Here is a new startup, Howloud, taking on the challenge of calculating and mapping residential noise levels. If you live in LA or Orange Counties, enter your address to see your Soundscore.
I noticed that the areas of Santa Clarita, Lancaster and Palmdale have not been calculated yet. Donate to their Kickstarter to get them done! Their plans are to build a sound map for North America, including mapping noise around buildings in 3D.