Chromebooks added a charging sound, but you have to manually enable

There are officially three charging sounds: 

When your battery is above 80%: G major chord on piano from Pixel devices “but with more low frequency content to take advantage of the robust bass sound that the larger speakers on a ChromeOS device support” + white noise-inspired sparkle dust “to add a tactile quality — as if it’s some kind of naturally occurring sound”

79-16%: “a variation on the charging sound, which includes an additional element that’s almost like a cheerful ‘swoop,’ at the start of the sound, indicating that the battery is kind of at a medium level”

Under 15%: “includes a similar additional swooping sound at the start, but it’s slightly higher-pitched and more noticeable”

In terms of actually implementing in ChromeOS:

The team decided to use FLAC, an open-source format which maintains the original quality of the audio while still allowing the file to be shrunk down to a smaller size — which meant the team also needed to expand the existing audio capabilities in ChromeOS to support playing the new FLAC format, ensuring that the new sound would work on different devices, no matter the hardware.

Google says these audio cues “aid in accessibility for blind and low-vision users by making it easier to ascertain relative battery life without needing to check with a screen reader first.” Another consideration was how Chromebooks are used in schools so the team made sure the “sound and volume were helpful and not distracting.”

With this framework in place, “ChromeOS is ready for any additional sounds the team may want to add down the line.”