How to disable boot chime in Yosemite?

Question

Hi everyone,
I'm trying to disable the boot chime in Yosemite. Previously I was able to do this by way of a terminal command (sudo nvram SystemAudioVolume=%80) but this doesn't seem to work in Yosemite.
I know why the boot chime is useful and why I should just mute my speakers before shutting down, but I just want it disabled once and for all.
Besides the use of 3rd party apps, is there any way to disable it?
Thanks for any input.

Answer 1

This worked in Mavericks 10.9.5.
I had this scrapped from someone else's post.
Basically what it does is when you log off, it mutes the volume. On log-on, it un-mutes so your normal volume returns.
-Create scriptfile for muting:
sudo nano /opt/local/bin/mute-on.sh
#!/bin/bash
osascript -e 'set volume with output muted'
-Create scriptfile for unmuting
sudo nano /opt/local/bin/mute-off.sh
#!/bin/bash
osascript -e ‘set volume without output muted’
-Make both files executable:
sudo chmod +x /opt/local/bin/mute-*
-Check if any hooks already exist (these will be overwritten, so make sure it is OK for you)
sudo defaults read com.apple.loginwindow LoginHook
sudo defaults read com.apple.loginwindow LogoutHook
-Add hooks for muting
sudo defaults write com.apple.loginwindow LogoutHook /opt/local/bin/mute-on.sh
sudo defaults write com.apple.loginwindow LoginHook /opt/local/bin/mute-off.sh
–to delete the hooks, use the following:
sudo defaults delete com.apple.loginwindow LoginHook
sudo defaults delete com.apple.loginwindow LogoutHook
-Note that script files must be owned by root.
I wish Apple starts rethinking these unneeded clutters that really annoys new mac users.