macOS 10.15.5 screwed up Sound Output device I've noticed it only as soon as yesterday, so I'm going to pin it on the latest macOS release, i.e. 10.15.5.

The sound output is unreliable in the latest update. I have three output devices in my setup:


Internal Speakers;
Speakers on the secondary monitor; and
Plugged-in headphones.


Yesterday I saw that both my headphones as well as internal speakers were engaged simultaneously. Meaning, I was listening to music on the headphones and some alarm sounds (like the sound that plays when you have hit the end of current line in Terminal etc.) would come through internal speakers.

Today I noticed that the audio from a monitor is coming from the secondary monitor's speakers while message notification sound came off the internal speakers.



Is anyone else seeing something similar?

Is this something that would be / need to be fixed or has Apple had some better understanding of sounds output and decided to engage multiple outputs at the same time?
This has been a feature of Mac OS X as far back as I can remember.

You can set the system alert sound device separately from the device the main audio output (for "regular audio", such as music, audio track of movies, non-system-alert-api application sound) uses.



It might be you only noticed this now because maybe your internal speakers weren't functional before the update, and you didn't notice because you didn't use them too often? But that's just a wild guess.

Might be relevant: the release notes for macOS Catalina 10.15.5 mentions:


  Addresses an issue for Mac computers with the Apple T2 Security Chip
  where internal speakers may not appear as a sound output device in
  Sound preferences


I think you might have been having the above mentioned issue, and the internal speakers weren't available as an output device,