Compound Security Systems Ltd. of Britain has invented a new ring tone, which apparently can nor be heard by adults, because of its high frequency.

The ring tone is created using a frequency around 17 kilohertz – a range that is audible to relatively undamaged young ears but generally harder to hear for those older than 20.

So here is a new teen repellent – kids all over the world use this ring tone in class rooms, where mobile phone use is forbidden.

Here is a sample of the ring tone. Because of the lower sound quality for the MP3 file most people can hear the tone, therefore use the WAV version which is available here.