Listener Ryan heard an eerie noise while crossing the Golden Gate Bridge on his motorcycle. He's not the only one -- the sound can be heard from miles away. What's going on?

Additional Reading:

Reported by Rob Speight with support from Gabe Meline. Bay Curious is made by Olivia Allen-Price, Katrina Schwartz and Rob Speight. Additional support from Erika Aguilar, Jessica Placzek, Kyana Moghadam, Paul Lancour, Suzie Racho, Carly Severn, Bianca Hernandez, Ethan Lindsey, Vinnee Tong and Don Clyde.