A platform for benchmark cases in computational acoustics

Solutions to the partial differential equations that describe acoustic problems can be found by analytical, numerical and experimental techniques. Within arbitrary domains and for arbitrary initial and boundary conditions, all solution techniques require certain assumptions and simplifications. It is difficult to estimate the precision of a solution technique. Due to the lack of a common process to quantify and report the performance of the solution technique, a variety of ways exists to discuss the results with the scientific community. Moreover, the absence of general reference results does hamper the validation of newly developed techniques. Over the years many researchers in the field of computational acoustics have therefore expressed the need and wish to have available common benchmark cases. This contribution is intended to be the start of a long term project, about deploying benchmarks in the entire field of computational acoustics. The platform is a web-based database, where cases and results can be submitted by all researchers and are openly available. Long-term maintenance of this platform is ensured. As an example of good practice, this paper presents a framework for the field of linear acoustic. Within this field, different categories are defined – as bounded or unbounded problems, scattering or radiating problems and time-domain as well as frequency-domain problems – and a structure is proposed how to describe a benchmark case. Furthermore, a way of reporting on the used solution technique and its result is suggested. Three problems have been defined that demonstrate how the benchmark cases are intended to be used

Time-domain structural vibration simulations by solving the linear elasticity equations with the discontinuous Galerkin method

In the field of building acoustics, an efficient solution of the linear elasticity equations for vibro-acoustic problems is of interest. The focus of this work is on the structural part, with plate vibra-tion problems in particular. The linear elasticity equations in the stress-velocity formulation are solved in the time-domain for the three-dimensional plate problem. The numerical solution is obtained through the Runge-Kutta discontinuous Galerkin method, which has the potential to be highly parallelizable and thereby computationally very efficient. Numerical aspects of applying the discontinuous Galerkin method to this problem are discussed, especially on the force excita-tion and the boundary conditions of the plate problem. The accuracy of applying the discontinu-ous Galerkin solution is presented by comparing its results to results from analytical solutions. Several scenarios of plate variations with different boundary conditions are simulated to demon-strate the capabilities of the method

Time-domain structural vibration simulations by solving the linear elasticity equations with the discontinuous Galerkin method

In the field of building acoustics, an efficient solution of the linear elasticity equations for vibro-acoustic problems is of interest. The focus of this work is on the structural part, with plate vibra-tion problems in particular. The linear elasticity equations in the stress-velocity formulation are solved in the time-domain for the three-dimensional plate problem. The numerical solution is obtained through the Runge-Kutta discontinuous Galerkin method, which has the potential to be highly parallelizable and thereby computationally very efficient. Numerical aspects of applying the discontinuous Galerkin method to this problem are discussed, especially on the force excita-tion and the boundary conditions of the plate problem. The accuracy of applying the discontinu-ous Galerkin solution is presented by comparing its results to results from analytical solutions. Several scenarios of plate variations with different boundary conditions are simulated to demon-strate the capabilities of the method

Vegetation in urban streets, squares, and courtyards

One of various ways in which vegetation cover used in the greening of urban areas can help improve the health and well-being of people is in how it changes the acoustic environment. This chapter presents findings of computer simulations and scale modelling to examine and quantify the effectiveness of green roof and green wall (vertical garden) systems in reducing road traffic noise for streets, squares, and roadside courtyards. Noise reduction by sound absorption in reflected and diffracted (over roofs) sound paths is investigated. Particular attention is paid to the importance of vegetation placement relative to the receiver/listening positions. Because the soil substrate used for the vertical walls has good sound absorption properties, it also can be used for green barriers. In this chapter, the effects of a low barrier made of green wall substrate are studied for an installation on the ground and on the top of buildings surrounding a courtyard

Ten questions concerning computational urban acoustics

The sound environment in urban areas is complex, as caused by many sources of sound and influenced by a variety of acoustic propagation effects. In order to combat noise and create acoustic environments of high quality, it is of utmost importance to be able to predict the time dependent sound field in such areas. Engineering methods are useful for a fast analysis and noise mapping purposes, but remain tools with limitations. Besides, computational modelling of urban acoustics, i.e. the group of wave-based solution methods, has obtained its role for complex environments as well as for research purposes. These computational models have become more mature in the recent decade. This paper addresses questions that are of interest for all scientists and research-oriented engineers in this field, as well as researchers in related fields of urban physics. The questions relate to the need for computational methods, the relevance of including various urban propagation effects in computational modelling, and to the preferable computational methods and approaches to use. Answers are based on scientific work by the author and many other urban acoustic researchers, and will also contain visionary opinions of the author

Acoustic modelling of indoor and outdoor spaces

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