Design of adjustable low-frequency sound absorbers through hybrid digital-analog shunt loudspeakers

Low frequency noise is the primary frequency range that affects individuals’ physical and emotional well-being. The impact of conventional low-frequency sound absorption technologies is restricted by spatial constraints. The shunt loudspeaker is an emerging technology for controlling low-frequency noise, where the acoustic impedance can be modified by a shunt circuit. However, the imprecision and instability caused by the nonlinear impact of loudspeakers and the parasitic resistance of electronic components in analog circuits is challenging. To overcome the problem, this research proposes an adjustable low-frequency sound absorber based on a hybrid digital-analog shunt loudspeaker. The equivalent circuit model is initially formulated, and the design of the adjustable synthetic impedance is then developed. Simulations and experiments are conducted to validate the theoretical model. The proposed absorber demonstrates excellent capabilities in absorbing low-frequency sound with greater precision, stability, independent of the cavity depth and ease of adjustment, enabling a wide range of practical applications.