Ultrasound independent Advisory Group on Non-ionising Radiation (AGNIR) produced a report in 2010, which was published by the UK Health Protection Agency (HPA). This report recommended an exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above). Ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000
The Mosquito into a mobile phone ringtone, which could not be heard by teachers if the phone rang during a class. Mobile phone speakers are capable of producing frequencies above 20 kHz. This ringtone became informally known as "Teen Buzz" or "the Mosquito ringtone" and has since been sold commercially. The Mosquito won the Ig Nobel for Peace in 2006. The Ig Nobels celebrate the quirkier side of serious scientific endeavour, honouring "achievements that first make people laugh, and then make them think". The German Federal Institute for Occupational Safety and Health stated in a report on The Mosquito, entitled ""Use of