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.

Development of Adjustable Parallel Helmholtz Acoustic Metamaterial for Broad Low-Frequency Sound Absorption Band

“…The proposed adjustable parallel Helmholtz acoustic metamaterial (abbreviated as the APH-AM) was developed by introducing the multiple resonant chambers and tuning the length of rear cavity for each chamber. It should be noted that the tuning mechanism required manual mechanical intervention and it was not an automatic process, which was quite different from the electronically programmable metasurfaces [ 30 , 31 , 32 , 33 , 34 , 35 ]. The sound field minimization through in situ engineered destructive interferences could maximize/minimize the sound field inside a room at a desired point for a static single-frequency [ 30 ], a static multi-frequency or a transient multi-frequency field [ 31 ], which could achieve ultrabroadband absorber in microwave domain [ 33 ].…”

Experimentally realized physical-model-based frugal wave control in metasurface-programmable complex media

“…Currently the most prominent example are metasurface-programmable smart radio environments, foreseen to play a pivotal role in next-generation wireless networks 1 – 3 . The same concept also underlies promising implementations of reconfigurable holographic antennas 4 – 6 and wave-based signal processors 7 , 8 in the microwave regime, and emerges in nanophotonics 9 – 11 , optics 12 – 14 and room acoustics 15 , 16 , too. However, the inverse-design problem of identifying a configuration of the DOFs that yields a desired system transfer function is notoriously difficult for two reasons.…”

RIS-Based Radio Localization in Rich Scattering Environments: Harnessing Multi-Path with ANN Decoders

“…In fact, MPCMs emerge yet more generally across scales and wave phenomena as new approach to controlling wave-matter interactions besides the established approaches of metamaterial engineering (i.e., designing the entire system from scratch) and wavefront shaping (i.e., designing the impinging wavefront). Some experiments were already reported in nanophotonics [14,15,16], optics [17,18,19] and room-acoustics [20,21]. Therefore, many of the tools discussed in this chapter may soon play a role not only in next-generation wireless networks but more generally in the broader field of MPCMs.…”

“…To this end, we apply multiple linear regression to the measured data in order to identify the best possible linear model; the accuracy of the latter is an upper bound to the accuracy that could be achieved with the linear cascaded model from Eq. (21). For a given wireless channel 𝐻 𝑖 𝑗 (c), and the corresponding prediction based on the linear model H𝑖 𝑗 (c), we evaluate…”