The chime, which usually means your Mac passed the startup diagnostic test, can be replaced by a sequence of audible tones that signal various hardware failures, including bad RAM or EFI ROM (Extensible Firmware Interface Read Only Memory).
The Chimes of Death
Over the years, the tones the Mac generates when the startup test fails became collectively known as the chimes of death. As scary as that sounds, Apple sometimes added a bit of humor to the chimes of death, as it did with the old Performa series of Macs, which used a car crash sound. There were also one or two PowerBook models that used a rendition of the Twilight Zone theme.
Adjust the Startup Chime Volume
Because the startup chime can provide troubleshooting clues, it’s not a good idea to disable it by muting the chime volume. However, there’s no reason for the chimes to be set so loud. The way to turn down the volume of the startup chime isn’t readily apparent, especially if you have external speakers, headphones, or other sound devices connected to your Mac. Nevertheless, the process is easy, if a bit convoluted. Before you start, do the following:
Remove any speakers or headphones connected to your Mac’s headphone/line-out jack.Disconnect any USB, FireWire, or Thunderbolt-based audio devices connected to your Mac.Disconnect any Bluetooth audio devices you may be using.
With all external audio devices disconnected from your Mac, you’re ready to adjust the startup chime’s volume level. That’s it. You’ve adjusted the startup chime volume, as well as any alert chimes that use the internal speakers. Because you removed the externally connected audio devices, you should see only a few output options, including Internal Speakers. Reconnect any external audio devices that you connected to your Mac.
Use Terminal to Mute the Startup Chime
There’s another method for controlling the startup chime volume. Using the Terminal app, you can mute any sound played through the internal speakers. This isn’t the best option; lowering the volume using the Sound preference pane is a better course of action. The advantage of the Terminal method is that it works with any version of macOS or OS X, while the simpler Sound preference pane option is a bit iffy in early versions of the OS.
Unmute the Startup Chime in Terminal
Should you ever want to unmute the startup chime and return it to its default volume, return to Terminal and enter the following command: sudo nvram –d SystemAudioVolume You’ll need to provide your administrator password to complete the process.
