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
Frequencies (film) "The Austin Chronicle" wrote, "What raises Fisher's script to the upper echelons of the current wave of intellectually challenging indie sci-fi ... is that it truly weaves its concept into its nature." Kurt Halfyard of Twitch Film wrote that it "is chock-a-block full of knowledge, destiny and imagination, but suffers a bit from a lack of heart and soul." Frequencies (film) Frequencies, also known as OXV: The Manual, is a 2013 independent British science fiction romance film written and directed by Darren Paul Fisher. The film stars Daniel Fraser, Eleanor Wyld, and Owen Pugh. The film takes place in a