Boot Chime stuck on loud!

[Jas-Singh685]

So I attempted to install Big Sur Beta on my external USB stick. Long story short it was taking too long (perhaps even froze) so I abandoned the install and booted back into Catalina on the internal drive.

Now however, I get a really loud startup chime. I understand Big Sur has this feature, which is great. I had previously used the sudo nvram BootAudio=%01 command to enable it.

Before, i could adjust the volume using the main OS setting, to have it quiet but audible. Now however, it does not respond to it. And it's stuck on at least 50% volume. The Catalina OS could be on lowest, or max, the chime is so loud! I can only mute the chime from the OS or terminal, it just doesn't respond to volume.

I've tried an NVRAM reset to help revert to default, but it doesn't help. (I know I'm doing it correctly because the AutoBoot gets re-enabled, which i disable). I know it was the Big Sur install that's done this, since as soon as it booted from the USB, began the loud chime. I've tried reinstalling Catalina too.

Anyone have any clue as to what I can do to restore this back to factory and I can regain control again? I love the chime but not when it wakes the house!

The machine is a 13" 2020 MacBook Pro. I apprechiate any help!

 

[anshuvorty]

Yeah, I have this issue too.

 

[chscag]

Try this:

sudo nvram StartupMute=%00

That should turn it off and afterward you can try turning it on again from the terminal.

 

[Jas-Singh685]

Try this:

sudo nvram StartupMute=%00

That should turn it off and afterward you can try turning it on again from the terminal.

Thanks for this, unfortunately this didn't make any difference at all. It seems I can't even mute it from the terminal, it only can be muted from the OS speaker setting, but still doesn't respond to volume!

I'm confused because previously an NVRAM reset would disable the chime, as per default for my machine. But now, it doesn't. It's like Big Sur has overwritten something that even a Catalina re-install hasn't restored. I'm beginning to think it's permanent until I upgrade...

 

[chscag]

It appears that the Beta of Big Sur may have messed with the firmware? A nvram reset should have turned it off and same with the terminal command above.

 

[Jas-Singh685]

It appears that the Beta of Big Sur may have messed with the firmware? A nvram reset should have turned it off and same with the terminal command above.

That was exactly my thoughts, if an NVRAM doesn't restore to default, I know something else is wrong, something I'll have no idea how to even start with. I'm hoping one of you guys might have more experience with this kind of thing

The fact a Catalina reinstall doesn't help, could it be something corrupted?

 

[Eugine]

Lauch the terminal：

step 1. sudo nvram StartupMute=%01
step 2. sudo nvram SystemAudioVolume="％80" or sudo nvram SystemAudioVolume="％00"

 

[Jas-Singh685]

So I was just about to update this, well... kind of anyway.

Lauch the terminal：

step 1. sudo nvram StartupMute=%01
step 2. sudo nvram SystemAudioVolume="％80" or sudo nvram SystemAudioVolume="％00"

Thanks for this, the first command worked in itself, and the chime is now muted. I did have a look in Big Sur, and the "boot up sound" was unchecked after running the above command, and enabling the option in that OS again, removed the startupmute parameter in nvram -p. So it is definitely linked to that.

Interestingly, my T2 BridgeOS ROM version also got updated, to the Big Sur version as discovered here. https://mrmacintosh.com/category/bridgeos-ibridge/

Anyone with the same behaviour, I would imagine they have also been updated to this same version. And from what I hear, attempting to downgrade this is a big nope!

I can only assume that this is causing the chime to have this new behaviour, and why NVRAM resets don't mute the chime, as the new default is Big Sur, which is now enabled by default. I still can't figure out why I can't control the damn volume though! But at least it's muted for now, no more heart attack boots at night.

Running silent knight confirms the update. Both my iBridge and EFI versions exceed that is expected, Big Sur must have updated them!

 

[iMacDragon]

Every single mac os update/beta nowadays updates efi/t2 firmware, in my experience.

 

[Jas-Singh685]

Yeah that makes sense. It's the only logical explanation to the new behaviour of the default chime. Hopefully a further update will provide a volume control from the OS like before.