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
2182 kHz 2182 kHz The radio frequency 2182 kHz is one of the international calling and distress frequencies for maritime radiocommunication in a frequency band allocated to the mobile service on primary basis, exclusively for "distress and calling" operations. Transmissions on 2182 kHz commonly use single-sideband modulation (SSB) (upper sideband only). However, amplitude modulation (AM) and some variants such as vestigial sideband are still in use, mainly by vessels with older equipment and by some coastal stations in an attempt to ensure compatibility with older and less sophisticated receivers. 2182 kHz is analogous to channel 16 on the marine VHF band, but