Download Scalable Spectral Reflections In Conic Sections The object of this project is to present a novel digital audio effect based on a real-time, windowed block-based FFT and inverse FFT. The effect is achieved by mirroring the spectrum, producing a sound effect ranging from a purer rendition of the original, through a rougher one, to a sound unrecognisable from the original. A mirror taking the shape of a conic section is constructed between certain partials, and the modified spectrum is created by reflecting the original spectrum in this mirror. The user can select the type and continuously vary the amount of curvature, typically ‘roughening’ the input sound quite gratifyingly. We demonstrate the system with live real-time audio via microphone.
Download RoomWeaver: A Digital Waveguide Mesh Based Room Acoustics Research Tool RoomWeaver is a Digital Waveguide Mesh (DWM) based Integrated Development Environment (IDE) style research tool, similar in appearance and functionality to other current acoustics software. The premise of RoomWeaver is to ease the development and application of DWM models for virtual acoustic spaces. This paper demonstrates the basic functionality of RoomWeaver’s 3D modelling and Room Impulse Response (RIR) generation capabilities. A case study is presented to show how new DWM types can be quickly developed and easily tested using RoomWeaver’s built in plug-in architecture through the implementation of a hybrid-type mesh. This hybrid mesh is comprised of efficient, yet geometrically inflexible, finite difference DWM elements and the geometrically versatile, but slow, wave-based DWM elements. The two types of DWM are interfaced using a KW-pipe and this hybrid model exhibits a significant increase in execution speed and a smaller memory footprint than standard wave-based DWM models and allows nontrivial geometries to be successfully modelled.
Download Acoustical Simulations of the Human Vocal Tract Using the 1D and 2D Digital Waveguide Software Model This paper details software under development that uses the digital waveguide physical model to represent the sound creation mechanism and environment associated with the production of speech, specifically the human vocal tract. Focus is directed towards a comparison between the existing 1D waveguide method, on which several studies have already been conducted, and the developing 2D waveguide mesh method. The construction of the two models and the application of the tract geometry is examined, in addition, the inclusion of dynamic articulatory variations to increase the ability of such systems to create natural sounding speech is discussed. Results obtained from each suggest that the 2D model is capable of producing similarly accurate vowel spectra to that already accomplished with the 1D version, although speech-like sounds created with the 2D mesh appear to exhibit greater realism.
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 Investigation of Factors Influencing Acoutsic Characteristics in Geometric Acoustics Based Auralization Most room acoustics simulations and auralization techniques are based on geometric acoustic algorithms, commonly combining image-source and ray-tracing methods for impulse response calculation. This paper investigates the acoustics of a medieval English church and compares a geometric acoustic computer based auralization with measurements obtained from the actual space. More specifically, it focuses on the determination of the influence of different aspects and factors on typical objective room acoustic characteristics. These results are presented and then discussed in terms of how they can be improved and optimized when compared with the measured results.
Download Energy-based calibration of virtual performance systems A Virtual Performance System (VPS) is a real-time 3D auralisation system which allows a musician to play in simulated acoustic environments. Such systems have been used to investigate the effect of stage acoustics on the performance technique of musicians. This article describes the process of calibrating a VPS using energy-based quantities and goes on to verify this technique by comparing known acoustic quantities measured in a test space with a virtual version of the same space. This work has demonstrated that calibrating a VPS using metrics based on Support will result in an accurate simulation of a test space according to known acoustic metrics such as T30. A comparison of quantities referring to earlier parts of the response, such as Early Decay Time (EDT), show some errors which are thought to be caused by the non-anechoic nature of the reproduction space.
Download Audio-Tactile Glove This paper introduces the Audio-Tactile Glove, an experimental tool for the analysis of vibrotactile feedback in instrument design. Vibrotactile feedback provides essential information in the operation of acoustic instruments. The Audio-Tactile Glove is designed as a research tool for the investigation of the various techniques used to apply this theory to digital interfaces. The user receives vibrations via actuators distributed throughout the glove, located so as not to interrupt the physical contact required between user and interface. Using this actuator array, researchers will be able to independently apply vibrotactile information to six stimulation points across each hand exploiting the broad frequency range of the device, with specific sensitivity within the haptic frequency range of the hand. It is proposed that researchers considering the inclusion of vibrotactile feedback in existing devices can utilize this device without altering their initial designs.
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.