Compact multifunctional slit-type Helmholtz silencer for broadband sound attenuation with ventilation

Achieving efficient broadband sound attenuation at low frequencies without obstructing airflow remains a major challenge in duct acoustics and ventilated noise-control systems, due to the inherent trade-off between acoustic performance and airflow capacity. In this study, we present a compact, multifunctional slit-type acoustic silencer (MSAS) that integrates concentric slit-type Helmholtz resonators (SHRs) within a subwavelength structure while maintaining 36% open area to support high ventilation. A simplified analytical model is developed to evaluate the silencer's acoustic performance, capturing both absorption and transmission loss (TL). By embedding the complex acoustic impedance of core SHRs into a transfer matrix framework and accounting for their interactions with peripheral SHRs, we exploit coherent coupling between weak resonances to achieve a pronounced broadband attenuation effect. Simulations predict absorption greater than 80% and TL above 15 dB across the 0.7–0.9 kHz range, with experimental results from a fabricated four-unit prototype closely matching these predictions. The proposed MSAS design delivers an effective subwavelength solution for applications requiring simultaneous noise reduction and ventilation, such as office partitions with ventilation, ducts, and acoustic barriers.