octaveband

An octaveband, or octave band, is a frequency band whose upper limit is twice its lower limit, representing one octave of the frequency spectrum. In practice, an octave band covers the range from f to 2f, with f_lo being the lower bound and f_hi the upper bound. The center frequency of an octave band is the geometric mean of its ends, f_c = sqrt(f_lo × f_hi) = f_lo × sqrt(2).

Common standard octave bands used in acoustics include: 31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz. Some analyses extend to 16 kHz or beyond. These bands are widely used for spectral analysis, measurement of environmental noise, room acoustics, and audio engineering. They provide a balance between spectral resolution and measurement simplicity, because each band spans a factor of two in frequency.

In practice, octave-band levels are expressed in decibels relative to a reference sound pressure (dB SPL); measurement devices may present levels either unweighted or with weighting, such as A-weighting, depending on the application. Octave bands are distinct from, and coarser than, 1/3-octave-band analyses, which use narrower bands for greater spectral detail.

The concept is defined in international standards governing acoustic measurement, filtering, and sound level meters; standard octave-band filters ensure consistent band boundaries across equipment and studies.