Entwicklung einer mit Messungen validierten Modellkette zur Simulation meteorologischer Effekte auf die Schallausbreitung in Waldgebieten
Final Report Abstract
Noise is one of the strongest environmental problems of modern industrialized nations. It has become increasingly important for the health and wellbeing of the population. The influence of forests on sound propagation is currently discussed to reduce the noise exposure. Particular attention must be paid to the meteorological influence, which can lead to acoustic channelling effects in forest areas. Previous investigations provide a mixed picture of sound attenuation within forested areas, especially for the temporally and spatially variable meteorological influence. The main objective of the project is therefore to quantify meteorological effects in the sound propagation through inhomogeneous forests. Thus, a validated model chain of atmospheric and acoustic models was developed and adapted to several meteorological and vegetation-specific conditions. The highly resolved atmospheric boundary layer model HIRVAC2D (High Resolution Vegetation Atmosphere Coupler) is used for the meteorological simulations in forests, forest strips and on forest clearings. The modification of temperature and wind fields due to forests leads to a modified sound propagation compared to conditions at grassland sites. Therefore, the simulated temperature and wind fields are used as meteorological input data for different sound propagation models (SMART: Sound propagation Model of the Atmosphere using Ray-Tracing and a model based on Crank-Nicholson Parabolic Equation). Using this model chain, the meteorological influence on sound propagation for various forest areas (150 m wide deciduous and coniferous forest strips, 100 m wide clearing within inhomogeneous forest) and for different thermal stratifications and wind profiles (depending on daytime and season) is illustrated. Several look-up tables of the meteorological excess attenuation result for 64 situations, e.g. for direct applications without further computational efforts. The meteorologically related sound attenuation reaches, particularly for higher sound frequencies, values that are in the range of measured and modelled total attenuation for a forest strip. The simulations are also adapted to measurement campaigns that were carried out each year since 2011 in Tharandt forest (near Dresden, Germany). Thereby, five synchronized microphones along sound paths of up to 200 m length measured the sound propagation of artificial signals during day- and nighttime. Beside the acoustic measurements, the meteorological conditions were investigated using ultrasonic anemometers at masts up to a height of 40 m. In this way, a model chain, verified with measurements, is formed that is used for different vegetation scenarios, times and seasons. The results of model simulations and measurements confirm the significant meteorological influence on the propagation of sound already over short distances of some 10 m. The sound propagation in downwind direction is of special interest for noise protection applications. The investigated deciduous forest strip provides the maximal meteorological excess attenuation (up to 16 dB/100 m for 1000 Hz) in comparison to grassland, caused by the meteorologically related sound refraction. Thereby, the simulated daily variability of the excess attenuation due to forest meteorology amounts to a standard deviation of the daily mean of 1-9 dB. These studies enable improved parameterization of forest influence on noise immission depending on meteorological and vegetation specific constraints that allows an application in standardized sound propagation models.
Publications
- 2012: Messung und Modellierung meteorologischer Effekte auf die Schallausbreitung im Tharandter Wald. METTOOLSVIII, Leipzig, Wiss. Mitt. Inst. f. Meteorol. Univ. Leipzig, Band 49, ISBN 978-3-9811114-9-1
Ziemann, A., Hehn, M., Barth, M.
- 2012: Meteorological effects on the sound propagation through forests – Measurements and numerical simulations. EURONOISE, Prague, Czech Republic, European Acoustics Association, ISBN 978-80-01-05013-2 (publ. on CD-ROM)
Ziemann, A., Hehn, M., Barth, M.
- 2013: Experimental investigation of the meteorologically influenced sound propagation through an inhomogeneous forest site. Meteorol. Z. 22(2), 221-229
Ziemann, A., Barth, M., Hehn, M.
(See online at https://doi.org/10.1127/0941-2948/2013/0387) - 2013: Modeling meteorological influences on the sound propagation through forest areas. AIA-DAGA, Merano, Italy, Deutsche Gesellschaft für Akustik e.V., ISBN 978-3- 939296-05-8 (publ. on CD-ROM)
Ziemann, A., Fischer, G., Goldberg, V.
- 2014: Meteorological influences on the noise reduction potential of forests. DAGA, Oldenburg, Deutsche Gesellschaft für Akustik e.V., ISBN 978-3-939296-06-5 (publ. on CD-ROM)
Ziemann, A., Wilson, D.K.
- Meteorological effects on the 3D sound propagation inside an inhomogeneous forest area. Meteorol. Z. Meteorologische Zeitschrift, Vol. 25, No. 3, 327–339
Ziemann, A., Schady, A., Heimann, D.
(See online at https://doi.org/10.1127/metz/2016/0710)
