Our cities are increasingly acoustic cities. The most immense or most intimate public spaces are stages on which sound is one of the actors. John Bingham-Hall is the director of Theatrum Mundi, which was founded by the great sociologist and urbanist Richard Sennett. He works with Gascia Ouzounian, co-director of Recomposing the City, on the Acoustic Cities project. In this Metropolitan section, they talk about their work and the basic topics of sonic urbanism, including sonic citizenship, sonic archaeology and ‘sonic justice as a right to access to quiet or indeed to make noise’. A new way of hearing the city that underlies a new way of seeing the city.