My Mac (which is running OS X Mavericks) makes a deafening noise when it starts up, even if headphones are plugged in. How can I mute it? And why is it bypassing the headphones? Normally having them plugged in mutes the speakers automatically.

Covering ears - How to mute Mac startup sounds

Turn it down! (Cropped) photo by oddharmonic, used with permission under terms of Creative Commons Licence

We hear this query a lot, and it’s an annoying one - particularly for mild-mannered office workers. You sit at your desk all day listening to music on your headphones, then switch off the Mac at the end of the day. Then when you come in next mooring and switch the Mac on, it blares out the startup chime through the speakers and ignores the headphones.

This is particularly galling if you’re a little late in the office and want to keep things on the down-low.

The solution is actually very straightforward, although the cause is interestingly complicated. If you just want to fix the problem, skip down to the solution at the end.

Read our OS X Mavericks tips and tricks, get more out of Mac OS X 10.9 Mavericks feature to uncover the best new features in Mavericks.

How to mute Mac startup sounds: The cause

Why does the Mac ignore the headphones when it blares out the startup sound? The output source for startup chimes are always the external speaker. Until the software that controls the selection of headphone or speakers comes online, the Mac simply defaults to the speaker.

The volume control is also software-based and therefore can’t function while the Mac is waking up - so hitting the mute or volume down buttons when the Mac is starting up (or even off - obviously) won’t help.

However, the Mac can remember volume settings between one session and another.

How to mute Mac startup sounds: The solution

Hit the mute button (there’s one on the standard Apple keyboard - most likely F10) before you switch off the Mac at the end of the day. It will remember this setting when it next starts up and won’t make a peep.

Easy!