Download Investigations with the Sonic browser on two of the perceptual auditory dimensions of sound objects: Elasticity and force
The Sonic Browser is a software tool developed especially for navigating among sounds in a 2-D space, primarily through listening. It could be used for managing large collections of sounds, but now it is turning out to be useful also for conducting psychophysical experiments, aiming at investigating perceptual dimension scaling of sounds. We used it for analyzing the relationship between the physical parameters involved in the sound synthesis and for studying the quality of the sounds generated by the SOb models. Some experiments in this direction have been already reported [1, 2], examining real and model generated sounds of impacts and bounces of objects made with different materials. In this paper, we introduce our further investigations, by analyzing perceptually the impacts and bounces sounds from a different perspective, focusing on other two perceptual dimensions, i.e elasticity of the event and the force applied to the dropped object. We will describe the new experiment we conducted and we will report the collected data, by analyzing the resulting perceptual evaluation spaces.
Download On the evaluation of perceptual similarity measures for music
Several applications in the field of content-based interaction with music repositories rely on measures which estimate the perceived similarity of music. These applications include automatic genre recognition, playlist generation, and recommender systems. In this paper we study methods to evaluate the performance of such measures. We compare five measures which use only the information extracted from the audio signal and discuss how these measures can be evaluated qualitatively and quantitatively without resorting to large scale listening tests.
Download Independent subspace analysis using locally linear embedding
While Independent Subspace Analysis provides a means of blindly separating sound sources from a single channel signal, it does have a number of problems. In particular the amount of information required for separation of sources varies with the signal. This is as a result of the variance-based nature of Principal Component Analysis, which is used for dimensional reduction in the Independent Subspace Analysis algorithm. In an attempt to overcome this problem the use of a non-variance based dimensional reduction method, Locally Linear Embedding, is proposed. Locally Linear Embedding is a geometry based dimensional reduction technique. The use of this approach is demonstrated by its application to single channel source separation, and its merits discussed.
Download Interpolation of long gaps in audio signals using the warped Burg's method
This paper addresses the reconstruction of missing samples in audio signals via model-based interpolation schemes. We demonstrate through examples that employing a frequency-warped version of Burg’s method is advantageous for interpolation of long duration signal gaps. Our experiments show that using frequencywarping to focus modeling on low frequencies allows reducing the order of the autoregressive models without degrading the quality of the reconstructed signal. Thus a better balance between qualitative performance and computational complexity can be achieved.
Download Nonlinear time series analysis of musical signals
In this work the techniques of chaotic time series analysis are applied to music. The audio stream from musical recordings are treated as representing experimental data from a dynamical system. Several performance of well-known classical pieces are analysed using recurrence analysis, stationarity measures, information metrics, and other time series based approaches. The benefits of such analysis are reported.
Download Real-time implementation of a source separation algorithm
Source separation out of a mix of signals has been under development for many years with different approaches. We use timefrequency representations of two microphone signals to estimate the mixing parameters of the source signals. In order to evaluate the robustness of the algorithm under real-world conditions we built a real-time implementation, which is suitable to detect the sources, their mixing parameters and performs the source separation based on the mixing parameters. Our implementation only needs a few parameters and then works as a stand-alone solution with the opportunity to apply further post-processing or digital audio effects to the source signals.
Download Algorithm for the separation of harmonic sounds with time-frequency smoothness constraint
A signal model is described which forces temporal and spectral smoothness of harmonic sounds. Smoothness refers to harmonic partials, the amplitudes of which are slowly-varying as a function of time and frequency. An algorithm is proposed for the estimation of the model parameters. The algorithm is utilized in a sound separation system, the robustness of which is increased by the smoothness constraints.
Download Simulation of sound source motion by time-frequency filtering
The generalisation of conventional linear time invariant filter theory from one dimension to the two-dimensional timefrequency (TF) domain provides a powerful tool for the simulation of complex time variable systems. TF filtering is performed as convolution in the TF domain and is based on nonparametric modelling using direct convolution along the time or frequency axis. A method based on short-time Fourier analysis has been developed to produce non-stationary signals with desirable time and frequency characteristics. This method is faster than non-recursive realisations and yields a simple synthesis procedure. The application of filtering in the TF domain for the simulation of sound source motion is presented.
Download Chaotic signal synthesis with real-time control: solving differential equations in PD, MAX/MSP, and JMAX
Chaotic signals are useful in two different levels in audio synthesis: as sound material or control structure. Patching languages such as Pd, Max/MSP, and jMAX provide easier mechanisms for generating chaotic structures at control level. We can generate deterministic chaotic signals either by finding numerical solutions to differential equations or by using first return maps. While generating the next sample, both of these methods require calculations with the knowledge of the previous sample. Most signal processing environments for computer music, such as Pd, Max/MSP, and jMAX, transfer audio data among their objects by vectors (blocks). In such environments, finding numerical solutions to differential equations or generating signals based on first return maps, will require writing external objects or setting the block-size to 1. Writing external objects can be time consuming and the real-time control of the calculations have to be embedded in the external object, which will require a recompilation for every change to the mechanism. Setting the block-size to 1 can make writing the patch cumbersome and sometimes very confusing. In this paper we shall present the fexpr∼ object, implemented for Pd, Max/MSP, and jMAX, which can be used for finding numerical solutions to differential equations by simply entering the difference equations as part of the object arguments. The object parameters can then be controlled in real-time using the host patching language. As examples, solutions to Lorenz Equations, Chua’s Oscillators, Duffing’s equation, and the use of first return maps will be presented using the fexpr∼ object.
Download Using nonlinear amplifier simulation in dynamic range controllers
Amplifying devices where the gain is automatically controlled by the level of the input signal performs dynamics processing. Non-linear components simulating tube amplifiers can be used in these devices to make musical signal audibly dense . This paper deals with the simulation of tube amplifiers using the power polynomial approximation of transfer characteristic and their use in dynamic range controllers. The influence of various non-linear amplifying devices simulating tube amplifiers on the output signal spectrum of dynamic effects is presented as well.