It works by emitting a sound at high frequency (18kHz, 20kHz or
22kHz), which is unpleasant for most of biting mosquitoes, and thus
they will avoid the area where they hear this sound. These frequencies
are above the auditory spectrum of human hearing, so we do not
perceive any sound running the application.

It is not 100%% reliable method, but is easier and cheaper to prevent
mosquitoes bites.

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