Change your alert sounds
When you try to do something that isn’t allowed, or if your Mac needs your input or more information, an alert message appears on your screen and an alert sound plays. You can change the alert sound and set its volume.
Before you start, open the Sound Effects pane of Sound preferences (choose Apple menu > System Preferences, click Sound, then click Sound Effects).
Choose an alert sound
Click a sound in the list.
You can also preview an alert sound by clicking it in the list.
Adjust the alert sound
You can adjust any of the following:
Change where you hear alerts: Normally you play sound effects through your computer’s internal speakers, but if another sound output device is available, you can choose it from the “Play sound effects through” pop-up menu.
Adjust the volume of alerts: Drag the Alert volume slider. The alert volume is relative to your computer’s output volume, so if you lower the computer’s volume, alert sounds also play more quietly.
Choose whether to hear user interface sound effects: Your Mac plays sound effects when you perform certain actions, such as dragging an item to the Trash. To turn off sound effects, deselect the “Play user interface sound effects” checkbox.
Choose whether to hear a sound effect when you change the volume: On some keyboards, when you press one of the volume keys, the alert sound plays to let you hear the new volume. To prevent this sound, deselect the “Play feedback when volume is changed” checkbox. To temporarily reverse this setting, hold down the Shift key as you press a volume key. (Not all keyboards have volume keys.)
To have the screen flash when an alert appears, select the option in the Audio pane of Accessibility preferences (choose Apple menu > System Preferences, click Accessibility, then click Audio).