Noise suppression of a dipole source by tensioned membrane housing

摘要

Reducing the ducted-fan noise at the low frequency range remains a big technical challenge. Thisrnstudy presents a passive approach to directly suppress the sound radiation from an axial-flow fanrnof dipole nature housed by a tensioned membrane backed with a cavity. The use of thernmembrane not only eliminates the aerodynamic loss of flow, but also provides flexibility inrncontrolling the range of the stopband with high insertion loss by varying its tension and mass. Arntheoretical model is presented which allows the performance of the proposed device to bernexplored analytically. With the proper design, this new device can achieve better noise reductionrnthan the empty expansion cavity. Through the detail modal analysis, even in-vacuo modes of thernmembrane vibration are found to play an important role on the suppression of sound radiationrnfrom dipole source.