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

This paper presents the design and implementation of a digital signal proce ssor (DSP)-based feed-forward narrow-band noise canceling system using the Analog Devices ADSP-2181 EZ-KIT Lire developer's kit. The theory of adaptiv e noise control (ANC) is applied to an earmuff so that the entire system co mbines both passive and active techniques to reduce the harmful acoustic no ise emitted by machinery and engines. The ANC developed uses a 100-tap fini te impulse response (FIR) filter which encompasses the least mean square (L MS) and normalised LMS (NLMS) algorithms to adaptively 'track' changing inp ut conditions. The hardware and software aspects for real-time implementati on, the signal conditioning circuits and the software developed for stereo multiplexing in the EZ-KIT Lire environment are presented. Performance resu lts show significant improvements in noise attenuation levels when compared to use of a purely passive technique. (C) 1999 Elsevier Science B.V. All r ights reserved.