Experimental study of the active sound transmission reduction through a double panel test section

The present study addresses the reduction of the sound transmission through an aircraft fuselage test section by means of a combined active noise and vibration control system, so as to reduce the noise level inside the passengers’ cabin. Experiments prove that control loudspeakers and error microphones in the trim cavity yield higher reductions in the radiated sound power than control shakers and error accelerometers on the trim panel. This conclusion remains valid when the skin and the trim panel are mechanically connected by means of four vibration isolators, and when the cavity is filled with thermal insulation blankets. It also appears that, in case of an active cavity noise control system, there exists an almost linear relation between the reduction of the acoustic potential energy in the cavity and the reduction of the radiated sound power. The optimised control system performs much better than a control system with sensors and actuators in arbitrarily chosen positions. * Research Assistant of the Fund for Scientific Research Flanders (Belgium) (F.W.O.)