Can you hear this?

The so-called Mosquito Ringtone a.k.a. Teen Buzz. This is the cell phone ringtone adults can't hear but kids can. Students use the mosquito ringtone so they can receive text messages in class and their teachers can't hear their cell phone ring.

The theory is that as we age, we lose the ability to hear high frequencies. If you don't want teen-agers loitering around your establishment, blast them with high pitched sounds that adults can't hear. If you're an enterprising young person you can use a high frequency sound as your ringtone and teachers in school
won't be able to hear it. (Your mileage may vary.)

I can ... load of guys in work here cannot.