ROOM RESONANCES USING WAVE BASED GEOMETRICAL ACOUSTICS (WBGA (original) (raw)
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Room Resonances Using Wave Based Geometrical Acoustics
Geometrical acoustics, using plane wave propagation and sound absorption coefficients, fail to calculate room resonances. Usually such wave phenomena are being calculated with numerical methods such as Finite Element Method or similar which are computationally heavy. The WBGA, which is based on the image source method, spherical wave propagation, impedance discontinu-ities and sound pressure summation, can accurately simulate room resonances both in the frequency and spatial domain. In this paper we present calculation results of room resonances using the WBGA compared to published data.
Until recently geometrical acoustics has been considered an approximate method of calculating the sound field within a 3D environment because of certain limitations in existing methods. Geometrical acoustics mostly refers to the use of ray tracing and image sources. Ray tracing is a pure energetic method, while the image source method, despite calculating complex sound pressures and theoretically representing a solution to the wave equation, has certain limitations. One of the limitations found in most of the image source implementations is the use of plane wave reflection coefficient and absorption coefficients, a fact that prohibited image sources to be an exact solution of the wave equation. In this paper we extend the image source method, using spherical wave reflection and diffraction coefficients as well as complex surface impedance. We compare the results of the calculations with published data and we conclude that the use of spherical wave coefficients and complex impedance can improve room acoustics predictions.
THE SEAT DIP EFFECT USING WAVE BASED GEOMETRICAL ACOUSTICS (WBGA
The seat dip effect is considered to be one of the intractable acoustical phenomena in room acous-tical simulations. This phenomenon is mainly due to edge sound diffraction and scattering. Wave Based Geometrical Acoustics (WBGA), which originates from the image source method, spherical wave propagation, impedance discontinuities and sound pressure summation, accounts for wave phenomena such as reflection from planes, diffraction from edges, refraction due to strati-fication of mediums to mention a few. By applying WBGA, we demonstrate that the seat dip effect can be accurately calculated and predicted. This paper compares results of the seat dip effect calculated using WBGA with published and measured data.