Active noise control on systems with time-varying sources and acoustical elements

Abstract

An active noise control system has been developed based on a system identification concept using a recursive adaptive filter to model the direct and feedback elements of an acoustic system. An independent random noise source is used with a second adaptive filter to provide a model of the output transducer and error path transfer functions. This system has the ability to continuously cancel narrow band and broadband noise. The system identification configuration combined with adaptive filter techniques enables the system to respond quickly and accurately to changes in time-varying sources, such as frequency or amplitude, and changes in the acoustical system, such as temperature. Noise reduction results will be presented. The system capabilities will be demonstrated on a variety of time-varying sources and time-varying acoustical elements. The ability of the system to track these changes in real-time as well as implications for actual applications will be discussed.