A comparison of ISO 9613-2 and advanced calculation methods: Predictions versus experimental results (original) (raw)
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The process of performing an Environmental Impact Assessment includes the study of noise propagation. Often, the path from a noise source to a noise sensitive location involves complicated mechanisms of sound transmission. These mechanisms may relate to diffraction & reflections from obstacles (natural or man made), ground properties, and meteorological conditions. The International Standards Organization proposes with standard ISO9613-2, methods by which to calculate these effects. While they are relatively easy to implement, they underestimate the true workings of the aforementioned mechanisms. In this paper, we present the OTL - Terrain software application, which accurately and precisely simulates outdoor sound propagation. The software application can be used for the prediction of environmental noise and the design of control measures. OTL - Terrain is an application which uses geometrical acoustics (GA) and models the propagation of sound in terms of rays. The tool makes use of the image source method (ISM) combined with visibility tracing techniques to implement a novel method of path-detection, taking both reflection and diffraction effects into account. Calculations utilize the predicted reflections from finite-sized objects with Fresnel zone corrections, an unlimited order of diffraction, and atmospheric turbulence. This paper presents a comparison of the predictions made by the OTL – Terrain application, the methods proposed by ISO, and the published results from experimental data.
Comparison of Some Methods Used for Prediction of Atmospheric Sound Propagation
Canadian Acoustics, 1997
The sound field in inhomogeneous atmospheric conditions above an impedance plane is computed using three different numerical procedures, to assess their advantages and disadvantages. Two implementations of the parabolic equation are considered, the Green's function method and a Crank-Nicolson method; these are contrasted with a version of the fast field program. As test cases, both upward and downward refracting conditions are considered, with and without turbulence. Calculations made using the Green's function implementation are considerably faster, making it the method of choice when large numbers of calculations (as when many realizations of turbulence are required) are necessary. However, considerable care is required in setting computational parameters and parallel calculations with one of the other techniques for validation is advisable.
Influence of Atmospheric Conditions on Sound Propagation - Mathematical Modeling
2015
Propagation of sound in atmosphere is influenced by many factors such as air temperature, relative humidity, air velocity and direction as well as temperature inversion. Intensity of sound disappears in depending on distance by atmospheric absorption and atmospheric turbulence. Many times it is difficult and sometimes impossible to determine the values of equivalent sound pressure levels (A) under different atmospheric conditions. To identifying changes caused by atmospheric conditions is preferred to use the programs for mathematical modeling. The differences of measured values of equivalent sound pressure levels (A) under various atmospheric conditions are not insignificant. When comparing favorable and unfavorable atmospheric conditions for propagation of sound, difference of values of equivalent sound pressure levels (A) may be up to 10 dB. Obviously under conditions that are placed on these measurements like relative humidity <95 % and air velocity <3 m.s -1 . This articl...