A low-cost digital signal processor-based earmuff using adaptive active noise control

摘要

This paper presents the design and implementation of a digital signal processor (DSP)-based feed-forward narrow-band noise canceling system using the Analog Devices ADSP-2181 EZ-KIT Lite developer's kit. The theory of adaptive noise control (ANC) is applied to an earmuff so that the entire system combines both passive and active techniques to reduce the harmful acoustic noise emitted by machinery and engines. The ANC developed uses a 100-tap finite impulse response (FIR) filter which encompasses the least mean square (LMS) and normalised LMS (NLMS) algorithms to adaptively `track' changing input conditions. The hardware and software aspects for real-time implementation, the signal conditioning circuits and the software developed for stereo multiplexing in the EZ-KIT Lite environment are presented. Performance results show significant improvements in noise attenuation levels when compared to use of a purely passive technique.