# High Pass Filter

### From Audacity Manual

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

  Accessed by: Effect > 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.

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