Zur Detektierbarkeit der Geräusche einer Windenergieanlage unter verschiedenen meteorologischen Bedingungen

Akustische Langzeitmessungen im Umfeld einer WEA zeigen den typischen Tagesgang des hörbaren Schalls auch in entfernteren Positionen zur WEA. Dieser ist geprägt von Umgebungsgeräuschen wie Vogelgezwitscher, Hundegebell und Blätterrauschen und dem in Bodennähe aufkommenden Wind. Das Schallsignal der WEA ist im Ein-Minuten-Ausschnitt innerhalb von einigen Terzbändern erkennbar. Dort sind periodische Signale sichtbar, woraus sich das Signal des 3-Blatt-Rotors mit seiner Umdrehungsfrequenz mittels einer FFT bestimmen lässt. Die Abhängigkeit vom Wetter, wie atmosphärischer Schichtung, und Windgeschwindigkeit wird durch eine Zusammenfassung der FFT-Ergebnisse in Tagesgänge gezeigt

2000 land-use regressions for road traffic noise predictions – how sample selection affects extrapolation weights

The awareness that noise exposure is critical for human health is growing around the globe, and land-use regressions (LURs) are becoming a popular tool for producing noise exposure maps. One important factor for noise emissions is road traffic. The propagation in this regard is determined by the spatial layout of road infrastructure and the surrounding environment, respectively. LURs use geostatistical models and allow to extrapolate microphone measurements. In this study, we investigated whether models are prone to sampling artifacts. We used yearly averaged Lden simulations, compliant to the European noise directive 2002/49/EG, as input for 2000 virtual field campaigns. We permuted different sampling schemes (random, systematic, stratified) and sizes (n = 50, 100, 200, 500 to 1000) 100 times. The overall model performances varied substantially between 0.61 – 0.95 for R², 1.94 – 7.46 dB(A) for mean absolute error and 2.47 – 10.03 dB(A) for root mean squared error. Comparing the eventual model terms using variance analyses (ANOVA), we found significant differences between the sampling schemes for traffic information and land cover (e.g. vegetated surfaces) features. Simultaneously, less than half of the LURs’ weights differed significantly depending on the sampling size. Thus, our experiments give an in-depth view on the mechanics of LUR and their sensitivity with respect to sampled training data

Acoustic effects of a tree simulated by a FDTD model

Trees and forests as a natural noise barrier would be an eco-friendly solution for noise reduction, as they have additional positive effect for air quality too. To quantify the sound attenuation by trees, the simulation of sound propagation in and around forest areas requires a detailed understanding of the acoustic properties of single trees. Therefore the acoustic effects of different trees are investigated by means of a three-dimensional finite difference time domain (FDTD) sound propagation model within a frequency range from 50 to 1500 Hz. The choice of the model type instantaneously enables the consideration of multiple reflection and diffraction. The influence of trunk size, branch density and the shape of the tree on backscattering and transmission is studied. The spatial resolution in this case is 5 cm. The acoustic properties of real and idealized trees are compared and presented to attain a classification for the typical tree parameters. As earlier studies have shown the main effect results from the diameter of the trunk. Another important parameter is the density of branches within a volume. This is described by the partial volume and the partial cross section. The long-term objective of this study is to gain a new parameterization for a realistic implementation of canopy in sound propagation models

Railway noise annoyance: Exposure-response relationships and testing a theoretical model by structural equation analysis

In some regions the exposure to railway noise is extremely concentrated, which may lead to high residential annoyance. Nonacoustical factors contribute to these reactions, but there is limited evidence on the interrelations between the nonacoustical factors that influence railway noise annoyance. The aims of the present study were (1) to examine exposure-response relationships between long-term railway noise exposure and annoyance in a region severely affected by railway noise and (2) to determine a priori proposed interrelations between nonacoustical factors by structural equation analysis. Residents (n = 320) living close to railway tracks in the Middle Rhine Valley completed a socioacoustic survey. Individual noise exposure levels were calculated by an acoustical simulation model for this area. The derived exposure-response relationships indicated considerably higher annoyance at the same noise exposure level than would have been predicted by the European Union standard curve, particularly for the night-time period. In the structural equation analysis, 72% of the variance in noise annoyance was explained by the noise exposure (Lden) and nonacoustical variables. The model provides insights into several causal mechanisms underlying the formation of railway noise annoyance considering indirect and reciprocal effects. The concern about harmful effects of railway noise and railway traffic, the perceived control and coping capacity, and the individual noise sensitivity were the most important factors that influence noise annoyance. All effects of the nonacoustical factors on annoyance were mediated by the perceived control and coping capacity and additionally proposed indirect effects of the theoretical model were supported by the data

Schallausbreitung in der Atmosphäre

Die Abhängigkeit der Schallausbreitung von den atmosphärischen Bedingungen (also vom Wetter) kann jeder feststellen, der mal genau in seine Umwelt hineinhört. Die physikalischen Prozesse, die dabei eine wichtige Rolle spielen, wie Dämpfung, Brechung, Streuung, Beugung und Reflexion von Schallwellen sowie deren Nachbildung mit einem Schallausbreitungsmodell werden vorgestellt. Speziell werden Bodendämpfungseffekte und deren Realisierung in einem Modell erläutert

My Work at the German Aerospace Center

Überblick meiner Tätigkeit als Gastwissenschaftler. Modell und Satelliten Datenanalyse und Vergleich bezgl. LNOX

München, Sonneninsel im Nebelmeer. Was vertreibt den Nebel in der Stadt?

Die Stadt als Wärmeinsel wird unter bestimmten Bedingungen auf Satellitenbildern sichtbar. Durch die Kenntnis der Temperaturschichtung kann auf die Wärmeenergiemenge geschlossen werden, die an die Umwelt abgegeben wird

Meteorological effects on the 3D sound propagation inside an inhomogeneous forest area

Der Einfluss von Wald auf die Schallausbreitung wird in einem Waldstück mit einer Lichtung untersucht. Dabei werden die Unterschiede der meteorologischen Parameter im Wald und in der Lichtung in Modellsimulationen beachtet. Simulationsergebnisse und Messergebnisse werden verglichen

On the detectability of a wind turbines noise under different meteorological conditions

Langzeitmessungen zur Überwachung der Lärmimmission von Windenergieanlagen verlangen eine Zuordnung der Geräusche zu der Quelle. Es werden verschiedene meteorologische Bedingungen gegenübergestellt und die Einflüsse des Wetters auf die Detektierbarkeit der WEA-Geräusche dargestellt