Feasibility of the Full-Rank Fixed-filter Approach in the Active Control of Noise Through Open Windows

Successful implementation of active noise control (ANC) systems is dependent on their practicality. ANC systems that attenuate environmental noise through open windows of urban accommodation should ideally avoid the use of error microphones for the ease of implementation and maintenance. To remove the error microphones, control filters can be fixed after training with steady-state filters for various types of noise (e.g., different angles of incidence). The trade-off of such a fixed-filter, however, is the degradation in noise attenuation performance. Using a multichannel control formulation of tonal disturbances, a fixed-filter formulation is compared with the exact least squares solution in a 2D window finite element method (FEM) simulation. The results have preliminarily shown that the fixed-filter approach can theoretically yield 10 dB of attenuation for low frequencies at multiple incident angles. A theoretical performance limit of the fixed filter approach is obtained with the FEM simulation.