To learn VoiceOver sound effects, open the VoiceOver Help menu by pressing VO-H. Then use the arrow keys to navigate to Sounds Help.
To mute VoiceOver sound effects (without affecting the audio of other apps), open VoiceOver Utility (press VO-F8 when VoiceOver is on), then click the Sound category.
If you’re using VoiceOver gestures, avoid muting sound effects. Hearing the blank space sound effect is very useful in determining where items are located on the desktop.