| 摘要 |
PURPOSE:To improve the ability in sound detection over the entire frequency band including a hardness-of-hearing band by multiplying or demultiplying a hardness-of-hearing frequency band signal to convert the result to an audio frequency. CONSTITUTION:A device which detects whether a sounding or moving body is present or not by a Doppler frequency from the body is provided with a BPF1 which passes signals of low frequency bands F1 and F2 among frequency bands F1-F6 of sound input signals, a BPF2 which passes signals of audio frequency bands F3 and F4, and a BPF3 which passes signals of high frequency bands F5 and F6. The output FL of the BPF1 is inputted to a frequency multiplying circuit 4 to generate a signal FL' of an integral multiple of the frequency. The output FH of the BPF3 is inputted to a frequency demultiplying circuit 5, which outputs a signal FH' of frequency reduced to the audio frequency range. The signal FL', output signal of the BPF2, and signal FH' are mixed by a synthesizing circuit 6 to generate a sound out of as a composite wave, allowing audible sound detection over the entire range of frequencies F1-F6. |
