# Low-Pass Filter

From Audacity Development Manual

*passes frequencies below its cutoff frequency and attenuates frequencies above its cutoff frequency. This effect can therefore be used to reduce high pitched noise.*

**Low-Pass Filter****Accessed by:**

## Frequency (Hz)

Sound above this cutoff frequency in * Hz* is not eliminated but increasingly attenuated as the frequency rises further above the cutoff.

The cutoff frequency (sometimes also called *corner frequency*) defines the point at which the audio is reduced by 3 dB. Thus there will also be a small and decreasing amount of attenuation just below the cutoff frequency as in the following image.

## Roll-off (dB per octave)

Roll-off sets the steepness of the attenuation above the corner frequency. Higher roll-off values give a steeper slope to the attenuation. For example, with a roll-off of 6 dB per octave, the sound decreases by 6 dB in * amplitude* for each octave above the cutoff frequency (an octave above is double the frequency).

To achieve more attenuation, run the effect again or use a greater roll-off. |