Here’s an interesting fact about ringtones with higher frequencies. With these higher frequency “mosquito” ringtones, students or young people are able to set their cellphones to be only heard by people under a certain age! Now here’s a way kids can set their phone to be audible, but not audible to the teacher, provided he’s over 30.
The short version, A tone outside the audible range of hearing for most people over the age of 30. This means that you can get phone calls and receive text messages in class or school without teachers hearing it.