Golden Gate Bridge’s Mysterious Humming Sound Explained

San Francisco's Golden Gate Bridge has long been something tourists flock to see. But now it's something people in the area can also hear — on a windy day, the landmark bridge actually emits a humming sound, puzzling and irritating many people who live as far as four miles away. It's all part of a new project on the 83-year-old bridge that makes it more aerodynamic. Handrail supports have been replaced with thinner vertical slats that whistle when high winds pass through them.