 'BVI noise is present'. In the case when the peak value is smaller than or equal to the threshold value, it is judged that 'BVI noise is absent'. These judgement signals are sent to a warning device 16 to issue an an alarm to a pilot or sent to a flight controlling computer 17 to control the flight that prevents BVI noise from occurring.;COPYRIGHT: (C)1998,JPO
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