In 2018, engineers installed vertical slats along the railing of the Golden Gate Bridge in San Francisco. This had a surprising effect: Wind blowing through the slats causes the air around them to vibrate, producing sound waves.
Humming Bridge
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GIANT HARMONICA?
When wind blows through the slats on the Golden Gate Bridge, it creates a sound people can hear miles away.
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Depending on wind speed, residents of the city can hear two distinct hums: one high-pitched, and one low. Some say it sounds like beautiful music. For others, the constant noise is torture. “We want to be good neighbors,” says Paolo Cosulich-Schwartz, spokesperson for the bridge, so engineers set out to put a stop to the sound.
After testing a full-size model of the bridge’s railing in a massive wind tunnel, they came up with a solution: two U-shaped clips and a rubber sleeve, applied to each of the 12,000 slats. The project—which is set to be completed by the end of 2022—will minimize air vibrations, stopping the hum.
HOW SOUND WAVES WORK
When an object vibrates, the air around it vibrates as well. These vibrations travel through the air as sound waves. Think about the two distinct tones created by the vibrating bridge—how would those sound waves look similar? How would they look different?
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