Titel: Sound propagation around off-shore wind turbines: Long-Range Parabolic Equation
Calculations for Baltic Sea Conditions
Författare: Lisa Johansson
Utgivare: Kungliga Tekniska Högskolan, Stockholm
Årtal: 2003
Ämnesord: Ljud
Sökord/Keyword: wind turbine noise, off-shore wind power, long-range sound propagation,
parabolic equation, scattering, water waves
Avhandling (Pdf)
Sammanfattning: Low-frequency, long-range sound propagation over a sea surface has been calculated using a wide-angel Cranck-Nicholson Parabolic Equation method. The model is developed to investigate noise from off-shore wind turbines. The calculations are made using normal meteorological conditions of the Baltic Sea. Special consideration has been made to a wind phenomenon called low level jet with strong winds on rather low altitude.
The effects of water waves on sound propagation have been incorporated in the ground boundary condition using a boss model. This way of including roughness in sound propagation models is valid for water wave heights that are small compared to the wave length of the sound. Nevertheless, since only low frequency sound is considered, waves up to the mean wave height of the Baltic Sea can be included in this manner.
The calculation model has been tested against benchmark cases and agrees well with measurements. The calculations show that channelling of sound occurs at downwind conditions and that the sound propagation tends towards cylindrical spreading. The effects of the water waves are found to be fairly small.