25. Modular sound insulating barriers designed to replace existing noise barriers on viaducts

Future large-scale renovations on Shinkansen (bullet train) viaducts are expected to include replacement of aging noise barriers. This requires a new type of barrier that is easier to install and also more effective at reducing noise levels. We have developed a modular sound insulating barrier intended as a replacement for existing noise barriers (see Figure 1).

The modular units are essentially tall posts of identical width, which are linked together to form a contiguous wall alongside the railway tracks. Structural strength is provided by corrosion-resistant steel panels treated with an anti-rust coating that weigh about a third as much as traditional concrete noise barriers while still being sufficiently sturdy. Thanks to the lightweight design, our barriers can be assembled and erected manually by workers, without the need for heavy machinery, provided that sufficient measures for safety considerations can be made.

Soundproofing is provided by layers of laminated polyester fiber sound absorption material with differing characteristics on the side facing the tracks (see Figure 1). Sound absorption is equivalent to or better than glass wool, used extensively in noise barriers for many years (see Figure 2). By integrating sound insulating barriers with sound absorption panels, we can reduce noise levels along the entire polyester surface facing the tracks, eliminating the need for additional sound absorbing work. We trialed the modular barrier system on a commercial line, using a directional microphone to measure noise levels. The equivalent continuous A-weighted sound pressure level averaged from nine passing trains (single train sets) was 2.4 dB lower compared to conventional concrete noise barriers (see Figure 3).