Sound diffraction by multiple wedges and thin screens

Kim, Hyun‐Sil; Kim, Jae-Sueng; Kang, Hyunju; Kim, Bong-Ki; Kim, Sang-Ryul

doi:10.1016/j.apacoust.2005.01.004

Cited by 18 publications

(18 citation statements)

References 9 publications

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“…When multiple diffractions take place, the resulting sound pressure can be solved iteratively. [25][26][27] Without the reflecting surface, the acoustic properties of the secondary source can be easily obtained from the direct wave and the reflecting wave from the ground.…”

Section: Introductionmentioning

confidence: 99%

A mechanism study of sound wave-trapping barriers

Yang

Cheng

2013

The Journal of the Acoustical Society of America

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The performance of a sound barrier is usually degraded if a large reflecting surface is placed on the source side. A wave-trapping barrier (WTB), with its inner surface covered by wedge-shaped structures, has been proposed to confine waves within the area between the barrier and the reflecting surface, and thus improve the performance. In this paper, the deterioration in performance of a conventional sound barrier due to the reflecting surface is first explained in terms of the resonance effect of the trapped modes. At each resonance frequency, a strong and mode-controlled sound field is generated by the noise source both within and in the vicinity outside the region bounded by the sound barrier and the reflecting surface. It is found that the peak sound pressures in the barrier's shadow zone, which correspond to the minimum values in the barrier's insertion loss, are largely determined by the resonance frequencies and by the shapes and losses of the trapped modes. These peak pressures usually result in high sound intensity component impinging normal to the barrier surface near the top. The WTB can alter the sound wave diffraction at the top of the barrier if the wavelengths of the sound wave are comparable or smaller than the dimensions of the wedge. In this case, the modified barrier profile is capable of re-organizing the pressure distribution within the bounded domain and altering the acoustic properties near the top of the sound barrier.

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Section: Introductionmentioning

confidence: 99%

A mechanism study of sound wave-trapping barriers

Yang

Cheng

2013

The Journal of the Acoustical Society of America

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“…Solve the linear equations, and put the obtained boundary sound pressure p(r1, r0), p(r2, r0), ..., p(rN, r0) into equation (6), then for an arbitrary point in area V, its sound pressure p(r, r0) can be calculated.…”

Section: All Elements In Matrix [A] Vector [P] and Vector [G]mentioning

confidence: 99%

“…It is common in practical application to figure out the diffraction attenuation of sound waves from obstacles (such as sound barriers and buildings). After years of research, scholars have proposed lots of methods to calculate the attenuation of acoustic diffraction by obstacles, among which the empirical formula method [1], the Biot-Tolstoy method [2], the Hadden-Pierce method [3,4] and the geometrical theory of diffraction (GTD) [5,6] have been commonly used. As another common and effective numerical method, the boundary element method (BEM) has been nowadays widely used for this kind of problems with high calculation accuracy and excellent adaptability to complex boundaries.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Numerical Integration Accuracy and Sound Frequency on Computed Results of Acoustic Diffraction Problems with the Boundary Element Method

Li¹,

Wang²,

Cai³

2016

Advances in Computer Science Research

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Abstract-The boundary element method (BEM) using collocation with constant elements has been adopted to calculate the insertion loss of a sound barrier in a twodimensional model. Analysis has been done on how the results obtained with BEM are affected by the numerical integration accuracy. First, the precision of all elements in matrix which were obtained through integration of equations with numerical integration approaches is directly influenced by the integration accuracy, which further affects the final results. Second, Two numerical integration methods, midpoint rectangle rule and composite four-point Gaussian quadrature rule, have been compared in this work. The number of integration points has relatively little effect on the results, and the composite four-point Gaussian rule has a higher convergence rate than the midpoint rectangle rule. Moreover,a comparison of wedge insertion loss calculated with GTD and BEM for different frequencies and different BEM element lengths has shown that: for wedge diffraction problems, it is necessary to ensure the element length is below 1/20 wavelength and consider the impacts of characteristic frequencies.

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“…In a first step, ground reflection is ignored. According to the literature [21,22,23,24], A bar,f lat,0 can be expressed with high accuracy by equation (4):…”

Section: A Barmentioning

confidence: 99%

Urban Background Noise Mapping: The General Model

Wang¹,

Botteldooren²,

Renterghem³

et al. 2014

Acta Acustica united with Acustica

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Surveys show that inhabitants of dwellings exposed to high noise levels benefit from having access to a quiet side. However, current practice in noise prediction often underestimates the noise levels at a shielded façade. Multiple reflections between façades in street canyons and inner yards are commonly neglected and façades are approximated as perfectly flat surfaces yielding only specular reflection. In addition, sources at distances much larger than normally taken into account in noise maps might still contribute significantly. Since one of the main reasons for this is computational burden, an efficient engineering model for the diffraction of the sound over the roof tops is proposed, which considers multiple reflections, variation in building height, canyon width, façade roughness and different roof shapes. The model is fitted on an extensive set of full-wave numerical calculations of canyon-to-canyon sound propagation with configurations matching the distribution of streets and building geometries in a typical historically grown European city. This model allows calculating the background noise in the shielded areas of a city, which could then efficiently be used to improve existing noise mapping calculations. The model was validated by comparison to long-term measurements at 9 building façades whereof 3 were at inner yards in the city of Ghent, Belgium. At shielded façades, a strong improvement in prediction accuracy is obtained.

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Sound diffraction by multiple wedges and thin screens

Cited by 18 publications

References 9 publications

A mechanism study of sound wave-trapping barriers

A mechanism study of sound wave-trapping barriers

The Influence of Numerical Integration Accuracy and Sound Frequency on Computed Results of Acoustic Diffraction Problems with the Boundary Element Method

Urban Background Noise Mapping: The General Model

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