Controlling the Spatiotemporal Response of Transient Reverberating Sound

Abstract

Sound propagating inside a room is multiply scattered by the boundaries and other obstacles, forming a complex reverberating sound field (RSF). Such RSFs are not only spatially disordered but also temporally scrambled. Although the spatial control of steady-state RSFs at single frequencies is successfully achieved by extending the idea of wavefront shaping to acoustics, time-coherent polychromatic control of RSFs has remained out of reach. Here, we report spatiotemporal acoustic wavefield shaping by adaptively reshaping acoustic impulse responses at arbitrary positions and different instants in a reverberating room using spatial sound modulators---a reconfigurable and programmable membrane-type acoustic metasurface capable of encoding desirable phase factors over a finite bandwidth. We further analyze the mechanism and performance of spatiotemporal wavefield shaping with a simple numerical model derived from multiple scattering in the time domain. Our results expand the capabilities of RSF control to the temporal domain and demonstrate the possibilities for transient engineering of polychromatic sound in acoustic communication, imaging, and holography.