If you listen to music with your Mac, you may have it connected to external speakers or amplifier, as I do. By default, all the sound from your Mac will go to that external source. If you have your speakers or amplifier turned off, you won’t hear things like system beeps or alert sounds.
There’s an easy way to get around this: you can set different output for “sound effects.” This doesn’t work with all Macs, but it might with yours. Here’s how to set it up.
First, go to the Apple menu > System Preferences, and click the Sound icon. Click the Output tab, and you should see your current output selected.
Click Sound Effects. Below the section where you select an alert sound is a menu, Play sound effects through. Select here either Display Audio, if you have a display with speakers (in an iMac or other display), or Internal Speakers, if that option is available.
In my setup, I use the optical digital-out port for audio, and for some reason, Internal Speakers is not an option. But if I have a normal audio cable connected to my Mac, then that option is available. There may be other setups where you can’t set an option other than the one selected in Output; if this is your case, feel free to post a comment explaining your setup.