New theoretical model for drumlike silencer

A new technique called drumlike silencer was used to reduce sound propagations in ducts. However, the corresponding theoretical model is only valid for a plane wave in ducts without flow. A general model for describing the effect of the drumlike silencer in ducts based on generalized Lighthill equation and Green's function theory was put forward. Compared to the existing work, the present model includes the effect of flow Mach number, higher order modes and duct structure parameters on the sound propagation. The relevant numerical results show that the control of higher order modes in a flow duct will be much more difficult than that of plane waves. Therefore, how to carefully make use of drumlike silencer to suppress the sound propagation with more complicated noise sources is worthy to be further investigated. It is also believed the present model may play some role in the optimum design of drumlike silencer. Besides, the cavity size and the parameter of the drumlike silencer are very impossible to obtain a width bank in low frequency.