When Sound Check is on, iTunes scans the songs in your library and gathers information about their playback volume. When you add new songs to your library, iTunes gathers this information in the background. This data is stored in either the song's "normalization information" ID3 tag or in your iTunes Music Library. The audio data in your music files never changes. If you encode or "rip" a song from a CD, iTunes stores the sound check level in the song's ID3 tags.
When Sound Check is off, iTunes ignores the Sound Check data stored for each song, but doesn't remove it from the iTunes Music Library or the ID3 tags.
Turn on Sound Check
- Open iTunes on your computer.
- Mac: From the menu bar at the top of your computer screen, choose iTunes > Preferences.
Windows: From the menu bar at the top of the iTunes window, choose Edit > Preferences.
- Click the Playback tab.
- Select Sound Check.
- Click OK.
Sound Check works with .mp3, .AAC, .wav, and .aiff file types.
Boosts in playback volume use the built-in limiter in iTunes to protect against clipping.