Noise mitigation of Old Årsta railway steel bridge

With its central role in Stockholm's railway infrastructure, the Old Årsta bridge is busy around the clock. This 1929 steel bridge is owned and operated by the Swedish Transport Administration (Trafikverket) and recently underwent renovation work. Subsequently, a need for noise mitigation was identified. However, the infrastructural role made it a prerequisite that traffic could not be affected neither during investigation nor installation of mitigation means. A comprehensive pre-study of the noise issue was previously published at Internoise 2017. It led to the installation of a multi-component CLD solution (Constrained Layer Damping). This paper presents findings from measurements of noise and structural properties after the CLD installation. A satisfactory noise reduction was obtained, and various learning points are presented. The applied mitigation strategy, using different layers of temperature dependent viscoelastic polymers, appeared to be both efficient and practical.