# High Pass Filter

### From Audacity Manual

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

**High Pass Filter**

## Rolloff (dB per octave)

Sets the steepness of the attenuation. Higher rolloff values give a steeper attenuation of frequencies below the cutoff frequency. For example, with a rolloff of 6 dB per octave, the sound decreases by 6 dB in * amplitude* for each octave below the cutoff frequency (an octave above is double the frequency).

## Cutoff frequency (Hz)

Sound below this cutoff frequency in * Hz* is not eliminated but increasingly attenuated as the frequency falls further below 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 above the cutoff frequency as in the following image.

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