Investigation of the Variation in Insertion Loss of Vertical Noise Barriers for High-speed Railways at Different Levels of Sound Transmission Loss

Abstract The present study investigates the impact of sound transmission loss of vertical noise barriers for high-speed railways on insertion loss at various speed grades and heights. The findings reveal an initial increase in insertion loss followed by a plateau as sound transmission loss improves. A threshold value exists for weighted sound transmission loss, beyond which the insertion loss remains relatively constant. This threshold referred to as the minimum weighted sound transmission loss decreases with increasing train speeds and increases with higher noise barrier heights. The variation in insertion loss was calculated for noise barriers at heights of 2m and 3m under different sound transmission loss conditions, using measured sound source data corresponding to train speeds of 150km/h, 200km/h, 250km/h, 300km/h, and 350km/h. By polynomial fitting, at a train speed of 400 km/h, the minimum weighted sound transmission loss for 2m and 3m high noise barriers are determined to be 20dB and 21dB respectively.