I don’t know about you guys but I have always felt annoyed with the Mac startup chime every time I turn on my mac. Coming from a windows background, I am never used to the startup sound and always found it weird to listen to it every single time.
This will remind you of the annoying sound I am talking about:
Why the startup chime?
I always wondered whats the purpose of this chime, thought I should share that aswell:
The sound indicates that diagnostic tests run immediately at startup have found no hardware or fundamental software problems. – Wikipedia
The Fix:
I usually prefer using ear phone with my Macbook and I discovered this feature that sound volumes are managed individually by OSX. Here is what you do:
- Unplug any ear phones or output devices if there are connected any. Wait for a couple seconds, maybe 5, making sure OSX detects the unplug.
- Click on the volume control and bring the level to least bottom making the output mute.
- Then plug in the ear phones and wait for a couple seconds for OSX to detect. Then adjust the volume control the same way as you want.
Now when you unplug the ear phones and shut down the Mac it will be on mute and when you start up there will be no start up sound since you shut down the Mac on mute.
Hope this simple trick worked well for you. 
Alternatively, just hold down the mute key on the keyboard during start up.
yes but you dont always remember to hold down the key on startup