An octave band is a frequency band that spans one octave. In this context, an octave can be a factor of 2 or a factor of 10^0.3. 2/1 = 1200 cents ≈ 10^0.301. Fractional octave bands such as 1⁄3 or ​1⁄12 of an octave are widely used in engineering acoustics.

Octave band analysis is often used in noise control, hearing protection and sometimes in environmental noise issues.

Real-time octave band analyzers are special sound level meters that divide noise into its frequency components. Electronic filter circuits are used to divide the sound or noise into individual frequency bands.

Dewesoft offers flexible octave band analyzers for any sound measurement.

CPB filter is a filter whose bandwidth is a fixed percentage of a center frequency. The width of the individual filters is defined relative to their position in the range of interest. The higher the center frequency of the filter, the wider the bandwidth.

The widest octave filter used has a bandwidth of 1 octave. Many subdivisions into smaller bandwidths are often used. The filters are often labeled as Constant Percentage Bandwidth filters.

A 1/1-octave filter has a bandwidth of close to 70% of its center frequency. The most popular filters are perhaps those with 1/3-octave bandwidths. One advantage is that this bandwidth at frequencies above 500 Hz corresponds well to the frequency selectivity of the human auditory system.

Dewesoft CPB solution supports up to 1/24-octave bandwidth.

A human ear doesn't have an equal "gain" at different frequencies. We will perceive the same level of sound pressure at 1 kHz louder than at 100 Hz. To compensate for this "error", we use frequency weighting curves, which give the same response as the human ear has.

The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A, B, C, and D weighting as defined in the IEC 61672 standard.

Unweighed measurements of sound pressure do not correspond to perceived loudness because the human ear is less sensitive at too low and high frequencies. The curves are applied to the measured sound level, by the use of a weighting filter in a sound level meter.