Beautiful background images and videos have been part of Bing’s homepage for a while, but now Microsoft has added optional audio to their Bing home page videos. Bing blogs explains the new feature including how to get the audio to play.
The example they use is today’s Bing homepage which features geese from the Sacramento National Wildlife Refuge taking off over a swamp. In the lower right hand corner of the screen there are multiple buttons, including a new set of sound bars bouncing up and down. If you click that button the audio begins, in this case geese noises. You can also play or pause the video. If you hover over the info button to make it expand you'll be taken to Bing's "Backstage", where you'll see more information and be able to click through different homepage photos.