Laboratoire d'Acoustique de l'Université du Mans (LAUM), UMR 6613, Institut d'Acoustique - Graduate School (IA-GS), CNRS, Le Mans Université, Le Mans, France.
Nat Commun. 2023 Jul 7;14(1):4028. doi: 10.1038/s41467-023-39727-4.
The absorption of airborne sound is still a subject of active research, and even more since the emergence of acoustic metamaterials. Although being subwavelength, the screen barriers developed so far cannot absorb more than 50% of an incident wave at very low frequencies (<100 Hz). Here, we explore the design of a subwavelength and broadband absorbing screen based on thermoacoustic energy conversion. The system consists of a porous layer kept at room temperature on one side while the other side is cooled down to a very low temperature using liquid nitrogen. At the absorbing screen, the sound wave experiences both a pressure jump caused by viscous drag, and a velocity jump caused by thermoacoustic energy conversion breaking reciprocity and allowing a one-sided absorption up to 95 % even in the infrasound regime. By overcoming the ordinary low frequency absorption limit, thermoacoustic effects open the door to the design of innovative devices.
空气中声音的吸收仍然是一个活跃的研究课题，尤其是在声学超材料出现之后。尽管屏幕障碍已经亚波长化，但迄今为止开发的屏幕障碍在非常低的频率（<100Hz）下不能吸收超过 50%的入射波。在这里，我们探索了基于热声能量转换的亚波长和宽带吸收屏幕的设计。该系统由一侧保持室温的多孔层组成，而另一侧使用液氮冷却至极低温度。在吸收屏幕处，声波不仅经历由粘性阻力引起的压力跳跃，还经历由热声能量转换引起的速度跳跃，这种能量转换破坏了互易性，允许单向吸收高达 95%，即使在次声范围内也是如此。通过克服普通的低频吸收限制，热声效应为设计创新设备开辟了道路。
