The acoustic streaming effects and transmission mechanisms of a micro-cavity acoustic black hole structure with an abrupt cross-section

This paper investigates the acoustic streaming effects (ASEs) and mechanisms behind the transmittance of sound in a metallic micro-cavity acoustic black hole (ABH) structure with an abrupt cross-section and examines the sound field flow characteristics inside the micro-cavity ABH under the sound excitation, such as the velocity, acceleration and pressure fields. And the sound transmission mechanisms are characterized by the ASEs which can be obtained by solving Navier-Stokes equations. The numerical results show that the sharp increase in the velocity and acceleration at the ABH tip position is the main reason for the focusing of the sound energy. And the dramatic increase in the tip cross-section reduces the acoustic streaming velocity, which is the main reason for the attenuation of the sound energy. Additionally, the thermoviscous effect of the acoustic boundary layer can also dissipate the low-frequency sound energy. The sound insulation experiment shows that the proposed micro-cavity ABH structure has a sound transmission loss (STL) of over 15dB in the low-frequency regime. This research reveals the mechanisms of the ASE's work on the sound transmission properties of the micro-cavity ABH and provides new insight into low-frequency sound wave suppression. The ABH structure proposed in this paper has excellent strength, bearing capacity and long lifecycle, so it can be applied in the construction industry through its integrated design of structure and performance.

Automated summary

This paper investigates the effects of acoustic streaming and mechanisms of sound transmission in a metallic micro-cavity acoustic black hole (ABH) structure. The study examines the sound field flow characteristics inside the micro-cavity ABH under sound excitation and characterizes the sound transmission mechanisms using obtained acoustic streaming effects. The numerical results show that the increase in velocity and acceleration at the ABH tip position is the main reason for sound energy focusing, while the dramatic increase in the tip cross-section reduces the acoustic streaming velocity, resulting in sound energy attenuation. The thermoviscous effect of the acoustic boundary layer also dissipates low-frequency sound energy. The proposed micro-cavity ABH structure demonstrates sound transmission loss in the low-frequency regime, making it suitable for applications in the construction industry.