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
Above the Influence be independent and self-sufficient", Slater said. He also mentioned the limitations of the study. These include the fact that findings regarding the ONDCP campaign were based on survey results and not a randomized, experimental design in which some youth saw the ONDCP campaign and others did not. Another limitation was that the study, while taking place in twenty communities around the U.S., did not use a random sample of U.S. youth. Above the Influence Above the Influence originated as a government-based campaign of the National Youth Anti-Drug Media Campaign conducted by the Office of National Drug Control Policy in the