For certain acoustical measurements, a constant-frequency increment is a suitable spacing. More commonly, however, a constant-percentage increment is adopted and the frequencies then form a geometric series. This is useful as acoustical data is commonly plotted on a logarithmic frequency axis (see IEC 60263). This standard deals with the geometric series.
The present standard is not concerned with specification of preferred frequencies for music or musical instruments, or with the calculation of band-edge frequencies for bandpass filters.