Broadening efficient sound absorption bandwidth of spatial bending acoustic metasurfaces with multi-parameter variation

Abstract Due to limitations in the space for the installation of noise reduction structures in some engineering application fields, broadband efficient noise reduction has always been a key issue in academic and engineering fields. Faced with this issue, in this work, a deep-subwavelength acoustic metasurface with embedded necks and bending channels is proposed. Firstly, theoretical models for the sound absorption coefficient of traditional Helmholtz resonators(THRs), embedded Helmholtz resonators(EHRs), and spatial bending acoustic metasurfaces (SBAMs) with a thickness of 12 mm were established using the thermal-viscous model, end acoustic radiation correction theory, and transfer matrix method, which prove that the SBAM unit has deep-subwavelength characteristics. Subsequently, adopting theoretical models and the complex frequency plane method, the SBAM unit with a side length of 50 mm and a thickness of 12 mm was designed, which exhibited perfect absorption at 541 Hz. The perfect absorption mechanism was elucidated through simulations. Theoretical and simulation models were used to analyze the regulation law of different geometric parameters on the acoustic performance for ultra-thin SBAM units. The results indicate that by accurately tuning multiple geometric parameters, ultrathin and perfect-absorption SBAM units with a thickness of 12 mm in the broadband range of 463–672 Hz can be achieved. Furthermore, it was experimentally studied how the equivalent length L influences the sound absorption performance of SBAM units, and the correctness of the theoretical and simulation results was verified. These results will provide a theoretical reference and engineering application for broadening the low-frequency noise reduction frequency band in compact spaces, improving the spatial utilization of sound absorption structures, and achieving broadband noise control at low and medium frequencies.