Spectral edit shelves - Audacity Manual

# Spectral edit shelves

### From Audacity Manual

The Spectral edit shelves effect is used with a Spectral Selection to apply either a low-shelving filter or a high-shelving filter to the selection, depending on the type of selection made.

  Accessed by: Effect > Spectral edit shelves...

A shelf filter curve is flat at both ends rather than flat only at the frequencies being passed. Use these filters when you don't want to reduce the lowest bass or highest treble frequencies in the spectral selection as much as you would with a standard high pass or low pass filter, or if you actually want to boost either the low or high frequencies respectively.

Depending on how the track is displayed and what spectral selection has been made, this effect will do one of the following:

- When the track is not in spectrogram or spectrogram log(f) view an error message will be displayed
- When the spectral selection begins at 0 Hz this effect applies a low-frequency shelving filter with the half-gain frequency (the mid-point of the gain section of the curve) defined by the upper frequency of the spectral selection. The gain control sets the amount of low-frequency boost or cut. This is similar to adjusting the bass control on a stereo.
- When the spectral selection ends at the Nyquist frequency of the track this effect applies a high-frequency shelving filter with the half-gain frequency defined by the lower frequency of the spectral selection. The gain control sets the amount of high-frequency boost or cut. This is similar to adjusting the treble control on a stereo.
- When the spectral selection has a center frequency, and upper and lower boundaries this effect applies both low- and high-frequency shelving filters. In this case the half-gain frequency of the low shelf filter is defined by the lower frequency boundary of the spectral selection and the half-gain frequency of the high shelf filter is defined by the upper boundary of the spectral selection. The gain control sets the amount of boost or cut between the two frequencies.
- When the spectral selection begins at zero Hz and ends at the Nyquist frequency the error message "Please select frequencies" will be displayed

| Due to a limitation in Nyquist effects, the effect dialog will be displayed before any error message.

## Examples

### Low-shelving filter

In the following example the spectral selection had a lower boundary of 0 Hz and an upper boundary of 500 Hz. In the Spectral edit shelves dialog, the Gain was set to -20 dB.

### High-shelving filter

In the following example the spectral selection had a lower boundary of 5000 Hz and an upper boundary of the Nyquist frequency of the track. In the Spectral edit shelves dialog, the Gain was set to -20 dB.

### Combined low-shelving and high-shelving filters

In the following example the spectral selection had a lower boundary of 200 Hz and an upper boundary of 10000 Hz. In the Spectral edit shelves dialog, the Gain was set to -20 dB.

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