# Low-Pass Filter

From Audacity Development 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...

## 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.

## Roll-off (dB per octave)

Roll-off sets the steepness of the attenuation above the corner frequency. Higher roll-off values give a steeper slope to the attenuation. For example, with a roll-off 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).

| To achieve more attenuation, run the effect again or use a greater roll-off.

## 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.
- OK applies the effect to the selected audio with the current effect settings and closes the dialog
- Cancel aborts the effect and leaves the audio unchanged, closing the dialog
- brings you to the appropriate page in the Manual, this page

## Links

|< Index of Effects, Generators and Analyzers

|< Effect Menu