How to completely turn off the Apple Mac boot sound

How to completely turn off the Apple Mac boot sound

1, open "Application", open "utility", find and open the [terminal] program, and then enter the following command and return (note, copy the time do not copy more space):

sudo nvram systemaudiovolume=%80

Mac completely shut down boot sound tutorial

2, then 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.) )

3, if you want to restore the normal boot blunt, as long as in the terminal to enter the following command again:

sudo nvram-d systemaudiovolume