Progress of research on active noise radiation control with reflecting surfaces

The effect of reflecting surfaces on the peformance of active noise radiation control attracted attentions more than 20 years ago and there has been a lot of research on the area since then; however, successful applications are rarely reported. This paper first reviews the history of the research on active noise radiation control with reflecting surfaces, and then introduces recent progresses on this area at Nanjing University. The first progress is that the mechanism of noise reduction enhancement by introducing a refecting surface against the primary source in a multi-channel active sound radiation control system is analyzed. The second progress is that the noise reduction improvment by introducing an extra vertical reflecting surface to an active noise radiation control system near one existing horizontal surface is studied and the effects of the system orientation and the primary source location are discussed. The last progess is on increaseing the noise reduction by employing a finite size reflecting surface for the primary source on ground.