Workers at factories may feel uncomfortable due to the influence of noise from the peripheral machines, but it is hard to select sound insulation panels as a noise countermeasure due to visual management and working reasons. In order to reduce the sound pressure in a specified area, we proposed an active noise control (in the following, ANC) system that is composed a feed forward type control method and a device arrangement determination method. In this article, we report about the control method that is stable and less susceptible to noise changes and the arrangement method derived from prediction of region effect by ANC. The ANC system reduced machine noises about 4 to 6dB in 100 to 300Hz on average of a specified area.
It is generally known that low-frequency sound is affected by natural winds when measured on site. In this paper, the estimation method of wind noise by natural wind was examined by wind tunnel experiment and field experiment, and the preparation procedure of the estimation methods was presented. In the field experiment, two types of estimation formulas with different category of surface roughness were constructed, and the correlation between the field measured values and the estimated values was examined. As a result, it was confirmed that there was a strong correlation between measured values and estimated values.