Download Spatial audio quality and user preference of listening systems in video games Spatial audio playback solutions provide video game players with ways to experience more immersive and engaging video game content. This paper aims to find whether listening systems that are able to more accurately convey spatial information are preferred by video game players, and to what extent this is true for different loudspeaker configurations whilst engaged in video game play. Results do suggest that a listening system with high perceived spatial quality is more preferred.
Download Real-Time Dynamic Image-Source Implementation For Auralisation This paper describes a software package for auralisation in interactive virtual reality environments. Its purpose is to reproduce, in real time, the 3D soundfield within a virtual room where listener and sound sources can be moved freely. Output sound is presented binaurally using headphones. Auralisation is based on geometric acoustic models combined with head-related transfer functions (HRTFs): the direct sound and reflections from each source are computed dynamically by the image-source method. Directional cues are obtained by filtering these incoming sounds by the HRTFs corresponding to their propagation directions relative to the listener, computed on the basis of the information provided by a head-tracking device. Two interactive real-time applications were developed to demonstrate the operation of this software package. Both provide a visual representation of listener (position and head orientation) and sources (including image sources). One focusses on the auralisation-visualisation synchrony and the other on the dynamic calculation of reflection paths. Computational performance results of the auralisation system are presented.
Download Digitizing the Schumann PLL Analog Harmonizer The Schumann Electronics PLL is a guitar effect that uses hardwarebased processing of one-bit digital signals, with op-amp saturation and CMOS control systems used to generate multiple square waves derived from the frequency of the input signal. The effect may be simulated in the digital domain by cascading stages of statespace virtual analog modeling and algorithmic approximations of CMOS integrated circuits. Phase-locked loops, decade counters, and Schmitt trigger inverters are modeled using logic algorithms, allowing for the comparable digital implementation of the Schumann PLL. Simulation results are presented.
Download A Virtual Tube Delay Effect A virtual tube delay effect based on the real-time simulation of acoustic wave propagation in a garden hose is presented. The paper describes the acoustic measurements conducted and the analysis of the sound propagation in long narrow tubes. The obtained impulse responses are used to design delay lines and digital filters, which simulate the propagation delay, losses, and reflections from the end of the tube which may be open, closed, or acoustically attenuated. A study on the reflection caused by a finite-length tube is described. The resulting system consists of a digital waveguide model and produces delay effects having a realistic low-pass filtering. A stereo delay effect plugin in P URE DATA1 has been implemented and it is described here.
Download Analysis/Synthesis of the Andean Quena via Harmonic Band Wavelet Transform It is well known that one of the challenges in musical instruments analysis is to obtain relevant signal characteristics and information for sound description and classification. In this paper we study the Peruvian quena flute by means of the Harmonic Band Wavelet Transform (HBWT), a convenient representation for the sound content based on its 1/f fractal characteristics. In order to identify a relationship between fractal characteristics of musical sounds, we developed two sound transformations and establish a comparison between quena, a recorder and melodica wind instruments. The sound transformations implemented were noise filtering and pitch-shifting while the sound classification was focused on the γp fractal attribute. Our work led us to the conclusion that the HBWT quena representation favored the implementation of sound transformations and that the γp fractal feature had great potential in musical instruments recognition and classification applications. Keywords: sound fractal analysis; quena; 1/f noise; noise filtering; pitch-shifting.
Download A virtual DSP architecture for MPEG-4 structured audio The MPEG-4 Audio standard provides a toolset for synthetic Audio generation and Audio processing called Structured Audio (SA). SA permits to describe algorithms through its Structured Audio Orchestra Language (SAOL) programming language. Unlike some other languages of the same type, SAOL has a sample-by-sample execution structure, and this makes particularly important the overhead computation in the case of an interpreted decoding. This paper describes the design of a virtual DSP architecture able to exploit the data level parallelism contained in many audio synthesis and processing algorithms and to consistently reduce the implementation overhead.
Download Binauralization of Omnidirectional Room Impulse Responses - Algorithm and Technical Evaluation The auralization of acoustic environments over headphones is often realized with data-based dynamic binaural synthesis. The required binaural room impulse responses (BRIRs) for the convolution process can be acquired by performing measurements with an artificial head for different head orientations and positions. This procedure is rather costly and therefore not always feasible in practice. Because a plausible representation is sufficient for many practical applications, a simpler approach is of interest. In this paper we present the BinRIR (Binauralization of omnidirectional room impulse responses) algorithm, which synthesizes BRIR datasets for dynamic auralization based on a single measured omnidirectional room impulse response (RIR). Direct sound, early reflections, and diffuse reverberation are extracted from the omnidirectional RIR and are separately spatialized. Spatial information is added according to assumptions about the room geometry and on typical properties of diffuse reverberation. The early part of the RIR is described by a parametric model and can easily be modified and adapted. Thus the approach can even be enhanced by considering modifications of the listener position. The late reverberation part is synthesized using binaural noise, which is adapted to the energy decay curve of the measured RIR. In order to examine differences between measured and synthesized BRIRs, we performed a technical evaluation for two rooms. Measured BRIRs are compared to synthesized BRIRs and thus we analyzed the inaccuracies of the proposed algorithm.
Download Perceptual Audio Source Culling for Virtual Environments Existing game engines and virtual reality software, use various techniques to render spatial audio. One such technique, binaural synthesis, is achieved through the use of head-related transfer functions, in conjunction with artificial reverberators. For virtual environments that embody a large number of concurrent sound sources, binaural synthesis will be computationally costly. The work presented in this paper aims to develop a methodology that improves overall performance by culling inaudible and perceptually less prominent sound sources in order to reduce performance implications. The proposed algorithm is benchmarked and compared with distance-based, volumetric culling methodology. A subjective evaluation of the perceptual performance of the proposed algorithm for acoustic scenes having different compositions is also provided.
Download Neural Modelling of Time-Varying Effects This paper proposes a grey-box neural network based approach
to modelling LFO modulated time-varying effects.
The neural
network model receives both the unprocessed audio, as well as
the LFO signal, as input. This allows complete control over the
model’s LFO frequency and shape. The neural networks are trained
using guitar audio, which has to be processed by the target effect
and also annotated with the predicted LFO signal before training.
A measurement signal based on regularly spaced chirps was used
to accurately predict the LFO signal. The model architecture has
been previously shown to be capable of running in real-time on a
modern desktop computer, whilst using relatively little processing
power. We validate our approach creating models of both a phaser
and a flanger effects pedal, and theoretically it can be applied to
any LFO modulated time-varying effect. In the best case, an errorto-signal ratio of 1.3% is achieved when modelling a flanger pedal,
and previous work has shown that this corresponds to the model
being nearly indistinguishable from the target device.
Download A Wave Digital Filter Model of the Fairchild 670 Limiter This paper presents a circuit-based, digital model of the prized 1950’s vintage Fairchild R 670 vacuum tube limiter. The model uses a mixture of black boxes and wave digital filters, as a step toward a fully wave digital filter design. Wave digital filters provide an efficient, modular way to digitally simulate analog circuits. A novel model for the 6386 triode is introduced to simulate the active component in a wave digital filter model of the Fairchild 670’s signal amplifier. The signal amplifier is integrated with a hybrid wave digital filter/black-box sidechain amplifier model to form a complete model of the Fairchild 670. Model test results for music and pure tones are discussed, highlighting the device’s static gain characteristics and gain reduction dependent distortion. Finally, this paper discusses the model’s salient features and their implications for designing dynamics processors.