ACTIVE NOISE CONTROL IN PROXIMITY OF A TRACTOR OPERATOR’S HEAD

摘要

A bstract . To reduce the noise level near the head of agricultural machine operators, an active noise control (ANC) system, which uses sound wave interference, was developed. This system incorporates a recurrent least square (RLS) algorithm into the feedback control loop. The ANC system was developed using a TMS320C25 high-speed digital signal processor (DSP). The noise-reduction effect of this system was examined at points near the ears of a tractor operator. When the engine of a stopped tractor was running at rated speed, the overall sound pressure level (SPL) was reduced by about 5 to 6 dB, and the maximum SPL decreased approximately 18 dB. Since the computing speed and operational precision of the chosen DSP were limited, the noise-reduction effects of the system were not yet achievable for practical applications. As a result, the basis for future improvement and possible commercialization of the system using the TMS320C60 DSP, which has higher operational performance, is presented.