A theoretical analysis of the acoustic field in a three-dimensional interior space is carried out for the low frequency range of low modal density. By using the boundary element method optimum velocities of control sources and the acoustic potential energy at some field locations are evaluated. Simulations are performed for overdetermined system as well as underdetermined ones. Based on these informations, the maximum possible amount of noise reduction is predicted by comparing the simulation results for various control source locations. The results show that the control source should be close to the noise source as well as located to the antinode of the involved acoustic mode to achieve the best noise reduction. Experimental results are in reasonable agreement with theoretical ones. The suggested technique in this study would be a promising tool for searching 'good' secondary source sites to be on the boundary.
