![]() ![]() To account for edge diffraction, several exact and asymptotic solutions in the frequency and time domain exist. Keller (1962) coined the concept of edge diffracted rays in the geometrical theory of diffraction (GTD), considering the incident and reflected diffracted field at straight and curved edges. The uniform theory of diffraction (UTD Kouyoumjian and Pathak, 1974) has been established as an asymptotic high-frequency solution for diffraction of electromagnetic waves and similar solutions for acoustic diffraction have been derived (e.g., Pierce, 1974). An exact time-domain solution was suggested by Biot and Tolstoy (1957) and extended by Medwin (1981) and Svensson et al. A reformulation in the frequency domain was presented in Svensson et al. (2009) use line integrals along the physical edge based on the concept of secondary sources located along the edge, particularly suited for handling finite edges. Several approximations have been suggested, e.g., using empirically based simplifications ( Maekawa, 1968), for the required Fresnel terms in UTD ( Kawai, 1981), for the secondary source model (e.g., Calamia and Svensson, 2006) in the context of a directive line source model (e.g., Menounou and Nikolaou, 2017), or for half-planes ( Ouis, 2019). With considerable computation time spent on diffraction path finding, existing approximations for VAEs typically use filters derived by evaluating diffraction solutions at relatively low spectral resolution and restriction to infinite wedges in the shadow zone (e.g., Schissler et al., 2021) or from a coarse approximation of prototypical object shapes (e.g., Pisha et al., 2020). Parametric filter approximations of diffraction have been optimized in Pulkki and Svensson (2019) using machine learning, and have been heuristically derived using geometric parameters for a diffraction lowpass filter in Kirsch and Ewert (2021), also with restrictions to the shadow zone. Here, a unified filter representation of the singly diffracted sound field by an arbitrary wedge is suggested. I think you should only use this option if you don't need reflections (ie: if you're just using Steam Audio to get the binaural effect).Wedge diffraction is described as superposition of (up to four) fractional half-order lowpass filters, representing the diffracted incident and reflected sound field. NOTE: In my testing, I found that the setup described in option 2 will severely mess with Phonon's reflection system. If you need to use an unrealistic falloff curve, then use option 2 above and customise the falloff curve with Unity's Audio Source. OPTION 2 - If you want to have the 'Spatial Blend' set to 1 (ie: 3D) on the Unity Audio Source, then you must uncheck 'Physics Based Attenuation' on the Phonon Effect script.įurthermore, Phonon's physics based attenuation is not customisable.OPTION 1 - If you want to have 'Physics Based Attenuation' checked on the Phonon Effect script, then you must set the 'Spatial Blend' to 0 (ie: 2D) on the Unity Audio Source.To avoid applying distance attenuation multiple times, either uncheck Physics Based Attenuation in Phonon Effect or ensure that no distance attenuation is applied by the Audio Source. Physics-based attenuation is applied on top of any distance attenuation specified in the 3D Sound Settings of an Audio Source in Unity. Originally posted by MDA Digital AB:grenade explosions and fire arm sounds just disperse way too fast.In the manual, it says the following on page 6 under the heading "Physics Based Attenuation": A value of 0.5 will cause and occluded sound to be rendered at half the volume that it would otherwise be rendered at if it was not occluded.A value of 0 will effectively nullify the occlusion effect even when it's enabled.The default setting of 1 will produce the same behaviour as we currently see.This setting can have a value between 0 and 1.This implies that each air particle is a sound. Rather, the sound waves of the radio cause longitudinal vibrations in the air in the entryway. The music from the radio can be audible directly in front of the entrance without diffraction. ![]() Diffraction occurs in all waves, not only sound waves. In the event that that feature won't be implemented, I had an idea for a simplistic stopgap solution to reduce the harshness of occlusion:Īdd a new parameter to the 'Phonon Effect' script (or where ever it's appropriate) called: Diffraction is the term for the bending of a wave. Will that feature be coming to Steam Audio? What happened to the diffraction simulation that was shown in the first half of the following demo video from 2015? Diffraction is a wave characteristic and occurs for all types of waves. The bending of a wave around the edges of an opening or an obstacle is called diffraction. In real life, sound doesn't get so aggressively muffled if you hide behind a pillar. If we pass light through smaller openings, often called slits, we can use Huygens’s principle to see that light bends as sound does (see Figure 27.9 ). (The video is fairly quiet so turn your volume up. Here is a video demonstration of the issue I'm describing. ![]()
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