Normalize audio files
Normalization is a process that raises the maximum level of a digital signal to a specified amount—typically to its highest possible level without introducing distortion.
In the Audio File Editor, you can set the maximum level (as a percentage or in decibels) in one of the “Peak at” fields in the Function Settings window (choose Functions > Settings or click the Settings button in the Normalize dialog).
These settings are automatically stored in Logic Pro preferences when the application is closed, and they apply to all projects.
Tip: You should not choose 100% (0 dB) in these fields, as this may result in clipping if you need to increase the gain (with an EQ, for example) of the overall signal later in the production process. A good rule of thumb is to reserve 3 to 6 dB of headroom or more, to allow for further audio processing tasks, such as mixing and effects processing.
Normalize the selected area of an audio file
Choose Functions > Normalize from the Audio File Editor menu bar (default key command: Control-N).
Logic Pro X locates the point with the highest volume in the selected area, and determines how far it is from the maximum possible level. The level of the selected area is then raised by this amount. The dynamic relationships of sample levels within the audio passage remain unaltered.
Tip: The start and end points for the section being normalized should generally not fall within a continuous section of audio, as this will result in abrupt increases in volume after normalization. The start and end points should therefore be located in sections that occur just after, or before, musical gaps.