Adaptive passive acoustic attenuation system

Abstract

An adaptive passive acoustic attenuation system implements control techniques to facilitate practical use of adaptive passive acoustic attenuation in industrial and commercial applications. The system includes multiple banks of multiple adjustable tuners that are used to passively attenuate an acoustic disturbance (e.g. a tone) propagating through an acoustic plant. All of the tuners in one of the banks are contemporaneously adjusted during an adaptation scan while the tuners in the other banks remain stationary. The process is then carried out for the other banks of adjustable tuners. The number of adjustable tuners per bank is chosen so that adaptation scans of the tuners in the respective bank create observable changes in acoustic levels to enable adaptation. Multiple sets of multiple banks of adjustable tuners can be provided to attenuate multiple disturbances propagating through the acoustic plant. Signals from error sensors are filtered and processed to account for acoustic energy in the plane wave mode as well as higher order modes. Adaptation accuracy is improved by a double scan technique, and by accounting for time-varying acoustic disturbances. Mechanical malfunctioning of the adjustable tuners is reduced by an exercising technique, and the control model implements a lock-out scheme for mechanically malfunctioning tuners.