| 摘要 |
PCT No. PCT/EP86/00009 Sec. 371 Date Oct. 7, 1986 Sec. 102(e) Date Oct. 7, 1986 PCT Filed Jan. 11, 1986 PCT Pub. No. WO86/04485 PCT Pub. Date Aug. 14, 1986.For scaring birds, at least two acoustic signals are generated whose frequencies are periodically modulated within a range between about 30 and 9000 Hz, the modulation period ranging between about 0.01 and about 5 seconds. The signals differ in the frequency modulation range, in the modulation period and/or in duration. The signals are emitted either in fixed or in arbitrary sequence.
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