Active control of structure-borne and air-borne sound transmission through double panels

This paper presents a theoretical study of the active isolation of both structure-borne and air-borne noise transmission through a double panel system. The physical and geometrical characteristics of the system studied have been chosen similar to those of the fuselage of a civil aircraft. The total sound power transmitted by the double panel system has been used to evaluate the active control performance considering three different configurations for the control system: first, active mounts connecting the two panels driven to cancel the out-of-plane velocities at the connecting points on the radiating panel; second, loudspeakers placed between the two panels driven to cancel the acoustic pressure at specific points near to each control loudspeaker and third, simultaneous use of the active mounts and control loudspeakers systems. Also, the performance of the three control devices have been evaluated when total sound power radiation is minimised. The simulations carried out have shown that the control loudspeakers are able to produce large attenuation of the sound transmission at frequencies close to the mass-air-mass resonance of the double panel. The performance is significantly better if the loudspeakers are driven to minimise radiated sound power, rather than cancel pressure between the panels.