Frequency spectra are most commonly represented by frequency bands rather than single frequencies. Frequency bands are defined ranges of frequencies. The most common frequency bands are octave bands. As is the case in music, an octave is described as the range between a given frequency at the low end and doubling of that frequency at the high end. In this illustration, the lowest octave shown ranges from 200 hertz to 400 hertz. The next octaves are from 400 hertz to 800 hertz, 800 hertz to 1.6 kilohertz, and 1.6 kilohertz to 3.2 kilohertz.