| 摘要 |
PURPOSE:To enable to make the detection of an obstacle without providing an ultrasonic wave oscillator etc. specially for detecting the obstacle by providing the first microphone and the second microphone and a detection controlling device etc. CONSTITUTION:The first microphone 2, the second microphone 3, variable frequency BPFs 7, 8, a microcomputer MC 11 and an indicator 12 etc. are provided. The MC 11 controls the frequency band of BPFs 7, 8 and reads sound pressure component at specified frequency in digital values on microphones 2, 3. It is desirable to change the setting of frequency correspondingly when sound source is different. The MC 11 calculates a spectral pattern and average sound pressure level from sound pressure component data of the microphone 2. It extracts the component of the microphone 3 basing on this and obtains an average sound pressure level. Then, the average sound pressure level of the microphone 3 is divided by the average sound pressure level and quotient is obtained. The quotient is compared with a specified value, when it is large, it is judged that there is an obstacle, and when small, judged as there is no obstacle.
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