by 
Psycat39
ANSWERS: 3
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Ultrasonic sound, which, the theory is, that mice, bats and bugs can't stand the noise. Of course, it's above the range that humans can hear.
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not sure, i got pest repellers that were mouse repellers plus bedbug repellers, months later i still had the bedbugs, now i dont have a bed thanks to them, i dont think they work to be honest
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Some do especially the ones that cycle on and off
pearllederman 
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