Directional filtering of recordings in spherical harmonic domain for auralization of simulated noise barriers

Sammanfattning

The effects of traffic noise on humans can cause significant health problems and canimpair the quality of everyday life. Current research and legal requirements mainlyrefer to physical sound pressure measurements of noise. However, the human perceptionof noise within its acoustic and visual context is not fully considered. Withthe development of growing population that is exposed to noise caused by roads,rails and planes, the need of an evaluation method that includes the perception ofthe noise within its environment gains in importance. At the same time a financiallyefficient tool is needed to reduce costs of construction projects for noise protectionmeasures. Therefore, an evaluation tool should be evolved, that makes it possible toexperience and rate noise protection measures based on a psychoacoustic model invirtual reality. Supported by findings from the virtual reality model, suitable noiseprotection measures can be built in real-life subsequently.The aim of this thesis is to process spatial audio recordings in spherical harmonicsdomain in such a way that the resulting signal contains the spatial sound fieldof the recording including the effects of a synthesized noise barrier. Through this,the auralization of varying noise barriers can be realized for real life scenarios in avirtual environment. The processing is implemented by applying filter functions todirected sectors of a plane wave decomposed form of the signal. The filter functionsapproximate the transfer functions of simple single screen noise barriers, based on asecondary source diffraction calculation model. With this methodology it is possibleto establish directional frequency filtering, which only affects components of thesound field that approach the receiver from certain directions. The model is usedfor filtering complex as well as synthetic generated sound fields and is subsequentlyanalyzed thoroughly. Limitations of the processing are discussed and improvementsare suggested.