| 摘要 |
An apparatus for reducing the presence of birds, particularly in airport areas, characterised by comprising: at least one amplitude modulator (61, 62) controlled by at least one generator (41, 43, 44) of carrier frequency (f1, f3, f4) and at least one generator (42, 45) of modulating frequency (f2, f5); at least one frequency modulator (63) controlled by at least one generator (46) of carrier frequency (f6) and at least one generator (47) of modulating frequency (f7); a mixer (8) for the output signals (141, 143, 143) of said amplitude modulators (61, 62) and frequency modulator (63); control means (161, 162, 163) for the input signals (141, 142, 143) to the mixer (8); a controlled gain amplifier (10) for the output signal (18) of the mixer (8); a power amplifier (11), fed by said controlled gain amplifier (10); at least one electro-acoustic transducer (13) fed by the output signal of said power amplifier (11); and a control unit (2) acting in random manner on the frequency (f1, f2, f3, f4, f5, f6, f7) of at least one frequency generator (41, 42, 43, 44, 45, 46, 47), on the input signals (141, 142, 143) of said mixer and on the gain of said controlled gain amplifier (10). |
