Acoustic black holes (ABHs) have shown extensive applications in vibration reduction and noise suppression. In the last decades, several types of ABHs, including circular and annular ABHs, have been used for vibration attenuation. However, only the circular ABH has been studied for sound radiation. In this paper, we have thoroughly compared the radiation damage of the two types of ABHs and presented the reduction mechanism. Moreover, both the sound radiation into the free half space and into the cavity has been studied. The former is achieved by developing the impedance matrix method, together with the supersonic intensity to unveil the mechanism of sound radiation reduction. The latter is managed by the mid-high frequency statistic modal energy distribution analysis (SmEdA) method to fast predict the response of the coupling plate-cavity system which is very tough with a deterministic method. Both methods are based on the Gaussian expansion method (GEM) which is very accurate to reproduce the vibration fields and modes of the plate with embedded different ABHs, via decompose the displacement with Gaussian basis functions in the framework of Rayleigh-Ritz method. Results show that the annular ABH has better sound mitigation performances than the traditional circular ABH, with the mechanism of better damping performance and the damage of radiation efficiency in subsonic region.

Annular acoustic black holes,Noise mitigation,Vibroacoustics,Gaussian expansion method,Statistical modal energy distribution analysis