Found this here
Two scripts, both saved in /usr/bin:
loginscript #!/bin/bash /usr/bin/osascript -e 'set volume without output muted'
logoutscript #!/bin/bash /usr/bin/osascript -e 'set volume with output muted'
Make them executable:
sudo chmod a+x /usr/local/bin/loginscript sudo chmod a+x /usr/local/bin/logoutscript
Then set them to be called at boot/shutdown:
sudo defaults write com.apple.loginwindow LoginHook /usr/local/bin/loginscript sudo defaults write com.apple.loginwindow LogoutHook /usr/local/bin/logoutscript
And if you want to remove them:
sudo defaults delete com.apple.loginwindow LoginHook sudo defaults delete com.apple.loginwindow LogoutHook sudo rm /usr/local/bin/loginscript sudo rm /usr/local/bin/logoutscript