Acoustic Performance Optimization Of Noise Barriers With Top Covered With Resistant-Optimized Quadratic Residue Diffusers

As an efficient method to prevent traffic noise, noise barriers havebeen commonly used. Though it is relatively passive to construct noisebarriers to control traffic noise, they are very effective to improve theliving environment and the office environment which along the roads.Traffic noise reaches to the point behind the sound barrier mainlythrough transmission, reflection and diffraction. Diffraction is one of themain factors which reduce the insertion loss of the noise barrier. Andbased on this, the research of the top structure of noise barriers become theresearch hot spot. The domestic and international research shows that mostnoise barriers can reduce the high frequency noise significantly, but theeffect to the low frequency is not obvious. The traffic noise mainlyconcentrated in the low frequency, so it is necessary to reduce the lowfrequency noise caused it.According to characteristic of traffic noise which focuses on middleand lower frequency, a noise barrier with Quadratic Residue Diffuser wasapplied. We use SYSNOISE which is a kind of acoustic simulationsoftware to calculate the noise barrier model which QRD was applied on.According to the test in the impedance tube and the semi-anechoic room,we also analysis the absorption coefficient of QRD and the noise reductionperformance of noise barrier with QRD on itSYSNOISE simulation software was used to calculate the insertionloss of the erect noise barrier and the noise barrier with QRD top. Theexperimental results show that while the QRD was used as a top on the noise barrier, the insertion loss was3-7dB higher than the erect one.The experimental results in the impedance tube shows that whenQRD was composited with perforated plate and microperforated plate, thecomposite structure presented the performance of both the QRD and theperforated plate and microperforated plate. Both the absorption peak andthe half-peak width were highly improved. The absorption peak wasimproved to0.6from0.2. And also, we can get that the specific acousticimpedance was in accordance with the acoustical absorption coefficient.The frequency bandwidth of the acoustic resistance amplitude was in theabsorption coefficient half peak width.While QRD was combined with the resistance structure such asperforated plate and microperforated plate, the noise reductionperformance of the noise barrier with the composite structure was highlyoptimized. The composite structure with the microperforated plate whichthe thickness is0.8mm and the perforated percentage is2%was the beststructure. And the insertion loss of this composite structure is5dB higherthan the noise barrier just with the QRD.The noise barrier with QRD top has a high noise reduction thantraditional noise barrier, so it has a wide prospect. Meanwhile, the QRDnoise barrier will also provide the theory and practice reference toresearchers in the field of barrier design.