Investigating sound insulation performance of gradient airflow resistivity porous materials

The sound insulation performance of porous materials with gradient airflow resistivity is investigated using a combined approach based on the Johnson-Champoux-Allard (JCA) model and the Virtual Transmission Loss (VTL) method. These materials, known for their tunable acoustic absorption properties, are evaluated through finite element simulations and Statistical Energy Analysis (SEA) to assess the influence of resistivity distribution and layer configuration. Results show that a low-to-high rsesistivity gradient structure provides improved sound insulation characteristics, particularly when implemented as a three-layer design. Compared to uniform and high-to-low configurations, the optimized gradient structure achieves a higher transmission loss (TL) across the 1000–8000 Hz frequency range. Application to automotive acoustic packages demonstrates its practical effectiveness, with an increase in TL of up to 5.8 dB for the roof assembly, corresponding to a 5.8 dB reduction in the receiver sound pressure level (SPL). In contrast, the effectiveness of the gradient design for the dash was negligible due to its more complex structural constraints. This study underscores the importance of gradient structures in porous materials, demonstrating that significant improvements in TL can be achieved by adjusting the airflow resistivity gradient and layer structure, particularly in automotive interior acoustics.