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
Australian and New Zealand television frequencies allocation issue was not fixed until the late 1990s, when the FM band was expanded to the standard full 20 MHz block. As of the mid-2010s NZ totally abandoned its VHF band for UHF channels above 25. There is a frequency offset for many DTV channels between Australia and NZ, because of historical reasons relating to the introduction of PAL. DVB-T channel allocation note Table notes : Text in "italics" means these frequencies are not currently used but set aside as a Guardband or for future use. The ABC has the highest number of transmission sites: often, but not always,