After security updates, formerly silent Mojave iMac now has a startup chime

My 27-inch 2017 iMac has never sounded the startup chime in its life…until very recently.

I was fully up to date in terms of version number (10.14.6), but I had been behind on security updates, such that I still had Safari 13.

The other day, I decided to update my bootable clone and get myself fully up to date. Obviously, it updated some firmware, because my iMac, which had been blissfully silent, now has the startup chime I haven’t heard in years – not since my previous iMac.

I know that later versions of the MacOS have “brought back” the startup chime, with a setting to enable and disable it, but I am not ready to upgrade beyond Mojave just yet. That being said, how do I silence the chime again?


Those that I know of who have tried some of the old commands to do so have failed to do so. I personally have been quite pleased at it’s return, so have not tried to silence it myself.

IIRC if you mute audio before restarting, the chime will be silenced.

This should prevent it:

sudo nvram SystemAudioVolume=%80

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