Normalize

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• Ed 10Jun11 proofed & all links verified intact

Use the Normalize effect to set the maximum amplitude of single or multiple tracks, equalize the peak volumes of the left and right channels of stereo tracks and optionally remove any DC offset from the tracks.

Accessed by: Effect > Normalize...

Remove any DC offset

When this box is checked Normalize will attempt to remove any DC offset in the selection by centering the waveform on the 0.0 amplitude level. Technically, it does this by finding the average of all the sample values in the selection, then subtracting that average value from all the samples. Removing any DC offset is desirable as its presence can cause clicks when playing or editing, but will slow down the Normalize effect to some extent.

Failure to remove DC offset can also limit the headroom available for the amplitude normalization and can thus restrict the loudness that you achieve.

Bill 10Jun11: ToDo-2 I'm not sure the following is true. I have not been able to create an asymmetrical waveform where DC offset removal fails.

This works well on long selections containing a mix of sounds, but may actually create DC offset when applied to short sections of recordings of voices or certain instruments that have an inherently asymmetrical waveform.

Normalize Maximum Amplitude to

Enter the value for the maximum amplitude you would like the processed selection to have. Normalize initializes to -1 dB on first use for all users from 1.3.13 Beta or earlier, but your choice of settings will be remembered thereafter. A level of -1 dB is just below the maximum amplitude (0 dB) possible without clipping, but gives a little headroom for effects and distortion-free playback on all equipment. Enter a greater negative value (for example, -3 dB) to normalize to lower amplitudes.

Entering a positive value is disallowed and causes the "OK" and "Preview" buttons to be disabled. Use Effect > Amplify if you need to increase amplitude above the 0 dB clipping level.

Peter 13Jun11: Is -3 really a "greater" negative value than 0 or -1, I would have thought it was "lesser" "or lower". I personally would prefer "lower" for clarity and the avoidance of doubt (it echoes the "... to lower amplitudes").

Steve: "more negative"?

Normalize stereo channels independently

When this box is unchecked (the default), Normalize will work on the channels of a stereo track as a pair and change the level of both channels by the same amount. Use this if your audio is already correctly balanced as this mode will preserve its original stereo balance.

When this box is checked, Normalize will adjust the amplitude separately for the left and right channels of a stereo track. This is useful for correcting stereo recordings of LPs and cassettes which may be unbalanced, as long as significant clicks are removed first.

Tips

Normalizing multiple audio tracks
If you select multiple tracks and apply the Normalize effect, then all audio tracks will be independently normalised to the same peak level.

For example, if you set "Normalize Maximum Amplitude to:" 0.0 dB, every selected audio track will be normalized to 0.0 dB, irrespective of its original level. Whatever peak volume differences there were between the tracks will be removed.

Difference from the Amplify effect
With Amplify, if you select multiple tracks and apply the effect, then all audio tracks will be amplified by the same amount thus preserving the balance between the tracks.

Normalize offers the option to remove DC offset, Amplify does not offer that option. Normalize does not allow clipping above 0 dB, but Amplify does.

For a more thorough discussion of differences between the Amplify and Normalize effects, see this page in the Audacity wiki