UPDATE, 1:30pm: The sound is intentional. See below.
If you are anywhere in the vicinity of the Golden Gate Bridge right now, you are probably asking yourself: What in the world is that sound? A long, loud hum from a deep sea creature? Alien frequencies from outer space? An enormous sigh from San Francisco's greatest landmark, finally registering its dismay at the state of the world?
Nope—the eerie sound you're hearing from the Golden Gate Bridge is in fact the result of new sidewalk railing slats, just installed, meant to better handle the wind. Funny thing about wind: when it passes through certain open spaces, it creates a hum. This is how all reed instruments work, and because it spans a very windy gap across the Bay, the Golden Gate Bridge is now effectively a giant orange wheezing kazoo.