This past week, the Collaboratory housed A(n Underground) Tale of Two Cities, an installation that simulated subway sounds and images from Beijing and New York City. In that vein, Roman Mars’ “tiny radio show about design,” 99% Invisible, released a podcast four years ago about the sounds from the DC Metro system. Press play below to hear the ways in which noisy escalators can be likened to, among other things, whales mating and saxophones.