People living in houses near a big factory complained about chattering of glass windows. At one of these houses, the SPL of low frequency noise was about 66 dB at 5.5 Hz and ground acceleration level was about 40 dB at 9 Hz in the horizontal direction. (0 dB acceleration = 10−5 m/s2). We found that the noise and ground vibration were caused by a big grinding mill in the factory, because both SPL and acceleration level at the residential district were considerably decreased when the mill was not in operation. We also confirmed that low frequency noise was not transmitted from the grinding mill directly, but was due to the resonant vibration of walls of the factory building. Two ideas are studied here to suppress the noise, one of which is to isolate the vibration of the grinding mill at its foundation, and the other is to improve the stiffness of the building frames to stop the wall vibration. As a result of the study, the latter method to increase the stiffness of the building was adopted. The SPL of low frequency noise near the wall was decreased.
Design of Intelligent Control System Using Acoustic Parameters for Grinding Mill Operation
