This paper presents the analysis of quiet zones in broadband diffuse fields using two- and three-channel systems. An optimization method combining a neural network with a search algorithm has been used to design quiet zones in broadband diffuse fields. Simulation results using the proposed method are presented. Experiments are also carried out to validate the simulation results. The results show that a good attenuation in the desired zone of quiet over space and frequency is achieved using a two-channel system. However, a better performance could be achieved using a three-channel system. Also, the shape and location of quiet zones over space and frequency could be controlled by using the proposed method. The results also show that the shape and size of 10-dB quiet zones are both similar in simulations and experiments. The main contributions of the paper are that a novel method of designing quiet zones in broadband diffuse fields is proposed and the performance of the active systems is analyzed through computer simulations and experiments.