What is a third octave?
A third octave is more like a “third of an octave”, i.e. an octave divided by three. An octave is a frequency band that spans within two frequencies with a ratio of 2:1. For instance, the 1000 Hz octave band spans from 707 to 1414 Hz. Adjacent octave bands are also spaced by a ratio of 2:1, such as the 500 and 1000 octave bands. The octave band centre frequencies have been standardised by ISO (International Organization for Standardization) to rounded figures as follows: 63:125:250:500:1k:2k::4k:8k:16k Hz A third of an octave is a frequency band that is three times smaller than an octave band, so that an octave band logically comprises three third octave bands. Thus, the 1000 Hz third octave has a bandwidth of 891-1122 Hz. And the 1000 Hz octave band encompasses the 800, 1000 and 1250 Hz third octave bands. Third octave bands are often used in audio because they relate to the way human hearing (and mammals’ in general) works. The most used form of pro-audio equaliser is the 1/3rd octav
