Karl Bolin

Infrasound and low frequency noise from wind turbines: exposure and health effects

Wind turbines emit low frequency noise (LFN) and large turbines generally generate more LFN than small turbines. The dominant source of LFN is the interaction between incoming turbulence and the blades. Measurements suggest that indoor levels of LFN in dwellings typically are within recommended guideline values, provided that the outdoor level does not exceed corresponding guidelines for facade exposure. Three cross-sectional questionnaire studies show that annoyance from wind turbine noise is related to the immission level, but several explanations other than low frequency noise are probable. A statistically significant association between noise levels and self-reported sleep disturbance was found in two of the three studies. It has been suggested that LFN from wind turbines causes other, and more serious, health problems, but empirical support for these claims is lacking.

Auditory masking of wanted and unwanted sounds in a city park

Auditory masking of unwanted sounds by wanted sounds has been suggested as a tool for outdoor acoustic design. Anecdotal evidence exists for successful applications, for instance the use of fountai ...

The Potential of Natural Sounds to Mask Wind Turbine Noise

Wind turbine (WT) noise may cause annoyance, especially in relatively quiet areas with low ambient levels. As a compliment to conventional noise control at the source, addition of wanted sounds may ...

Long range sound propagation over a sea surface

This paper describes methodology and results from a model-based analysis of data on sound transmission from controlled sound sources at sea to a 10-km distant shore. The data consist of registrations of sound transmission loss together with concurrently collected atmospheric data at the source and receiver locations. The purpose of the analysis is to assess the accuracy of methods for transmission loss prediction in which detailed data on the local geography and atmospheric conditions are used for computation of the sound field. The results indicate that such sound propagation predictions are accurate and reproduce observed variations in the sound level as function of time in a realistic way. The results further illustrate that the atmospheric model must include a description of turbulence effects to ensure predicted noise levels to remain realistically high during periods of sound shadow.

Prediction Method for Wind-Induced Vegetation Noise

This article examines the sound generated when the wind interacts with vegetation. A wind field model has been coupled to a new method for predicting sound from vegetation. This includes prediction ...

The influence of background sounds on loudness and annoyance of wind turbine noise

Natural sounds may create pleasant soundscapes that mask wind turbine noise. To explore this, a listening test was performed to investigate the influence of background sounds on perceived loudness ...

Air-borne sound generated by sea waves

This paper describes a semi-empiric model and measurements of air-borne sound generated by breaking sea waves. Measurements have been performed at the Baltic Sea. Shores with different slopes and sediment types have been investigated. Results showed that the sound pressure level increased from 60 dB at 0.4 m wave height to 78 dB at 2.0 m wave height. The 1/3 octave spectrum was dependent on the surf type. A scaling model based on the dissipated wave power and a surf similarity parameter is proposed and compared to measurements. The predictions show satisfactory agreement to the measurements.

Long term estimations of low frequency noise levels over water from an off-shore wind farm.

This article focuses on computations of low frequency sound propagation from an off-shore wind farm. Two different methods for sound propagation calculations are combined with meteorological data for every 3 hours in the year 2010 to examine the varying noise levels at a reception point at 13 km distance. It is shown that sound propagation conditions play a vital role in the noise impact from the off-shore wind farm and ordinary assessment methods can become inaccurate at longer propagation distances over water. Therefore, this paper suggests that methodologies to calculate noise immission with realistic sound speed profiles need to be combined with meteorological data over extended time periods to evaluate the impact of low frequency noise from modern off-shore wind farms.

Listening Test Comparing A-Weighted and C-Weighted Sound Pressure Level as Indicator of Wind Turbine Noise Annoyance

A listening test was conducted to investigate whether A-or C-weighed sound levels are most suitable as indicator of annoyance due to wind turbine noise. The tests consisted of fifteen different win ...

Detached-Eddy Simulation of a Horizontal Axis Wind Turbine

Aerodynamic simulations of a small horizontal-axis wind turbine, suitable for integration of wind energy in urban and peri-urban areas, are performed using the improved delayed detached-eddy simulation method. Simulations are carried out for three rotation rates and inlet conditions. Aerodynamic characteristics of the wind turbine such as forces, power production, pressure distribution as well as flow topologies are presented. The effect of different rotation rates as well as the effect of free stream turbulence on the turbine aerodynamics are discussed.