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
European cable television frequencies band. In most cable networks, the UHF band is unusable because its frequency is too high, so TV stations are only allocated within Band I, III, the Mid-, Super- and Hyperband. Even in modern cable networks, only some UHF channels (like only channels 21-26) may be usable. This leads to a high level of congestion in many European cable TV networks, especially as analogue transmission, which is still commonplace in cable television in Europe, is being migrated to digital transmission. European cable television frequencies These tables detail the frequencies used in European cable networks. Cable networks use frequencies which are