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低频声学全吸收点——解决低频噪音的一种有效方法

Low frequency acoustic sinks

  • 摘要: 低频噪音以其超强的穿透力和难以吸收的特性成为一个令人烦恼的工程技术难题。作者在最近的研究工作中发现的低频声学全吸收点是解决低频噪音问题的一种有效方法,即经过一些简单的设计,原本声学上的全反射表面可以借助于一种特别的表面杂化共振实现对空气中声音的阻抗匹配,从而在一些可调的特定频率不产生反射。与此同时,由于也不存在任何透射,声音在这样的表面要么全部被耗散吸收,要么转化为其他形式的能量,比如电流。在实验中,这样的“声—电”能量的转化效率可以高达23%。需要特别指出的是,在这种被设计了亚波长结构的表面(又称“超表面”)上,每一个吸收单元对于声波都如同尺寸可以忽略的“点”,这样的特性不论是在实际应用还是理论上(比如时间反演声学)都有着非常重要的意义。文章介绍了这种低频声学全吸收点的原理和实现方法。

     

    Abstract: An impedance-matched surface has the property that an incident wave generates no reflection. Here we demonstrate that, by using a simple construction, an acoustically reflecting surface can acquire hybrid resonances and become impedance-matched to airborne sound at tunable frequencies, such that no reflection is generated. As there can be no transmission, the impedance-matched acoustic wave is hence either completely absorbed at one or multiple frequencies,or converted into other forms of energy, such as an electrical current. A high acoustic-electrical energy conversion efficiency of 23% has been achieved. Each resonant cell of the metasurface is deep-subwavelength in all its spatial dimensions. With its thickness less than the peak absorption wavelength by two orders of magnitude, the resonant cell itself can be treated as an acoustic sink, acting as a time-reversal counterpart for an acoustic point source.

     

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