Perplexed Bay Area residents have reported hearing an ominous ringing noise emanating from the Golden Gate Bridge, which can be heard in videos taken miles away.

“Can someone explain me why is this eerie sound has been going on for an hour in #SanFrancisco #presidio #sound #eerie #whatisthis “ one Twitter user wrote.

As part of the wind retrofit project, a length of the west side bicycle path railings have been modified with thinner slats to reduce wind resistance. The engineers identified the potential sound problem during wind tunnel tests but decided it would not be a common occurrence, however recent windy weather has amplified this new sonic feature of the Golden Gate Bridge.

See also The Windsor Hum