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3D audio spatializers for Virtual Reality (VR) can use the acoustic properties of the surfaces of a visualised game space to calculate a matching reverb. However, this approach could lead to reverbs that impair the tasks performed in such a space, such as listening to speech-based audio. Sound designers would then have to alter the room's acoustic properties independently of its visualisation to improve speech intelligibility, causing audio-visual incongruency. As user expectation of simulated room acoustics regarding speech intelligibility in VR has not been studied, this study asked participants to rate the congruency of reverbs and their visualisations in 6-DoF VR while listening to speech-based audio. The participants compared unaltered, matching reverbs with sound-designed, mismatching reverbs. The latter feature improved D50s and reduced RT60s at the cost of lower audio-visual congruency. Results suggest participants preferred improved reverbs only when the unaltered reverbs had comparatively low D50s or excessive ringing. Otherwise, too dry or too reverberant reverbs were disliked. The range of expected RT60s depended on the surface visualisation. Differences in timbre between the reverbs may not affect preferences as strongly as shorter RT60s. Therefore, sound designers can intervene and prioritise speech intelligibility over audio-visual congruency in acoustically challenging game spaces. [ABSTRACT FROM AUTHOR]

3D time-domain acoustic modeling techniques have the potential to produce more accurate simulation of the vocal tract than previously implemented 1D or 2D solutions, although the variability of human voice renders it a problematic benchmark for validation of its resynthesis. This study uses acoustic measurement of acrylic cylindrical vocal tract models derived from X-Ray data to assess the validity of comparable 3D digital waveguide mesh simulations. It is found that for more simple structures the 3D digital waveguide mesh is able to reproduce the acoustic behavior up to 10 kHz with only slight errors in resonant frequencies. As the simulated structures become more geometrically complex, this shifting becomes more severe. [ABSTRACT FROM PUBLISHER]

A single room impulse response can reveal information about the acoustics of a given space in both objective, and, when used for auralization, subjective terms. However, for additional spatial information, or more accurate and perceptually convincing auralization, multiple impulse responses are needed. Higher order Ambisonics is a robust means of capturing the spatial qualities of an acoustic space over multiple channels for decoding and rendering over many possible speaker layouts. A method for obtaining Nth-order Ambisonic impulse responses from a room acoustic model, based on lower orders using differential microphone techniques is presented. This is tested using a third-order encoding of a 2-D finite difference time domain room acoustic simulation based on multiple circular arrays of receivers. Accurate channel directional profiles are obtained and results are verified in a series of listening tests comparing the localization of a sound source placed within the given simulation to the same source encoded directly. This generic encoding scheme can be applied to any room acoustic simulation technique where it is possible to obtain impulse responses across multiple receiver positions. Although the proposed method encompasses horizontal encoding only, it can also be applied directly in 3-D simulations where height information is not required in the final auralization. [ABSTRACT FROM PUBLISHER]

The digital waveguide mesh can be used to simulate the propagation of sound waves in an acoustic system. The accurate simulation of the acoustic characteristics of boundaries within such a system is an important part of the model. One significant property of an acoustic boundary is its diffusivity. Previous approaches to simulating diffuse boundaries in a digital waveguide mesh are effective but exhibit limitations and have not been analyzed in detail. An improved technique is presented here that simulates diffusion at boundaries and offers a high degree of control and consistency. This technique works by rotating wavefronts as they pass through a special diffusing layer adjacent to the boundary. The waves are rotated randomly according to a chosen probability function and the model is lossless. This diffusion model is analyzed in detail, and its diffusivity is quantified in the form of frequency dependent diffusion coefficients. The approach used to measuring boundary diffusion is described here in detail for the 2-D digital waveguide mesh and can readily be extended for the 3-D case. The Modeling of Diffuse Boundaries in the 2-D Digital Waveguide Mesh. [ABSTRACT FROM AUTHOR]