This Small Business Technology Transfer (STTR) Phase I project seeks to demonstrate the concept of a multipurpose active noise control module with broad application to a variety of environments and markets requiring acoustic noise control. Digital Signal Processors (DSP) have matured to the point where active noise reduction (ANR) based on least mean square (LMS) filters is viable. However, traditional LMS filters do not respond effectively to non-stationary signals, thus outside of telephony, commercial DSP-based noise control products employing adaptive feedforward control are unavailable. This project seeks to develop an ANR module that implements an innovative adaptive filter based on a patented Lyapunov tuning method. This method improves low frequency noise reduction performance significantly over traditional feedforward LMS filters or feedback ANR, and it enhances the LMS filter.s ability to track and effectively cancel non-stationary noise. This Phase I STTR seeks to evaluate the concept of a general purpose DSP module for ANR using Lyapunov-tuned filters that can be applied to a variety of open space or source noise cancellation problems. Open space ANR provides noise attenuation within a specified volume, while source cancellation reduces source noise created by heavy or light machinery. Phase I tasks focus on evaluating the potential for a plug-and-play module that, due to innovative LMS filters, can accommodate a variety of noise source characteristics and a range of dynamics of the acoustic environment in which the module is used. The research and eventual product meets a significant societal need for noise abatement technology to protect against noise and vibration, reduce occupational hearing loss, and increase human effectiveness in noisy environments. The applications for this general-purpose ANR module range from providing a quiet zone in the space around a passenger's head in the cabin of an aircraft or construction vehicle to acoustic and vibration protection of sensitive instrumentation that is subject to noise and vibration. The module serves the noise control consulting industry by providing a means of rapid deployment of effective retrofit ANR solutions for reducing noise due to mechanical equipment and ducting, in high noise cabins (aircraft, vehicle, and construction equipment), and by creating quiet spaces in manufacturing/industrial settings, airports, and office buildings.
