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:

  1. Internal Speakers;
  2. Speakers on the secondary monitor; and
  3. 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?

  • Notification sounds & 'everything else' are independently assignable. Look at Audio MIDI Setup in Apps/Utilities. Headphones & HDMI will both override 'internal speakers' when connected, but may be dependant on connection order as to which wins.
    – Tetsujin
    Jun 3, 2020 at 15:55
  • I have this configured on my Macs. All system sounds come through the internal speakers and everything else through the sound device I’m using at the moment. Check your sound configuration.
    – Allan
    Jun 3, 2020 at 15:56
  • If you compare the install log and last reboot in terminal, have you done a second clean restart after applying the security updates and supplemental update?
    – bmike
    Jun 3, 2020 at 16:02
  • @Allan: I did check and it was set to 'Internal Speakers'. However, this is a setting that I never touched. So not sure how it got modified. TY, anyway. Jun 3, 2020 at 16:52

1 Answer 1


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.

Setting in System Preferences.app
(source: kumowoon1025.com)

Setting in Audio MIDI Setup.app
(source: kumowoon1025.com)

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,

  • This is exactly what I was referring to in my comment above!
    – Allan
    Jun 3, 2020 at 16:44
  • It was none of the cases you mentioned. As I said, this is a recent phenomenon. But I'll take your answer as the right one as it pointed me to something I didn't notice before. I think the sound output will be correct from now on. Jun 3, 2020 at 16:51

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