Text: [ACOUSTICS] Octave and one-third octave band center frequencies are the geometric means of their respective lower and upper limits as defined by ISO and ANSI standards.The upper and lower nominal octive band limits are arrived at by multipling the center frequency by 1.4142 and 0.7071 respectively. One-third band center frequencies are given by 10n/10 where n is the one-third octive band number. For instance, for 125 Hz the band number is 21 and 102. 1 = 125.89. Lower and upper frequency limits are a function of 2-1/6 or (0.89) and 21/6 or (1.12) respectively.

See Also:

Source: 85