I am still on Catalina 10.15.7 and just did the latest security and Safari updates today. I would post the versions, but not sure where to look for them. Anyhow, now on boot up I get the Apple startup chime which I do not like. I've read that apple put in back with Big Sur - but I don't have that. Can someone tell me how to disable the startup chime? Some people online are saying that there should be an option in Sound Preferences but I don't see that either. I'm guessing I can mute, but I only want to disable the startup sound not all sounds.
This is pretty easy. In fact there are articles out there that describe how to do this.
Briefly, open terminal app in /Applications/Utilities and paste in this command
sudo nvram StartupMute=%01
It will ask for your password and then just return to the terminal prompt. When you reboot the chime will be gone.
Note that if you reset NVRAM (some old farts like me still call it PRAM) the chime will return, you just have to do that command again.
to turn the chime on
sudo nvram StartupMute=%00
In case you change your mind...
All commands to be entered in Terminal followed by Enter/Return. I recommend copy/paste.
sudo command may prompt for your login password. Enter it as you would the login screen. It will not appear in Terminal as you type.
Try this first
sudo nvram SystemAudioVolume=%80
If that doesn't work, you can try these variations:
sudo nvram SystemAudioVolume=%01
sudo nvram SystemAudioVolume=%00
sudo nvram SystemAudioVolume=' '
To get the sound back or if something goes wrong…
If you change your mind, enter this:
sudo nvram -d SystemAudioVolume