1. Overview

The dissipation of sound energy with distance is the principle upon which noise barriers are based.  It implies that higher barriers muffle noise more effectively.  If the receptive point is at a higher position than the sound source or vice versa, then the noise barrier cannot effectively reduce noise. Noise proof road tunnels can effectively arrest noise by minimizing the diffracting sound.

2. Technological Adequacy Outline

Usage

The soundproof tunnel is made with zinc-coated corrugated steel sheets and H-beams, and mitigates the noise of cars and trains.  Also, it substantially curbs the blasting engine noise of very hi-speed rails.

Applications

Protection of residential and commercial areas from vehicle noise.  Dampening of hi-speed train engine noise.  Preventive measure against the possible occurrence of landslides at tunnel ends.  

Merits

The soundproof tunnel effectively traps noise and goes well with the surrounding environment.  In addition, it is easy to install lights and openings in the tunnel to secure safe driving conditions from rain and ice.

3. A Comparison of Soundproofing Effects

Noise Barrier

The height of barriers can only reach 15 meters under the current design and construction conditions.  
There are areas where sound cannot be dampened due to direct sounds from the sound source. 
Soundproofing effect decreases at the ground and lower levels due to a diffraction of noise. 

Tunnel

Effective sound reduction is achieved as the direct sound from the source is blocked. 
As the diffraction of sound is checked, a satisfactory reduction in noise pollution is possible at the  ground and lower levels.
Lowered height allows it to better harmonize with the environment and enhances the structural stability of the tunnel.