Download Hyper-Dimensional Digital Waveguide Mesh for Reverberation Modeling Characteristics of digital waveguide meshes with more than three physical dimensions are studied. Especially, the properties of a 4-D mesh are analyzed and compared to waveguide structures of lower dimensionalities. The hypermesh produces a response with a dense and irregular modal pattern at high frequencies, which is beneficial in modeling the reverberation of rooms or musical instrument bodies. In addition, it offers a high degree of decorrelation between output points selected at different locations, which is advantageous for multi-channel reverberation. The frequencydependent decay of the hypermesh response can be controlled using boundary filters introduced recently by one of the authors. Several hypermeshes can be effectively combined in a multirate system, in which each mesh produces reverberation on a finite frequency band. The paper presents two hypermesh application examples: the modeling of the impulse response of a lecture hall and the simulation of the response of a clavichord soundbox.
Download Real-Time 3D Finite-Difference Time-Domain Simulation of Low- and Mid-Frequency Room Acoustics Modern graphics processing units (GPUs) are massively parallel computing environments. They make it possible to run certain tasks orders of magnitude faster than what is possible with a central processing unit (CPU). One such case is simulation of room acoustics with wave-based modeling techniques. In this paper we show that it is possible to run room acoustic simulations with a finite-difference time-domain model in real-time for a modest-size geometry up to 7kHz sampling rate. For a 10% maximum dispersion error limit this means that our system can be used for realtime auralization up to 1.5kHz. In addition, the system is able to handle several simultaneous sound sources and a moving listener with no additional cost. The results of this study include performance comparison of different schemes showing that the interpolated wideband scheme is able to handle in real-time 1.4 times the bandwidth of the standard rectilinear scheme with the same maximum dispersion error.
Download Spatial High Frequency Extrapolation Method for Room Acoustic Auralization Auralization of numerically modeled impulse responses can be informative when assessing the geometric characteristics of a room. Wave-based acoustic modeling methods are suitable for approximating low frequency wave propagation. Subsequent auralizations are perceived unnaturally due to the limited bandwidth involved. The paper presents a post-processing framework for extending low-mid frequency band limited spatial room impulse responses (SRIR) to include higher frequency signal components without the use of geometric modeling methods. Acoustic parameters for extrapolated RIRs are compared with reference measurement data for existing venues and a Finite Difference Time Domain modeled SRIR is extrapolated to produce a natural sounding full-band SRIR signal. The method shows promising agreement particularly for large venues as the air absorption is more dominant than the boundary absorption at high frequencies.