# Low Pass Filter

### From Audacity 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**

## Rolloff (dB per octave)

Sets the steepness of the attenuation. Higher rolloff values give a steeper attenuation of frequencies above the cutoff frequency. For example, with a rolloff 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).

## Cutoff 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.

To achieve more attenuation, run the effect again or use a greater rolloff.