Designing practical active noise control systems M. Cuesta, T. Bravo, P. Cobo, C. Ranz, and M. Siguero Instituto de Acústica, CSIC. Serrano 144. 28006 Madrid. SPAIN Abstract: This paper deals with the practical aspects of the design of two active noise control (ANC) systems to attenuate low frequency noise. In the first instance, a hybrid passive-active control system to reduce the noise radiated by a small generator has been designed. A SISO ANC system, in a side branch of the exhaust tube, attenuates some of the harmonics of the lowfrequency exhaust noise as much as 27 dB. In the second instance, a MIMO ANC system is designed to alleviate the booming inside a van. The booming is reduced more than 20 dB at the front seats. 1. Introduction Active noise control (ANC) techniques rely on the destructive interference between the existing, or primary, noise and the anti-phase, or secondary, noise set up by an electronic controller(Nelson and Elliott, 1992; Hansen and Snyder, 1997; Kuo and Morgan, 1996). The simpler adaptive ANC system processes a reference signal to generate the control signal that drives the secondary source. An error signal monitors the control performance. The adaptive filter must extrapolate the acoustic field from the reference sensor to the error sensor (primary path) and compensate for the transfer function between the control source and the error sensor (secondary path) (Cobo, 1997). Since ANC works best on low frequency noises, the active approach complements the traditional passive control methods. The aim of this paper is to illustrate the design of two ANC systems. In the first instance, a hybrid passive-active control system is designed to reduce the noise radiated b...
