Design and Development of an Acoustic Antenna System for Industrial Noise Source Identification

Abstract

In the Netherlands, being a very populated country, noise pollution from industry is of mayor importance. In order to protect the community against severe noise levels due to industry, the immission levels are not allowed to exceed certain values. To verify if these levels are not too high, it is often necessary to measure the immission levels near dwelling areas. However, with conventional sound measuring equipment, only the total immission levels are found and the individual noise sources cannot be distinguished. The measurement sites can be at distances of several 100 m to more than 1 km from the industrial area of concern. Because of these large measurement distances it is necessary to have a high directivity of not more than a few degrees, to be able to distinguish between the various sources of interest. It must be noted that such a high directivity cannot be obtained with conventional directional microphones. Such devices have directivities of not better than about 60 degrees. For that reason we decided to develop SYNTACAN, an acoustic antenna system, based on the measurement of the spatial correlation function of the soundfield along the antenna [1]. The antenna consists of a sparsed array of 32 microphones, positioned in a row over a length of nearly 80 m. It has a theoretical resolving power of 1.5 ± 0.5° over a frequency range from 90 to 1400 Hz.