For Mac systems with Magsafe adapters, wall power status has mostly been identifiable by simply looking at your power adapter connector. In doing so, an indicator light of orange or green will tell you both that you are receiving power, and that you are either charging or are fully charged. There is no default sound to indicate attachment to wall power; however, if you have OS X Yosemite installed and are keeping your system up to date, then you have the option to enable one.

As discovered recently by the French tech site MacG, the latest OS X 10.10.3 update includes a service to provide an audio notification when attached to power. The service comes by way of a small app called PowerChime in the System’s CoreServices directory (/System/Library/CoreServices), and can be enabled by running the following command on a MacBook that has a MagSafe power adapter:

To enable this service, first open the Terminal utility and run the following command:

defaults write com.apple.PowerChime ChimeOnAllHardware -bool true

Now go to the Macintosh HD > System > Library > CoreServices folder and open the PowerChime.app file. It will launch but not show any windows or other visual elements.

When done, your Mac should now sound the small chime notice when you attach your power adapter, putting it in line with the behavior of various iOS devices, so if you own an iPad or iPhone, then you will recognize the sound immediately. If after rebooting or logging out and logging back into your Mac, the indicator sound does not play when power is attached, then go to the Users & Groups system preferences, select your account and choose Login Items, and then add the app to the list of login items for your account.

While fun, this feature does not provide much utility to OS X, especially given the immediate visual feedback of the power adapter’s status lights. In addition, there is no sound played for an interruption in AC power, which may be the more useful to notify you a change to the power state has been detected.

One unfortunate aspect of this chime, however, is that it will sound even if you have your Mac’s volume muted, which may not be desired in all circumstances. If you find you would prefer having your Mac run without this sound, then you can temporarily quit the service by opening Activity Monitor (in the Applications > Utilities folder), searching for “PowerChime,” and quitting the program (it will re-launch when you next log in). You can also disable it by running the following command in the Terminal:

defaults delete com.apple.PowerChime ChimeOnAllHardware

Finally, if you added the PowerChime app to your login items, then be sure to remove it from this list to prevent it from launching, and you should be all set.