The audio spectrum, also called the audio bandwidth, is the audible frequencies of human hearing, which generally occur between 20 Hz and 20,000 Hz (20 kHz). The audio spectrum is sometimes broken down into the following ranges: bass (20 Hz to 140 Hz), upper bass (140 Hz to 350 Hz), midrange (350 Hz to 2.5 kHz), upper midrange (2.5 kHz to 5 kHz), and high end (5 kHz to 20 kHz). These frequency ranges are not exact and are sometimes broken at 150 Hz, 400 Hz, 2 kHz, and 6 kHz.