Active noise control in large industrial halls

Active noise control has been gaining significant interest in recent years as a mean of protection of humans against exposure to excessive low-frequency acoustic noise. It is particularly appreciated in environments were sufficient passive isolation of the humans from the noise source or vice versa is technologically unfeasible or not ergonomic. The paper concentrates on a very particular problem of noise control in large industrial halls. In cited examples noise levels reaches 120 dB what makes communication between workers impossible, and according to regulations significantly limits allowed work time. Necessity to move around machines generating different types of noise, feasibility of control at a small distance from secondary sound sources, dust, moisture and varying temperature influencing properties of the secondary sound sources, time-varying properties of the acoustic field, etc. complicate control significantly. The paper summarizes a research performed to approach the problem and presents guidelines for control system.