# Low Pass Filter

### From Audacity Manual

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

  Accessed by: Effect > 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.

## Links

> Forward to: Notch Filter

< Back to: High Pass Filter

|< Effect Menu

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