Download Measuring Diffusion in a 2D Digital Waveguide Mesh The digital waveguide mesh is a method by which the propagation of sound waves in an acoustic system can be simulated. An important consideration in modelling such systems is the accurate modelling of reflection characteristics at boundaries and surfaces. A significant property of an acoustic boundary is its diffusivity. In fact partially diffuse sound reflections are observed at most real acoustic surfaces and so this is an important consideration when implementing a digital waveguide mesh model. This paper presents a method for modelling diffusion that offers a high degree of control. The model is implemented with varying amounts of diffusivity, and a method for measuring its diffusive properties is outlined. Results for the model are presented and a method to calculate the diffusion coefficient is described.
Download Hybrid room impulse response synthesis in digital waveguide mesh based room acoustics simulation The digital waveguide mesh (DWM) and related finite difference time domain techniques offer significant promise for room acoustics simulation problems. However high resolution 3-D DWMs of large spaces remain beyond the capabilities of current desktop based computers, due to prohibitively long run-times and large memory requirements. This paper examines how hybrid room impulse response synthesis might be used to better enable virtual environment simulation through the use of otherwise computationally expensive DWM models. This is facilitated through the introduction of the RenderAIR virtual environment simulation system and comparison with both real-world measurements and more established modelling techniques. Results demonstrate good performance against acoustic benchmarks and significant computational savings when a 2-D DWM is used as part of an appropriate hybridization strategy.
Download B-Format Acoustic Impulse Response Measurement and Analysis In the Forest at Koli National Park, Finland Acoustic impulse responses are used for convolution based auralisation and reverberation techniques for a range of applications, such as music production, sound design and virtual reality systems. These impulse responses can be measured in real world environments to provide realistic and natural sounding reverberation effects. Analysis of this data can also provide useful information about the acoustic characteristics of a particular space. Currently, impulse responses recorded in outdoor conditions are not widely available for surround sound auralisation and research purposes. This work presents results from a recent acoustic survey of measurements at three locations in the snow covered forest of Koli National Park in Finland during early spring. Acoustic impulse responses were measured using a B-format Soundfield microphone and a single loudspeaker. The results are analysed in terms of reverberation and spatial characteristics. The work is part of a larger study to collect and investigate acoustic impulse responses from a variety of outdoor locations under different climatic conditions.