Acoustical properties of honeycomb structures filled with fibrous absorptive materials

The acoustical properties of the honeycomb structures filled with fibrous absorptive materials are theoretically investigated in the present paper. Since the fibrous materials are divided into periodical spaces, the model is developed based on a unit cell of the whole structure. The fibrous material in the honeycomb structure is modeled by applying the equivalent fluid theory with the obliquely incident sound existing on the periodical spaces in the form of standing wave. The energy flux is then obtained by the pressure and velocity at the fluid-structure interface, upon which the sound absorption coefficient and transmission loss is favorably calculated. The effects of the structure parameters on the acoustical properties are also discussed in the present paper. Results show that the hybrid structure has a better sound absorption ability than only fibrous material.