Abstract
The cars structures are made of thin ribbed plates. Due to the road excitations, transmitted by the wheels, these types of plates radiated noise, which pollute the environment. Therefore the paper reveals the acoustic fields radiated by such plates as elements of the cars structure. In the ribbed plate system, the reinforcing beam affects both the propagation of the flexural waves in the plate, as well as the sound radiation from the structure. A subsonic incident flexural wave in the plate impinging on the beam discontinuity generates transmitted and reflected propagating waves, and transmitted and reflected near-field waves in the plate. The scattering of structural wave field gives rise to supersonic wave-number components of the plate vibration, which subsequently leads to sound radiation into the surrounding field. Two structural coincidence conditions have been identified in this paper. Physically, they correspond to the optimal trace wave matching the flexural waves in the plate and the flexural and torsional waves in the beam. This paper reports for the first time a new observation concerning the characteristics of the radiating sound fields that occur because of structural coincidence conditions.