The vibro-acoustic characteristics of a finite pipe baffled with an elastic plate were investigated under the consideration of the fluid which interacts both with the pipe and the circular plate. The coupled system model of structure and sound were established based on the Finite Element Method(FEM) .Concentrating on the sound energy and radiation impedance of the opening of the pipe system under the acoustic excitation of a plane wave, different coupled conditions were analyzed respectively, which are the pipe fixed, the plate fixed and the full coupled condition. The results showed that: the sound power is predominantly radiated by the fluid rather that the structure under the acoustic excitation in the low frequencies we concerned; the vibration of the elastic plate has effectively influenced the sound power and the radiation impedance response of the coupled system although the sound energy radiated is much less than the fluid, further study indicated that the symmetric bending mode has a remarkable effect on the peak frequencies of the sound power response; and the interaction of the pipe and the internal fluid has enhanced the sound energy transmitted from fluid to the elastic plate. The responses of the radiation impedance have coincidence peak frequencies with the responses of the sound power.

fluid-filled pipe; elastic plate; sound power; sound and structure interaction; radiation impedance