Download Binaural partial tracking
Partial tracking in sinusoidal models have been studied for over twenty years now, and have been enhanced, making it precise and useful to analyse noiseless harmonic sounds. However, such tools have always been used in a monophonic (single channel) context. A method is thus proposed to adapt the partial tracking to the case of binaural signals. This gives a tool to perform spectral analysis of such signals, keeping relevant information from both left and right channels. Moreover, azimuth (position in the horizontal plane) information for each partial is gained using interaural cues, such as interaural time differences (ITDs) and interaural level differences (ILDs). The azimuth information can then be used as an attribute or as a constraint in the binaural partial tracking algorithm. Finally, some classification results using the azimuth of partials are presented.
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 A supervised learning approach to ambience extraction from mono recordings for blind upmixing
A supervised learning approach to ambience extraction from onechannel audio signals is presented. The extracted ambient signals are applied for the blind upmixing of musical audio recordings to surround sound formats. The input signal is processed by means of short-term spectral attenuation. The spectral weights are computed using a low-level feature extraction process and a neural network regression method. The multi-channel audio signal is generated by feeding the computed ambient signal into the rear channels of a surround sound system.
Download Direct simulation for wind instrument synthesis
There are now a number of methods available for generating synthetic sound based on physical models of wind instruments, including digital waveguides, wave digital filters, impedance-based methods and those involving impulse responses. Normally such methods are used to simulate the behaviour of the resonator, and the coupling to the excitation mechanism is carried out by making use of simple lumped finite difference schemes or digital filter structures. In almost all cases, a traveling wave, frequencydomain, or impulse response description of the resonator is used as a starting point—efficient structures may be arrived at when the bore is of a particularly simple form, such as a cylinder or cone. In recent years, however, due to the great computing power available, efficiency has become less of a concern—this is especially the case for musical instruments which may be well-modelled in 1D, such as wind instruments. In this paper, a fully time-space discrete algorithm for the simulation and synthesis of woodwind instrument sounds is presented; such a method, though somewhat more computationally intensive than an efficient waveguide structure, is still well within the realm of real-time performance. The main benefits of such a method are its generality (it is no longer necessary to make any assumptions about bore profile, which may be handled in an almost trivial manner), extensibility (i.e., the model may be generalized to handle nonlinear phenomena directly), ease of programming, and the possibility of direct proofs of numerical stability without invoking frequency domain concepts. Simulation results, sound examples and a graphical user interface, in the Matlab programming language are also presented.
Download Energy-stable modelling of contacting modal objects with piece-wise linear interaction force
In discrete-time digital models of contact of vibrating objects stability and therefore control over system energy is an important issue. While numerical approximation is problematic in this context digital algorithms may meat this challenge when based on exact mathematical solution of the underlying equation. The latter may generally be possible under certain conditions of linearity. While a system of contacting solid objects is non-linear by definition, piece-wise linear models may be used. Here however the aspect of “switching” between different linear phases is crucial. An approach is presented for exact preservation of system energy when passing between different phases of contact. One basic principle used may be pictured as inserting appropriate ideal, massless and perfectly stiff, “connection rods” at discrete moments of phase switching. Theoretic foundations are introduced and the general technique is explained and tested at two simple examples.
Download Improvement of band extension technique for G.711 telephony speech based on full wave rectification
This study investigates a band extension technique for the narrow-band speech encoded with G.711, the most common codec for digital speech communications such as VoIP. The proposed technique is based on the full wave rectification that generates high-band harmonics by nonlinear processing. In order to improve the conventional technique, this study focuses on the parameter control according to the characteristics of speech data. From the subjective evaluation, it is indicated that the proposed technique may potentially outperform the conventional technique.
Download Digital simulation of the diode ring modulator for musical applications
In this article, a model of the diode ring modulator is developed, which is based on a model from the literature, but modified to suit musical applications. After a brief introduction to analog ring modulation, a substitute circuit for the diode ring modulator is presented and analyzed, leading to a system of ordinary differential equations (ODEs) of first order. The equations are solved by using Euler’s method. The model is compared with a real ring modulator using the same input waveforms, showing a good match between the simulation and the real device.
Download Real-time dissonancizers: Two dissonance-augmenting audio effects
We present two simple perceptually motivated audio effects designed to increase the perceived sensory dissonance/roughness (a process we call “dissonancization”) of audio input. The first involves heterodyning multiple bands of the audio signal at different frequencies to break each sinusoid in each band into two sinusoids separated in frequency by the amount that Kameoka and Kuriyagawa [1] predict will produce a maximally dissonant effect. The second attempts to increase the depth of modulation caused by existing beating partials by exponentiating the amplitude envelope within small bands, enhancing the perceived roughness already present in the signal. The first algorithm can produce very dramatic effects even for very consonant inputs, whereas the second tends to produce a more subtle effect. Both algorithms are quite simple to understand and implement and computationally inexpensive enough to be used in real time, but produce perceptually interesting results. The effects can be selectively applied so as to affect only desired frequency ranges, and can be continuously controlled (e.g. in a performance context) to have more or less impact.
Download Physical parameters of an oscillator changed by active control: application to a xylophone bar
By applying active control to an oscillator, its modal behaviour changes. This paper makes a comparison between a second order damped harmonic oscillator and a xylophone bar’s mode. Then it proposes a method for acting on an eigen resonance of a xylophone bar. The purpose is to get sound modifications, by bringing under quantitative and independent control its pitch and its duration. Thus it extends our previous work [1], by using a digital feedback controller.
Download Automated rhythmic transformation of musical audio
Time-scale transformations of audio signals have traditionally relied exclusively upon manipulations of tempo. We present a novel technique for automatic mixing and synchronization between two musical signals. In this transformation, the original signal assumes the tempo, meter, and rhythmic structure of the model signal, while the extracted downbeats and salient intra-measure infrastructure of the original are maintained.