Active noise barrier based on the boundary surface control

Based on the principle of the boundary surface control, it is possible to make a surface which reflects acoustic energy flow by controlling the pressure and its gradient on the surface. In order to realize this method, a system has to be made using multiple speakers and multiple microphones. The system should be adjusted so that the output signals of the multiple microphones which are located on the surface considered to be the location of the barrier are minimized. By changing the distance between the microphones, the best effect of the active noise barrier can be obtained. For instance, in a level lower to the ground, many microphones are needed to control higher frequencies. On the other hand, in a level higher from the ground, it is not necessary to use so many microphones to control lower frequencies. The merit of this method is that the apparent height of the barrier, depending on the frequency considered, can be changed. In this paper, the active noise barrier based on the boundary surface control ...