Can I change the startup sound on macOS Big Sur?
On an Intel Mac, the startup chime is part of the Mac's firmware. You can't just replace it, like you could a normal audio file.
Think about this logically—the startup chime plays as soon as you turn on your computer, before it loads the operating system. And if you wipe your hard drive, the sound will still play. How would that be possible, if the chime was stored on your drive?
On Intel Macs with T2 chip, the startup sound is stored in there. You can change the sound by jailbreaking it with Checkra1n. 0. You will need another Mac or Linux PC.
- Jailbreak the T2 with Checkra1n.
- Connect to it with SSH.
- Convert the startup sound file to aiff.
- Replace /System/Library/PrivateFrameworks/BridgeAccessibilitySupport.framework/AXEFIAudio_VoiceOver_Boot.aiff with that file. (Back up the original file before doing.)
- Use the ‘snappy’ command to make the change permanent.
For more information, please refer to https://checkm8.info/blog/customize-macos-boot