Why Do S.F.'s Crosswalks Play a Machine Gun Sound? And How Do Architects Design for Sound?

<p>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.</p><p>Additional Reading:</p><p>An Architect Who Listens To Buildings</p><p>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...