Octave Filter

A filter whose upper-to-lower pass band limit bears a ratio of 2. Is is best centered at one of the preferred frequencies given in ISO R266. Octave filters are used to make a real-time frequency analysis. These filters are called constant percentage bandwidth (CPB) filters. Octave filters can be divided into 1/3-, 1/12- or 1/24-octave filters, depending on the required resolution.