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
Citizens band radio country; use of foreign equipment may be illegal. However, many countries have adopted the American channels and their associated frequencies, which is generally in AM mode except some higher channels which are sometimes in SSB mode. The standard channel numbering is harmonized through FCC (America) and CEPT (Europe) . See also channel assignments for CB usage in the United States. When looking at the FCC/CEPT channel list there are some channels with an offset of 20 kHz instead of the regular 10 kHz step. These intermediate frequencies are reserved for the Radio Control Radio Service (RCRS) (formerly known as the