The basic thought of the project is to prevent the manifestation of prejudices and resistances towards wind turbines early on. For instance, if a wind farm was to be built near Hamburg, it is easy to imagine that there will be citizens who are sceptical of this proposal because they fear noise pollution or landscape disfigurement.

The phenomenon is appropriately named “not in my backyard”. This is where the X-Eptance-Explore project comes in, providing 3D visualization and auralization of wind turbines. Auralization is a method of making acoustic situations artificially audible.

X-Eptance-Explore uses virtual reality (VR) and, in a further step, augmented reality (AR) to simulate the realistic landscape in which the wind turbine will be built. Geo-referenced data and a three-dimensional sound field are used to create a holistic, true-to-life image of an environment that can be experienced by citizens, says project team member Iwer Petersen from the Competence Center for Renewable Energies and Energy Efficiency (CC4E) at the HAW Hamburg.

The aim is to create the feeling that you are really there, although in reality you are standing in a different room. Using a game engine, a development program fed with data from Open Street Maps and other sources, a comprehensive image of the surroundings is generated.

Matching acoustics for every weather condition

Critics claim that it is too difficult to capture all the parameters of a wind turbine and the surrounding landscape and to reproduce them. Besides, surely a wind turbine sounds different when it is raining or you are standing exactly in the wind direction? The HAW Hamburg has dealt with these obstacles, too, and has recorded a variety of acoustically relevant parameters.

Virtual reality means a digital, artificial world that can be experienced via special software and hardware. Virtual reality uses 3D graphics generation technologies and multi-sensor interaction technologies. By using VR glasses with high-resolution displays, the user is able to immerse themselves completely in the virtual world via 360° or 3D content and auditory elements.

These parameters include the position of the sun, humidity, wind strength, air pressure, temperature, and the distance to a wind turbine. “Thus, we want to create acoustics that are as realistic as possible,” says project leader Prof. Dr. Birgit Wendholt. Moreover, the researchers can generate ambient sounds based on plants, trees, or roads within a radius of two kilometres

All of these parameters can cause the soundscape to change and the turning of a wind turbine's rotors to be perceived differently. Thus, the sound varies depending on the environment. The X-Eptance-Explore project relies on systematization to approach this problem, attempting to record and categorize sounds and sound propagation effects and thus assign them to individual sources. Sounds can then be superimposed to create a sound image that takes various influences into account.

Creating virtual wind farms at any desired location

“Our goal was to create a three-dimensional sound field in which users can move freely in virtual reality to assess the virtual wind farm from any location,” says the project manager. However, the technical equipment is crucial to the success of this project. In addition to the virtual reality equipment, a modern audio engine is used in which sound sources and acoustic propagation effects are modelled based on the obtained parameters. The long-term goal of this project is to automate the procedures and findings to the point where a virtual wind farm can be created at any location.

But as is often the case in research, unforeseen developments have slowed down and changed the project. Originally, the project team wanted to make wind turbines not only experienceable through virtual reality (VR) but to enable the experience via augmented reality (AR), too. The advantage of AR is that it does not replace reality but extends it. People can move freely in space and touch objects.

However, this kind of representation requires a convincing mix of virtual content with the real world. This already works well for visual perceptions but only rudimentarily for acoustic ones. Due to technical and systemic differences in the project and the fact that headphones for mixing virtual and real sounds are still in their infancy, this project step had to be put on hold for now. Nevertheless, the team was able to make good use of its time by further perfecting the VR technology.

Better access for everyone is a long-term goal

The predecessor project X-Eptance-Impulse had already created basic data and video recordings in 360-degree format, which served as a basis for the VR version and were steadily improved. All measurements were based at the Curslack wind farm in Hamburg where numerous calibration and validation tests were carried out during the course of the project.

For instance, the team initiated soundwalks in which individual test persons walked a predefined route to gain an impression of the different sounds in a specific area. In addition, the soundscape was recorded and later played back to interested listeners via headphones in order to point out potential differences and to improve the technique. Thus, the team was able to ensure that the sounds were reconstructed as accurately as possible. The resulting system both visually and audibly recreates a wind turbine in an existing landscape that can be experienced as realistically as possible.

In a follow-up project called Open Citizen Soundwalks (OCSW), the team is now examining how to make the virtual wind farm more accessible, since many people do not have access to the necessary VR hardware yet. Furthermore, the HAW Hamburg is trying to automate the process of creating a virtual audio-visual wind farm in order to soon be able to present projected wind farms directly “in my backyard”.