An analyses of the noise reduction effect of vegetation noise barrier using scaled model experiments

An adverse effect of urban elevated rail transit systems is the associated noise, which has become a source of environmental complaints. In order to effectively address this problem, an in situ experiment has been conducted on the elevated sections of Hangzhou Metro Line 1 involving three cases: a 2.2 m vertical noise barrier with integrated bed track, a 2.2 m vertical noise barrier with an elastic mat floating slab track, and a 5.1 m fully enclosed noise barrier with an elastic mat floating slab track. The noise reduction effects of the elastic mats and the two kinds of noise barriers for metro viaduct railway lines were evaluated, and the mechanisms of these countermeasures were analysed. The results show that elastic mats can effectively reduce the transmission of wheel–rail vibration energy into the bridge, thus decreasing bridge-borne noise; meanwhile, the elastic mats could lead to an increase in wheel–rail noise. An excellent noise reduction effect was achieved in the area below and near the bottom of the bridge, while an increased noise effect was observed close to the area above and near the rail surface. The fully enclosed noise barrier controlled the propagation of wheel–rail noise more effectively than the vertical noise barriers, but no difference was found between these two kinds of noise barriers in controlling bridge-borne noise.

Download Full-text

Simulation Study on Noise Reduction Effect of Substation Noise Barrier

Vibration Engineering for a Sustainable Future ◽

10.1007/978-3-030-48153-7_42 ◽

2021 ◽

pp. 327-333

Author(s):

Xuan Cai ◽

Xuelei Zhan ◽

Yong Cai ◽

Li Wang

Keyword(s):

Noise Reduction ◽

Simulation Study ◽

Noise Barrier ◽

Reduction Effect

Download Full-text

Case study: Prediction and field tests of railway noise and effects of a low-height noise barrier

Noise Control Engineering Journal ◽

10.3397/1/376826 ◽

2020 ◽

Vol 68 (4) ◽

pp. 303-314

Author(s):

Yuna Park ◽

Hyo-In Koh ◽

University of Science and Technology, Transpo ◽

...

Keyword(s):

High Speed ◽

Field Tests ◽

Residential Areas ◽

Railway Systems ◽

Railway Noise ◽

Sound Levels ◽

Noise Barrier ◽

The Difference ◽

Reduction Effect ◽

The Impact

Railway noise is calculated to predict the impact of new or reconstructed railway tracks on nearby residential areas. The results are used to prepare adequate counter- measures, and the calculation results are directly related to the cost of the action plans. The calculated values were used to produce noise maps for each area of inter- est. The Schall 03 2012 is one of the most frequently used methods for the production of noise maps. The latest version was released in 2012 and uses various input para- meters associated with the latest rail vehicles and track systems in Germany. This version has not been sufficiently used in South Korea, and there is a lack of standard guidelines and a precise manual for Korean railway systems. Thus, it is not clear what input parameters will match specific local cases. This study investigates the modeling procedure for Korean railway systems and the differences between calcu- lated railway sound levels and measured values obtained using the Schall 03 2012 model. Depending on the location of sound receivers, the difference between the cal- culated and measured values was within approximately 4 dB for various train types. In the case of high-speed trains, the value was approximately 7 dB. A noise-reducing measure was also modeled. The noise reduction effect of a low-height noise barrier system was predicted and evaluated for operating railway sites within the frame- work of a national research project in Korea. The comparison of calculated and measured values showed differences within 2.5 dB.

Download Full-text

Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

Applied Sciences ◽

10.3390/app11093869 ◽

2021 ◽

Vol 11 (9) ◽

pp. 3869

Author(s):

Chen Niu ◽

Yongwei Liu ◽

Dejiang Shang ◽

Chao Zhang

Keyword(s):

Reynolds Number ◽

Drag Reduction ◽

Noise Reduction ◽

Channel Flow ◽

Superhydrophobic Surface ◽

Sound Field ◽

Flow Noise ◽

Slip Boundary ◽

Eddy Simulation ◽

Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

Download Full-text