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 (album) Frequencies (album) Frequencies is the debut studio album by British techno duo LFO, released on 22 July 1991 by Warp. Originally released by Warp in the United Kingdom, "Frequencies" was released by Tommy Boy Records in the United States. The US edition of the album alters the track listing slightly, inserting "Track 14", which concludes the UK edition, in between "We Are Back" and "Tan Ta Ra"; the rest of the tracks then proceed in the same order as the UK edition. "LFO", "We Are Back", and "What Is House? (LFO Remix)" (an expanded version of "Intro") were released as