The noise of a machine under operating conditions can be categorized as structure-borne, i.e., caused by vibration due to vibrational sources, or airborne, i.e., caused directly by sound sources. By applying the principal component analysis with acceleration pickups and microphones, the number of independent vibrational sources and sound sources can be identified. Based on the frequency response functions between the vibrational sources and the accelerations against the impact or exciter excitation measured in advance, and those between the vibrational sources and the sound pressure at the observation point, first the input forces can be estimated using accelerations under operating conditions and then the ratio of structure-borne noise can be evaluated; furthermore the airborne noise can be obtained. Each contribution to the total noise can be identified every 1/3 octave bands. These results are confirmed by the boundary element method based on vibrational mode shapes and sound source.
展开▼
