This paper demonstrates the use of RAINBOW and THUNDER actuators as acoustic control sources in the real-time control of low frequency harmonic interior noise. The former actuator drives a flat acoustic piston while the latter drives a conventional speaker cone. The low-profiled and lightweight nature of these actuators makes them suitable for aircraft applications. The two devices have been used successfully for active noise cancellation inside a duct and a cylindrical enclosure. This paper presents results of the real-time noise control experiments.

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This paper presents an experimental study of the shallow spherical shell piezoceramic RAINBOW actuator, to follow up the theoretical modeling and numerical studies of this actuator reported in a previous paper. A comparison of theoretically predicted and experimentally determined natural frequencies of the RAINBOW actuator with free edge boundary conditions is presented in the paper. Also presented are results from experiments performed on a prototype of a low profile piezoelectrically driven baffled acoustic piston developed at the Smart Trim Technology Laboratory. Experimentally generated volume velocity curves of the piston are presented. The possible use of this device in active noise control applications is discussed.

This paper presents experimental results from a demonstration of feedback control experiments on an open-ended acoustic duct, using nodally placed colocated actuator-sensor pairs. The disturbance signal used in the experiments is bandlimited and random. The first three modes undergo as much as 20 dB attenuation. The simplicity of the nodal control together with the spatially global sound reduction makes this a suitable technique for suppressing low frequency broadband duct noise.