Open acoustic measurements for validating edge diffraction simulation methods

Diffraction is a wave phenomenon that is experienced in mostly any daily life situation. Just imagine a walk through a corridor of an office building where sound sources are located in each room. The sound field does not change abruptly when an open door is passed. The transition is rather smooth which comes from sound energy that is bent around the door entrance's edges, i.e. sound diffraction. When a sound wave hits an obstacle, a frequency-dependent shadow zone occurs behind the object (related to the direction of sound propagation). If the object is small in comparison to the wavelength, the incident wave remains unaffected. However, a shadow zone appears and grows clearer and sharper with decreasing wavelength and increasing frequency, respectively. This shadow zone results from a total cancellation of the incident wave by the diffracted wave, which is radiated from the edges or perimeter of the respective object. Thus, sound diffraction must not be neglected in computer simulations, especially in indoor and large-scale urban scenarios. The development of noise barriers is a typical application where computer simulation methods of edge diffraction are taken in account in order to get detailed information about the barrier's efficiency in the respective scenario.