Normalizing Audio

Process Menu

The Normalize dialog allows you to raise the volume of a selection so that the highest level sample reaches a user-defined level. Use normalization to ensure you are using all of the dynamic range available to you without clipping. To display this dialog, choose Normalize from the Process menu.

When normalizing stereo data, if the selection includes both channels, normalization is computed on the loudest sample value found in either channel and the same gain is applied to both. If a single channel is selected, normalization will effect only that channel.

When converting to compressed formats, you'll achieve the best results if the audio has been normalized before the conversions occur.

What do you want to do?

Normalize using a peak value

When you normalize to a peak value, you can specify the level to which the maximum detected sample value will be set. Sound Forge applies a constant gain to the selection to bring the peak to this level.

  1. From the Process menu, choose Normalize.

  2. Click the Peak level radio button.

  3. Click the Scan Levels button.

When previewing, the entire file must be scanned--even when previewing a small selection. Clicking the Scan Levels button stores the current Peak and RMS values. This allows you to preview different Normalize to level settings without rescanning the entire file.

  1. Drag the Normalize to fader to specify the level to which the highest peak should be set.

  2. Click the OK button.

Normalize using average RMS power Available only in Sound Forge

When you normalize using average RMS power, Sound Forge will normalize the sound file using the detected average RMS value of the sound file to a value you specify. This is helpful for matching the apparent loudness of different recordings.

  1. From the Process menu, choose Normalize.

  2. Click the Average RMS power radio button.

  3. Click the Scan Levels button.

When previewing, the entire file must be scanned--even when previewing a small selection. Clicking the Scan Levels button stores the current Peak and RMS values. This allows you to preview different Normalize to level settings without rescanning the entire file.

  1. Drag the Normalize to fader to specify the new average RMS power for the selection.

When using RMS levels, set the Normalize to fader to 6 dB or less. Normalizing to 0 dB boosts the signal so that it has the same apparent loudness as a 0 dB square wave, meaning incredibly loud. If you were to do so, all of the dynamic range of the signal would be squashed and all the peaks would either be clipped or seriously compressed. The lesson is, normalizing a peak to 0 dB is OK, but normalizing RMS to anything above -6 dB can compromise sound quality.

  1. Adjust scan settings:

Item

Description

Ignore below

Drag the fader to determine the level of material you want to include in the RMS calculation. Any sound material below the threshold will be ignored in the calculation. This is useful to eliminate any silent sections from the RMS calculation. You should set this parameter a few dB above what you consider to be silence.

If you set this value to minus infinity, all sound data will be used. If the value is set too high (above -10 dB), there is a good chance that the RMS value is always below the threshold. In this case, no normalization will occur. Therefore, it is good to test the threshold by using the Scan Levels button.

Attack time

Specify how quickly the scan should respond to transient peaks in the sound file. A slower attack time will tend to ignore fast-peaking material.

Release time

Specify how quickly the scan should stop using transient peak material after it has begun to drop in level. A slower release time will increase the amount of material included in the RMS calculation.

Use equal loudness contour

Select this check box if you want the RMS calculation to compensate for high- and low-frequency audio. Very low and high frequencies are less audible than mid-range frequencies.

  1. Select an option from the If clipping occurs drop-down list:

Item

Description

Apply dynamic compression

Any peaks that would clip are limited to below 0 dB using nonzero attack and release times to minimize distortion. In other words, a time-varying gain is used to ensure that no hard clipping occurs.

This option is useful for getting very loud, yet clear sound during the mastering process.

Normalize peak value to 0 dB

The selection’s peak amplitude level is normalized to 0 dB. This applies the maximum possible constant gain that doesn’t clip to the selection. Less gain is applied than would be necessary to achieve the Normalize to RMS level.

Ignore (saturate)

Sound data is allowed to clip. Use this option only if the clipping samples are very short and infrequent.

Stop processing

Any sound data that would clip causes the Normalize function to stop processing and display a notification.

  1.  Click the OK button.

Normalize using levels from another selection or file

  1. Select the data you want to use to normalize your data.

  2. From the Process menu, choose Normalize.

  3. Click the Scan Levels button.

  4. Close the Normalize dialog.

  5. Select the data you want to normalize.

  6. From the Process menu, choose Normalize.

  7. Select the Use current scan level check box. The selection is normalized to the level displayed in the Peak or RMS fields without rescanning.

For more information about using processing dialog controls, click here.