Compact multi-resonator ventilated duct silencer with broadband sound attenuation and steady airflow

Abstract This research presents the design of a compact acoustic metamaterial duct silencer capable of attenuating a wide range of frequencies while allowing steady airflow. The proposed device incorporates a series of space-folded slit resonators, each exhibiting a different length tailored to attenuate a specific frequency. Combining these side-loaded resonators onto a host tube achieves broadband noise reduction thanks to the cumulative effects of the individual components and their synergistic interactions. Compared with many traditional duct silencers and mufflers, this design enables unobstructed flow through its central region, resulting in a much lower fluid pressure drop across the structure. Additionally, the use of space-folded resonators results in a significant reduction in the overall diameter of the device, leading to a high efficiency of volume usage. Theoretical calculations based on the transfer matrix method and numerical simulations using finite element analysis are used to validate the structure. Implementing a geometry generation function allows the structure to be parametrically optimized to suppress noise within given frequency ranges. Using these methods, a design is carried out that maximizes transmission loss (TL) from 650 Hz to 2000 Hz with the outer diameter of the structure constrained to 0.2 m. The cumulative effect of the tuned resonator slits results in an average measured TL of 36.3 dB within the target frequency range in the stationary scenario and 17.2 dB under grazing flow. The demonstrated utility of the silencer in achieving comprehensive noise control while maintaining low flow resistance makes it a promising candidate for various applications such as automotive exhaust systems, industrial machinery, and naval vessels. Our demonstration paves the way for the development of new duct silencers that can meet the growing demand for effective noise control in various settings where unrestricted fluid flow and broadband attenuation are paramount.