Adjust the Mac Startup Volume, Even If Your Speakers Are Plugged Into a Power Outlet
The Mac startup volume is linked to the output volume of the internal speakers. Simply mute it completely , but given that this signal is for troubleshooting purposes , it is usually best to leave it on . In any case, if you have speakers connected to you, this tone seems to do whatever it wants to do. Here’s how to fix it.
It turns out that you can’t adjust the volume of your Mac’s internal speakers when external speakers are connected to them. This way, no matter what volume level your desktop speaker is set to, these internal speakers will do whatever they want, so the startup beep will not match your normal volume. Correction? Turn off your speakers, then go to System Preferences> Sound> Output. You should see the internal speakers set as an output device. Come on, turn down the volume here. On the next reboot, it will be as quiet (or loud) as you like. Likewise, while you are there, you can adjust the volume depending on the other output devices if you use many others .
Tip: adjust the startup sound volume | Six colors