How to turn off or mute a Mac's boot sound chime?

Hello guys,

I already searched and there are a few threads on this but most of them are pretty old (2008-ish) and those techniques do not apply anymore.

To keep this short: Can I mute, turn off, volume down the chime boot sound that a Mac does when it boots up? I understand that the sound is useful as it is a diagnostic that everything is OK but i find it too loud and annoying.

I am looking to upgrade today from Yosemite to El Captain and was asking for those who already updated if Apple included a function or if you know anything that might work.

I have heard that there are some script/string to enter in the terminal but no longer work and that I could mute the mac before shutting down which seems very primitive.

Thank you!