Preliminary experimental tests in hemi-anechoic chamber for active noise control inside the cabin of a tractor

In recent years, increasing attention has been paid to vibration and acoustic noise control in industrial applications. The control of these phenomena allows to preserve the comfort and the health of people subjected to long periods of noise exposure and to a high level of disturbance. One example is the case of agricultural operators, exposed to loud noise for several hours per day. To solve this problem, active noise control (ANC) represents a valid solution in order to attenuate the noise in the low frequency range. In this paper, a preliminary evaluation in a hemi-anechoic chamber of the effectiveness of an ANC system is carried out for the case of a tractor cabin. A full experimental analysis is performed with stationary and transient disturbances generated by a simulated noise source (dodecahedron) placed outside the cabin, with both narrowband components and broadband noise. An ANC system with feedforward FXLMS algorithm is developed on a real-time target with FPGA for the reduction of noise at the driver's head position. The secondary paths are estimated with an offline technique and the evaluation of the effect of the presence of the head is investigated. The results show that the system is very effective for tonal components and pseudo-random noise.