Numerical simulation and experimental study of a broadband acoustic metamaterial duct muffler considering thermal-viscous loss

In this paper, a sub-wavelength sector acoustic metamaterial (SAM) cell was presented for duct noise attenuation. A numerical model considering thermal-viscous loss was established to quantitatively reveal the influence of different structure parameters on the effective bandwidth and peak frequency. Findings clarify that thermal dissipation occurs mainly in the cavity and viscous dissipation exists mainly in the channel. The negative effective bulk modulus for SAM was calculated by the parametric retrieving method. A developed sector acoustic metamaterial (DSAM) structure was proposed by periodically configuring the SAM. The corresponding numerical model was established, and the effective bandwidth of DSAM was calculated. Results demonstrate that the DSAM has sufficient bandwidth to ensure noise attenuation. The experiments were conducted using the quadrupole method acoustic test system under dual-load conditions. The error of the STL curve peak frequency for the SAM cell compared with the numerical calculation was 0.51 %, and the error of the effective bandwidth was 1.4 %, which verified the accuracy of the numerical model. This study serves as an essential catalyst for applying acoustic metamaterial in the field of duct noise attenuation.