Structure-borne noise of fully enclosed sound barriers composed of engineered cementitious composites on high-speed railway bridges

Abstract

Fully enclosed sound barriers (FESBs) have been gradually introduced to sensitive sections alongside high-speed railways because of greater noise mitigation compared with vertical sound barriers. However, metal sound insulation boards (SIBs) commonly used in FESBs have poor durability and high cost, and prominent vibration problems induced by high-speed passing trains can lead to deformation fatigue damage of structural components of FESBs, and also bring about vibroacoustic radiation, namely, structure-borne noise. To reduce the defects of metal SIBs, high-strength and tough low-viscosity concrete SIBs with engineered cementitious composite (ECC) has been developed. To determine the characteristics of structure-borne noise generated by ECC FESBs arranged on high-speed railway bridges (HSRB) and their influence on the acoustic environment alongside the track line, systematic field tests were implemented targeting the vibration and noise of FESBs. A validated numerical model of structure-borne noise was formulated using the fast multipole boundary element method (FMBEM). The time–frequency distribution characteristics and the correlation between vibration and structure-borne noise are thoroughly analyzed. The structure-borne noise of HSRBs with ECC FESB, metal FESB and without FESB were compared, and the influences of ECC FESB at typical points in the acoustic field were quantified using panel acoustic contribution (PAC) analysis. The variation in the structure-borne noise with train speed were also examined. Results showed that the structure-borne noise radiation to the acoustic field were changed owing to the installation of FESBs, and the overall sound pressure level (OSPL) increased by 2.3 dB near the bridge components, 12.8 dB at 1.2 m above the ground, and 19.5 dB above the track. The structure-borne noise of ECC FESBs has become the main acoustic contributor in acoustic field and accounts for 64.1% and 82.7% for locations above the ground and for the points which are horizontally above the track’s center line at a distance of 25 m, respectively. The structure-borne noise of ECC FESB is higher than that of metal FESB by less than 1.4 dB. The OSPL of ECC FESB on the bridge increased by approximately 1.4 dB following a train speed increase of 20 m/s. This research is anticipated to be used as a reference in future studies of the acoustic characteristics of structures with large volumes using new materials.