Fig. 2: Active control of the plasmacoustic sources.
From: Ultrabroadband sound control with deep-subwavelength plasmacoustic metalayers
a A microphone is used to create a feedback loop between the front acoustic pressure and the voltage driving the plasmacoustic metalayer. Due to the deep subwavelength distance separating the electrodes, we assume that the monopolar and dipolar plasmacoustic sources are punctual and both located at the origin. The microphone measures the total pressure pt at position − x0. The acoustic medium is terminated by a boundary with general acoustic impedance Zl. b Bode plot of the control transfer function from the total pressure pt to the applied AC voltage uAC to target full sound absorption.
