Why Do S.F.'s Crosswalks Play a Machine Gun Sound?

The crosswalks in San Francisco, and many other Bay Area towns, play a 'machine gun' sound when the 'walk' sign is illuminated for pedestrians. A Bay Curious listener recalls hearing chirping sounds in other areas. Why do ours sound the way they do? Plus, we get to know an architect who listens to buildings.

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An Architect Who Listens To Buildings

Reported by Olivia Allen-Price, Annika Cline and Sam Harnett. Bay Curious is made by Olivia Allen-Price, Jessica Placzek, Katie McMurran and Rob Speight. Additional support from Julie Caine, Paul Lancour, Kyana Moghadam, Suzie Racho, Ethan Lindsey and Patricia Yollin.