Low Pass Filter - Audacity Manual

# 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.

## The buttons

Clicking on the command buttons give the following results:

- Manage gives a dropdown menu enabling you to manage presets for the tool and to see some detail about the tool. For details see Manage presets.
- Preview plays a short preview of what the audio would sound like if the effect is applied with the current settings, without making actual changes to the audio. The length of preview is determined by your setting in Edit > Preferences > Playback, the default setting is 6 seconds.
- Debug applies the effect to the selected audio with the current effect settings, but unlike OK the effect runs in debug mode. This is primarily of use when writing or editing Nyquist plug-ins.
  - In addition to the normal plug-in behavior, a "debug window" opens to display error messages, normally the debug window will be empty.
- OK applies the effect to the selected audio with the current effect settings.
- Cancel aborts the effect and leaves the audio unchanged.

## Links

|< Index of Effects, Generators and Analyzers

|< Effect Menu

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