About Noise Simulation Laboratory
Realistic Audiovisual Recording, Simulation, and Reproduction of Traffic Noise and Noise Abatement Measures
When it comes to planning transport infrastructure and noise abatement measures different complex physical phenomena are an issue. Yet only a relatively small group of experts fully understands the complex connections of these phenomena. The abstract calculations and visualizations used in planning are only partially suitable for conveying these connections to decision-makers in the economic, political and social sector.
Until now, an interface between the fields of calculation/simulation on the one hand and the intuitive experienceable, realistic audiovisual depiction of rail traffic noise and urban development effects of noise mitigation methods, on the other hand, was missing.
In cooperation with the DB AG, an innovative technology was developed and implemented in the TiME Lab of the Fraunhofer Heinrich Hertz Institute HHI in Berlin. Based on spatial sound recordings and acoustic simulations in combination with high-resolution video panoramas or photorealistic 3D computer graphics, the noise simulation “Info Point Noise Protection” (Infopunkt Lärmschutz”) was developed.
With the help of a 12 meters wide 180 degrees panoramic projection and a 3D audio reproduction system based on wave-field synthesis, simulations of railroad traffic noise can be reproduced realistically in an unprecedented quality at the TiME Lab. Furthermore, various noise reduction or urban development measures can be integrated into the audiovisual simulation. As a result, the visitor finds himself in the center of a virtual space – for instance directly in front of a planned railway section. He is able to experience the future structural and acoustic situation as well as the efficiency of the planned noise reduction measures in a realistic manner.
In addition to the representation in the TiME Lab, a simpler mobile version of the simulator was developed. This makes the system very user-friendly. Hence, the system can, for instance, be used in meetings with representatives of local citizens’ initiatives to demonstrate realistic scenarios of the planned noise reduction measures on site.
Published with the kind permission of Deutschen Bahn AG. You can watch the video here.
SOUND RECORDING FOR REALISTIC SOUND FIELD REPRODUCTION
Special microphone systems are used for audio recording. A 3D microphone array with 14 microphones allows the correct level and localization for the sound field reproduction using the wave field synthesis system in the TiME Lab. Furthermore, an artificial head microphone system is used for later headphone reproduction, for example as part of the interactive mobile demonstrator.
ACOUSTIC SIMULATION OF NOISE REDUCTION MEASURES
Based on the original sound recordings, various conventional and innovative noise reduction measures such as noise barriers, rail dampers or rail web shields can be simulated. By making these simulations audible and experienceable, they can be compared with each other. The noise reduction measures have not only the correct level but can also be spectrally simulated for the selected listening position.
PROCESSING AND PROGRAMMING FOR THE INTERACTIVE DEMONSTRATOR
In addition to the representation in the TiME Lab, a simplified, mobile version of the simulator has been developed. The viewer can choose and compare different scenarios via a touchscreen interface. The passing trains are displayed in real time on a HD display (1920 x 1080 pixels, with 50 frames per second).
For a realistic audio reproduction, a two-channel audio format optimized for headphone playback is used. By means of this binaural method, there is no 'in-head localization' of the sound event – in contrast to the headphone reproduction of conventional stereophonic signals. The listeners perceive the passing trains frontally and from the right direction. The headphone systems are also calibrated to the correct reproduction level.