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
60-meter band assignments with center frequencies 5373 kHz and 5405 kHz on a secondary non interference basis for propagation experiments with a maximum mean power not exceeding 27 dBW (500 Watts). Canada ( ITU Region 2 ): On Wednesday 22 January 2014, the Canadian regulator, Industry Canada (IC) released a decision to allow amateur radio operators to use the 5332 kHz, 5348 kHz, 5358.5 kHz, 5373 kHz and 5405 kHz (channel centre) frequencies on a no-interference, no-protection basis, 2.8 kHz bandwidth, same modes as U.S., 100W PEP maximum power. These are the same channels, modes and criteria as those available to US