Sound (built-in output) not working after Big Sur update

There could be a number of reasons why the sound on your Mac is not working after updating to Big Sur. Here are a few troubleshooting steps that may help:

1. Check the volume level: Make sure that the volume on your Mac is turned up and not muted. You can do this by clicking on the speaker icon in the menu bar or by going to System Preferences > Sound.
2. Restart your Mac: Sometimes a simple restart can fix the problem. Try restarting your Mac and see if that resolves the issue.
3. Check your sound settings: Make sure that your Mac is set to use the correct audio output. You can check this by going to System Preferences > Sound > Output and selecting the built-in speakers.
4. Check for software updates: Make sure that your Mac is up to date with the latest software updates. You can do this by going to System Preferences > Software Update.
5. Reset the NVRAM or PRAM: Resetting the NVRAM or PRAM on your Mac can sometimes fix sound-related issues. To do this, shut down your Mac and then turn it back on while holding down the Command + Option + P + R keys until you hear the startup sound twice.
6. Try using headphones or external speakers: If the sound is still not working on your Mac, try connecting headphones or external speakers to see if the issue is with the built-in speakers.

If none of these steps resolve the issue, it may be worth contacting Apple Support or taking your Mac to an authorized repair center to get it checked out.

Hi PLT05,

We'll want to make sure your iMac system default sound output is set to go to the internal speakers. If it's working on startup and in an app, it's very likely there's simply a configuration issue.

Use the steps here to make sure you choose the Internal Speakers:

1. On your Mac, choose Apple menu  > System Preferences, click Sound, then click Output.
2. Select the "Internal Speakers" in the list of sound output devices. 

Change the sound output settings on Mac

Let us know if testing the volume and alert sounds from there allow you to play using the iMac speakers.

Thanks for using the Apple Support Communities.