ABSTRACT
This chapter introduces a model for describing a noise field that has sound from many directions, and provides formulae to carry out simulations and designs for three-dimensional virtual sound barrier systems. It illustrates the physical requirement for the implementation of virtual sound barrier systems in the middle audible frequency range. Since a virtual sound barrier system is usually far away from the primary source, the mechanism is generally an absorption or reflection of the sound energy of the primary source, rather than reducing the impedance seen by the primary source. The chapter examines a hybrid virtual sound barrier where part of the system is an active noise control system that consists of arrays of loudspeakers and microphones, and the other part of system is a reflective surface. The orientation of the noise sources and the secondary sources with respect to each other and to the surface influence the control performance significantly.
