Bandgap Mechanism of Phonon Crystals Coupled to Acoustic Black Holes

In this study, phonon crystal structures embedded in acoustic black holes are discussed. The low-frequency band gap is widened by exploiting the low-frequency, broadband and multimode properties of the acoustic black hole. The energy band properties of the acoustic crystal structure embedded in an acoustic black hole are calculated by means of a finite element method. The mechanism of band gap generation is investigated. The vibration transfer characteristics of finite period structures are analyzed. The influence of the structural parameters of the acoustic black hole is analyzed. The results show that the acoustic crystal structure embedded in an acoustic black hole has multiple band gaps in the 500 Hz band and the band gap coverage is increased to 45.18%. The starting bandgap is 16.10% lower than before embedding in the acoustic black hole and the width of the first bandgap expands to 173.03% of that before embedding in the acoustic black hole. The onset and termination frequencies of the first band gap are mainly determined by the vibrational modes of the scatterer and the acoustic black hole structure. The vibrational transfer of the finite period structure is analyzed and shows good damping characteristics in the bandgap interval. Finally, vibration experiments verify the vibration damping effect of the proposed coupled acoustic black hole phononic crystal, and the relevant findings of this paper can be used in the vibration damping design of plate structures, enriching the experience of research related to acoustic black holes.