Im Genehmigungsverfahren für den Bau hochliegender Schallquellen (z.B. Windenergieanlagen) muss der Nachweis geführt werden, dass von den Anlagen keine schädlichen Umwelteinwirkungen ausgehen. Es ist es daher notwendig, die Schallausbreitung derartiger Quellen grundsätzlich zu untersuchen. Eine Schwierigkeit stellt dabei die gekoppelte Wirkung von Temperatur-, Windgeschwindigkeits- und Windrichtungsprofil in Zusammenhang mit dem Bodeneinfluss auf die Schallausbreitung dar. Dieser zeitlich und räumlich variable Atmosphäreneinfluss wird insbesondere bei Langzeituntersuchungen der Schallimmission bisher nur unzureichend in den operationellen Modellen beschrieben. Das Ziel der Studie besteht deshalb darin, die gekoppelte Wirkung von Atmosphäre- und Boden-Einfluss auf die Schallausbreitung in einem Bereich bis zu 2 km Entfernung von der Schallquelle mit dem Modell SMART (Sound propagation model of the atmosphere using ray-tracing ) zu untersuchen. / The licensing procedure for the construction of high-placed sound sources (e.g. wind power stations) demands to proof that no (significant and) harmful impact on environment is outgoing from these systems. Therefore, it is necessary to analyse the sound propagation of such a kind of sources. In this context one central problem has to be managed: the coupled effect of temperature, wind speed and wind direction profiles combined with the influence of surface on sound propagation. The temporally and spatially variable influence of the atmosphere is only insufficiently described by the operational models, especially in relation to long-time investigations of sound immission. Consequently, the aim of this study was to investigate the coupled effect of atmospheric and surface influence on sound propagation up to distances of 2 km away from the sound source using the model SMART (Sound propagation model of the atmosphere using ray-tracing).

In dieser Studie wird ein Verfahren näher erläutert, welches im Rahmen einer Projektbearbeitung für die Bundeswehr entwickelt worden ist. Dieses Verfahren prognostiziert die Ausbreitung von Schießlärm unter besonderer Berücksichtigung der Einflüsse meteorologischer Verhältnisse (Schallwetter) und ermöglicht so die Prognose erhöhter Lärmbelastungen. Weiterhin ist mit diesem Verfahren auch eine regionale Einteilung eines Gesamtgebietes in schallklimatologisch ähnliche Teilgebiete möglich. Eine solche Untersuchung erfolgt durch die Analyse von Schalldruckpegeldämpfungskarten für eine Vielzahl von Atmosphärenstrukturen. Im Wesentlichen stützt sich das Verfahren dabei auf zwei Komponenten, auf das Schallausbreitungsmodell SMART (Sound propagation model of the atmosphere using ray-tracing) und das Anwendungstool MetaVIS (Meteorological attenuation visualization). Mit Hilfe des Modells SMART werden Schalldruckpegeldämpfungen berechnet, welche dann prognostische Aussagen zur Lärmbelastung an einem Ort zulassen. Die Darstellungssoftware MetaVIS bietet schließlich die Möglichkeit, eine aktuelle Schallausbreitungssituation analysieren und bewerten zu können. Die Bewertung kann aufgrund einer umfangreichen Datenbibliothek erfolgen. Nach Beendigung des Projektes kann dieses Verfahren vom Auftraggeber zu einer bewerteten ortsabhängigen Schallausbreitungsprognose unter Einbeziehung meteorologischer Parameter genutzt werden. / In this study a method will be specified, which is developed in line of a project work for the Bundeswehr. This method predicts the propagation of shooting noise in particular consideration of the effects of meteorological conditions (weather of sound) and so allows the prediction of increased noise levels. Furthermore, with this method a regional classification of an area like Germany in sound climatologically similarly areas is possible by analysing maps of sound level attenuation for a multiplicity of structure of the atmosphere. Basically the method bases on two parts, a model of sound propagation SMART (Sound propagation model of the atmosphere using ray-tracing) and an application software Meta-VIS (Meteorological attenuation visualization). By means of SMART the attenuation of the sound level will be calculated which approves statements about noise exposure at a certain place. The visualisation software MetaVIS offers finally the chance to analyse and to evaluate a present situation of sound propagation. The estimation can be carried out as a result of a large library of data. Upon completion of the project, the method will be used by the customer to predict the sound propagation dependent on location, namely with inclusion of meteorological parameters.

Die Schallgeschwindigkeit in der Luft hängt wesentlich von der Temperatur, aber auch in gewissen Maße von deren Feuchtigkeit und Zusammensetzung, ab. Den Einfluss der Lufttemperatur auf die Schallgeschwindigkeit nutzen Messverfahren aus, um aus der Laufzeit von Schallsignalen die Temperatur entlang des Ausbreitungsweges zu bestimmen. Dabei wird jedoch häufig die Beeinflussung durch die Luftfeuchte unzureichend berücksichtigt. Hier wird ein Verfahren aufgezeigt, das die Zusammensetzung der Luft und die Temperaturabhängigkeit der spezifischen Wärmen detailliert berücksichtigt. Die auf diesem Wege aus der Schallgeschwindigkeit abgeleitete Temperatur wird mit der in der Mirkometeorologie üblichen Approximation der akustisch virtuellen Temperatur verglichen. / The speed of sound in humid air depends besides the temperature to some degree on their humidity and compositions. Several measuring methods uses the influence of the temperature on speed of sound to calculate from the travel time of acoustic signals the temperature along the propagation path. However, thereby the influence of the humidity is often ignored. This paper described a method, which take the impact of the atmospheric composition and the temperature dependence of the specific heats explicit into account. The subsequent from the speed of sound recalculated temperature is compared with the mircometeorological standard approximation, the acoustic virtual temperature.

The Lattice-Boltzmann-model is analyzed with regard to application to numerical solution of flow acoustic problems. In the first part of this study the description of sound wave propagation by common variants of the Lattice-Boltzmann-model is examined by calculation of phase velocity and effective viscosity for sound waves. Schemes with nine velocities in two dimensions and nineteen velocities in three dimensions are considered. For each of these a single relaxation time model (LBGK-model) and a multiple relaxation time model (MRT) is investigated. All schemes exhibit an almost isotropic error in phase speed of sound waves. With a spatial resolution of 10 or 30 grid spacings per wavelength the deviation of phase speed is less than 1 % or 0.1 %, respectively. The dissipation of sound waves is not simulated correctly by LBGK-models since there the bulk viscosity is fixed to the shear viscosity. Apart from that there is only very little numerical dissipation. The dissipation error therefor is negligible in the audible frequency range in air as long as the simulation volumes do not become very large, i.e. much more than some hundred wavelengths. The MRT-models allow to adjust the bulk viscosity by a suitable choice of relaxation parameters. However, if the bulk viscosity is set to a realistic value, stability of the scheme requires free relaxation parameter values which are close to the relaxation parameters that determine the viscosities. Then the gain in stability of MRT-models compared to LBGK-models is lost to some extent. All schemes considered here are able to reproduce the effect of sound wave convection in homogeneous background flows. Although additional numerical errors arise in transport coefficients, the overall errors are of the same order of magnitude as in the case with zero background flow and are not critical in practical applications. In the second part of the work numerical experiments are described which demonstrate the coupling of the flow- and sound field. Three test cases are considered: Sound generation by a single vortex interaction with the leading edge of a semi-infinite flat plate, sound generation by a grazing flow over a partially covered cavity and instationary flow around a half-cylinder with an attached wedge tail. The first test case is simulated in two dimensions with a self-written program. The sound calculated directly is compared to prediction based on an acoustic analogy. The observed amplitudes of the radiated sound agree quantitatively well for all flow and eddy velocities considered here. This implies, that the coupling of the sound and flow field is correct. In the case of the cavity the flow is computed in two dimensions with a self-written program as well as in three dimensions with the commercially available program PowerFLOW. The simulated pressure fluctuations in the cavity are compared to results of a wind tunnel experiment. Good agreement between simulation and wind tunnel experiment is found. The instationary flow around a half cylinder with an attached wedge tail is simulated in three dimensions using PowerFLOW. The radiated sound cannot be captured with PowerFLOW because of insufficient quantization of fluid density. However, pressure fluctuations on the surface of the body exhibit good agreement with the result of a wind tunnel test. Summarizing the results of this work it can concluded, that the Lattice-Boltzmann-model is well suited to numerical solutions of flow acoustic problems.

No description available.

The Lattice-Boltzmann-model is analyzed with regard to application to numerical solution of flow acoustic problems. In the first part of this study the description of sound wave propagation by common variants of the Lattice-Boltzmann-model is examined by calculation of phase velocity and effective viscosity for sound waves. Schemes with nine velocities in two dimensions and nineteen velocities in three dimensions are considered. For each of these a single relaxation time model (LBGK-model) and a multiple relaxation time model (MRT) is investigated. All schemes exhibit an almost isotropic error in phase speed of sound waves. With a spatial resolution of 10 or 30 grid spacings per wavelength the deviation of phase speed is less than 1 % or 0.1 %, respectively. The dissipation of sound waves is not simulated correctly by LBGK-models since there the bulk viscosity is fixed to the shear viscosity. Apart from that there is only very little numerical dissipation. The dissipation error therefor is negligible in the audible frequency range in air as long as the simulation volumes do not become very large, i.e. much more than some hundred wavelengths. The MRT-models allow to adjust the bulk viscosity by a suitable choice of relaxation parameters. However, if the bulk viscosity is set to a realistic value, stability of the scheme requires free relaxation parameter values which are close to the relaxation parameters that determine the viscosities. Then the gain in stability of MRT-models compared to LBGK-models is lost to some extent. All schemes considered here are able to reproduce the effect of sound wave convection in homogeneous background flows. Although additional numerical errors arise in transport coefficients, the overall errors are of the same order of magnitude as in the case with zero background flow and are not critical in practical applications. In the second part of the work numerical experiments are described which demonstrate the coupling of the flow- and sound field. Three test cases are considered: Sound generation by a single vortex interaction with the leading edge of a semi-infinite flat plate, sound generation by a grazing flow over a partially covered cavity and instationary flow around a half-cylinder with an attached wedge tail. The first test case is simulated in two dimensions with a self-written program. The sound calculated directly is compared to prediction based on an acoustic analogy. The observed amplitudes of the radiated sound agree quantitatively well for all flow and eddy velocities considered here. This implies, that the coupling of the sound and flow field is correct. In the case of the cavity the flow is computed in two dimensions with a self-written program as well as in three dimensions with the commercially available program PowerFLOW. The simulated pressure fluctuations in the cavity are compared to results of a wind tunnel experiment. Good agreement between simulation and wind tunnel experiment is found. The instationary flow around a half cylinder with an attached wedge tail is simulated in three dimensions using PowerFLOW. The radiated sound cannot be captured with PowerFLOW because of insufficient quantization of fluid density. However, pressure fluctuations on the surface of the body exhibit good agreement with the result of a wind tunnel test. Summarizing the results of this work it can concluded, that the Lattice-Boltzmann-model is well suited to numerical solutions of flow acoustic problems.

Negativ empfundene Schallereignisse, d.h. Lärm, sind nach wie vor eines der bedeutendsten Umweltprobleme besonders in urbanen Räumen. Die Ausbreitung von Schallwellen findet, abgesehen von Wechselwirkungen mit dem Boden, in der Atmosphäre statt und wird durch deren Struktur beeinflusst. Eine maßgebliche Rolle spielt dabei die raum-zeitliche Variabilität der meteorologischen Größen Temperatur, Windvektor sowie Luftfeuchtigkeit, die durch Brechung, Streuung und Absorption zu einer verstärkten oder verringerten Schallimmission an einem Ort führen kann. Im Rahmen einer Schülerarbeit (“Besondere Lernleistung”) wurden Schallpegelwerte an mehreren Messpunkten auf dem Gelände des Leipziger Instituts für Meteorologie bei verschiedenen Atmosphärenzuständen aufgenommen. Erste Auswertungen der Messergebnisse werden in dieser Studie vorgestellt. / Noise is one of the most important environmental problems especially in urban regions. The propagation of sound waves takes place in the atmosphere, apart from interactions with the ground surface, and is influenced by the atmospheric structure. Thereby, the spatial and temporal variability of meteorological quantities like temperature, wind vector and air moisture leads to refraction, scattering and absorption and thereupon to an increased or decreased noise exposure. Within the scope of a pupil’s work sound level measurements were carried out on different places at the site of Leipzig Institute of Meteorology during variable atmospheric conditions. First results are presented in this study.

Die internationale Vereinigung der Schall- und audiovisuellen Archive feiert dieses Jahr in Dresden ihr zwanzigjähriges Bestehen. Ziel der rund 400 institutionellen und privaten Mitglieder ist es, das kulturelle Erbe an Tondokumenten und audiovisuellen Medien zu sichern, zu erforschen und der Öffentlichkeit zu vermitteln.

Die internationale Vereinigung der Schall- und audiovisuellen Archive feiert dieses Jahr in Dresden ihr zwanzigjähriges Bestehen. Ziel der rund 400 institutionellen und privaten Mitglieder ist es, das kulturelle Erbe an Tondokumenten und audiovisuellen Medien zu sichern, zu erforschen und der Öffentlichkeit zu vermitteln.

No description available.