Mechanism of noise generation from a modular expansion joint under vehicle passage

The mechanism for the generation of noise from a modular expansion joint in a bridge under vehicle passage, which can cause an environmental problem, is investigated in experiments on a full-scale model of the joint. Noise and vibration characteristics of the joint model in the near field are identified by a series of car-running experiments associated with separate tests of the acoustic and dynamic characteristics of the joint. A modal analysis based on finite element modelling of the joint is also conducted and structure-borne noise radiation is discussed by correlating the dominant frequency components of the noise with the modal parameters. It is concluded that the noise from the top of the joint, dominant in the frequency range from 500 to 800 Hz, is caused by a sudden change in the pressure of air within the gap formed by the rubber sealing with two adjacent middle beams, and that the noise from the bottom, dominant in the frequency range below 200 Hz, is attributed mainly to sound radiation from the vibration of the middle beams.