How does the Mac shut down the boot sound completely?

Mac users know that every time the boot, there will be a very special boot sound, sometimes louder, but also startled. If you want to temporarily prohibit this boot start tone, there is a simple way is to turn on the keyboard to hold down the mute button (F10), but this method is a symptom not a cure.

Workaround:

Open application, open utility, locate and open the Terminal program, and enter the following command and return (note that you do not copy more spaces when copying):

sudo nvram systemaudiovolume=%80

Then you will be prompted to enter the password, input your user password, enter the following figure. This will then be completely mute when you start the Mac again.

(Note: The input password is not visible, unlike the normal input password that can be seen, you just lose on it, enter the finished press RETURN.) )

If you want to restore a normal boot sound, just enter the following command again in the terminal:

sudo nvram-d systemaudiovolume

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