Ultrabroadband sound control with deep-subwavelength plasmacoustic metalayers

Controlling audible sound requires inherently broadband and subwavelength acoustic solutions, which are to date, crucially missing. This includes current noise absorption methods, such as porous materials or acoustic resonators, which are typically inefficient below 1kHz, or fundamentally narrowband. Here, we solve this vexing issue by introducing the concept of plasmacoustic metalayers. We demonstrate that the dynamics of small layers of air plasma can be controlled to interact with sound in an ultrabroadband way and over deep-subwavelength distances. Exploiting the unique physics of plasmacoustic metalayers, we experimentally demonstrate perfect sound absorption and tunable acoustic reflection over two frequency decades, from several Hz to the kHz range, with transparent plasma layers of thicknesses down to lambda/1000. Such bandwidth and compactness are required in a variety of applications, including noise control, audio-engineering, room acoustics, imaging and metamaterial design.

Automated summary

Controlling audible sound requires broadband and subwavelength acoustic solutions, which are currently not available. This paper introduces the concept of plasmacoustic metalayers to solve this problem, demonstrating that small layers of air plasma can interact with sound in an ultrabroadband manner over deep-subwavelength distances. By exploiting the unique physics of plasmacoustic metalayers, perfect sound absorption and tunable acoustic reflection can be achieved over a wide frequency range, from several Hz to the kHz range, using transparent plasma layers with thicknesses down to lambda/1000. This bandwidth and compactness are essential for various applications including noise control, audio engineering, room acoustics, imaging, and metamaterial design.