Teens are taking their brightness to a new level by creating a ring tone with a high-frequency buzz that most adults can’t hear so they can use their phones to text-message in classrooms, according to reports in England.
    Known as “Teen Buzz” ,  it is spread from phone to phone via text messages and Bluetooth technology, Daily Mail said.
    The sound was originally used in a device (装置) called the Mosquito, which helped store owners in England repel (驱赶) teenagers from loitering (闲逛) outside their shops. The high-frequency sound is annoying for teenagers but most adults can’t hear it because over the age of 20, most adults are unable to hear that frequency (between 18 to 20 kHz). It is based on the medical phenomenon known as presbycusis, or age-related hearing loss, Mosquito manufacturer Compound Security said.
    Schoolchildren can receive calls and texts during lessons without teachers knowing what is going on. “All the kids were laughing about something, but I didn’t know what. They know phones must be turned off during school. They could all hear somebody’s phone ringing but I couldn’t hear a thing,” said a secondary school teacher in Cardiff. “One of the other children told me all about it later. I couldn’t be too cross, because it shows resourcefulness (足智多谋).”