A unit of frequency equal to one cycle per second named after the physicist, H.R. Hertz (1857-1894). Side scan sonar frequencies generally output acoustic signals in the kilohertz (kHz), or thousands of cycles per second region. Bathymetric systems typically operate in the 20-200 kHz range, imaging side scan sonar in the 50-650 kHz range and a few special application sonar systems in the megahertz (1,000,000 Hertz) range. Hertz is also interchanged with the term “cycles” with one kilohertz being equal to one kilocycle.