# Constant Percentage Bandwidth Filter

A band-pass filter whose bandwidth is a constant percentage of centre frequency.

1/3 octave filters are constant percentage bandwidth, this is 23.1% of the 1/3 octave centre frequency.

Note that it makes sense to plot constant percentage bandwidth data on a logarithmic frequency axis.

1/3 octave data plotted on a linear frequency scale.

1/3 octave data plotted on a logarithmic frequency scale.

**See also: **Electronic Filter, Octave.

**Subjects: ** Noise & Vibration Signal Processing