High Frequency

I can play the sound of 1hz ~ 999khz, the frequency of the 12 species
It is said that frequency of sound heard by human beings and 20Hz ~ 20,000Hz, but the frequency of all you hear is you?

As a dog whistle By way of bait while sounding,
Convenience store has been utilized as a hang out measures unpleasant high frequency.
There is also a theory that good for mosquitoes and cockroaches.