Download Adjusting the Spectral Envelope Evolution of Transposed Sounds with Gabor Mask Prototypes Audio-samplers often require to modify the pitch of recorded sounds in order to generate scales or chords. This article tackles the use of Gabor masks and their capacity to improve the perceptual realism of transposed notes obtained through the classical phasevocoder algorithm. Gabor masks can be seen as operators that allows the modification of time-dependent spectral content of sounds by modifying their time-frequency representation. The goal here is to restore a distribution of energy that is more in line with the physics of the structure that generated the original sound. The Gabor mask is elaborated using an estimation of the spectral envelope evolution in the time-frequency plane, and then applied to the modified Gabor transform. This operation turns the modified Gabor transform into another one which respects the estimated spectral envelope evolution, and therefore leads to a note that is more perceptually convincing.
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 Digital Audio Device Creation by the use of a Domain Specific Language and a Hardware Abstraction Layer The present paper deals with a framework destined to manage different aspects of the creation of digital audio devices. By means of a domain-specific language modelling aspects like signal processing and user interaction are implemented. The problem of different hardware interfaces is resolved by the definition of a hardware abstraction layer. This layer provides different types of variables and functions. A compiler translates the model referring the functions and variables defined at the hardware abstraction layer. Furthermore, the compiler is able to split the model into different parts that can be run on different hardware components. The communication needed to manage the distributed model is defined and formalized by the framework. A simple example is presented to help explain the framework’s parts, as are the compiler and the execution unit.
Download Audio Transport: A Generalized Portamento via Optimal Transport This paper proposes a new method to interpolate between two audio signals. As an interpolation parameter is changed, the pitches in one signal slide to the pitches in the other, producing a portamento, or musical glide. The assignment of pitches in one sound to pitches in the other is accomplished by solving a 1-dimensional optimal transport problem. In addition, we introduce several techniques that preserve the audio fidelity over this highly nonlinear transformation. A portamento is a natural way for a musician to transition between notes, but traditionally it has only been possible for instruments with a continuously variable pitch like the human voice or the violin. Audio transport extends the portamento to any instrument, even polyphonic ones. Moreover, the effect can be used to transition between different instruments, groups of instruments, or any other pair of audio signals. The audio transport effect operates in real-time; we provide an open-source implementation. In experiments with sinusoidal inputs, the interpolating effect is indistinguishable from ideal sine sweeps. More generally, the effect produces clear, musical results for a wide variety of inputs.
Download Audio Content Transmission Content description has become a topic of interest for many researchers in the audiovisual field [1][2]. While manual annotation has been used for many years in different applications, the focus now is on finding automatic contentextraction and content-navigation tools. An increasing number of projects, in some of which we are actively involved, focus on the extraction of meaningful features from an audio signal. Meanwhile, standards like MPEG7 [3] are trying to find a convenient way of describing audiovisual content. Nevertheless, content description is usually thought of as an additional information stream attached to the ‘actual content’ and the only envisioned scenario is that of a search and retrieval framework. However, in this article it will be argued that if there is a suitable content description, the actual content itself may no longer be needed and we can concentrate on transmitting only its description. Thus, the receiver should be able to interpret the information that, in the form of metadata, is available at its inputs, and synthesize new content relying only on this description. It is possibly in the music field where this last step has been further developed, and that fact allows us to think of such a transmission scheme being available on the near future.
Download An Extension for Source Separation Techniques Avoiding Beats The problem of separating individual sound sources from a mixture of these, known as Source Separation or Computational Auditory Scene Analysis (CASA), has become popular in the recent decades. A number of methods have emerged from the study of this problem, some of which perform very well for certain types of audio sources, e.g. speech. For separation of instruments in music, there are several shortcomings. In general when instruments play together they are not independent of each other. More specifically the time-frequency distributions of the different sources will overlap. Harmonic instruments in particular have high probability of overlapping partials. If these overlapping partials are not separated properly, the separated signals will have a different sensation of roughness, and the separation quality degrades. In this paper we present a method to separate overlapping partials in stereo signals. This method looks at the shapes of partial envelopes, and uses minimization of the difference between such shapes in order to demix overlapping partials. The method can be applied to enhance existing methods for source separation, e.g. blind source separation techniques, model based techniques, and spatial separation techniques. We also discuss other simpler methods that can work with mono signals.
Download Physical Modeling of the MXR Phase 90 Guitar Effect Pedal In this study, a famous boxed effect pedal, also called stompbox, for electrical guitars is analyzed and simulated. The nodal DK method is used to create a non-linear state-space system with Matlab as a physical model for the MXR Phase 90 guitar effect pedal. A crucial component of the effect are Junction Field Effect Transistors (JFETs) which are used as variable resistors to dynamically vary the phase-shift characteristic of an allpass-filter cascade. So far, virtual analog modeling in the context of audio has mainly been applied to diode-clippers and vacuum tube circuits. This work shows an efficient way of describing the nonlinear behavior of JFETs, which are wide-spread in audio devices. To demonstrate the applicability of the proposed physical model, a real-time VST audio plug-in was implemented.
Download Antiderivative Antialiasing for Stateful Systems Nonlinear systems, like e.g. guitar distortion effects, play an important role in musical signal processing. One major problem encountered in digital nonlinear systems is aliasing distortion. Consequently, various aliasing reduction methods have been proposed in the literature. One of these is based on using the antiderivative of the nonlinearity and has proven effective, but is limited to memoryless systems. In this work, it is extended to a class of stateful systems which includes but is not limited to systems with a single one-port nonlinearity. Two examples from the realm of virtual analog modeling show its applicability to and effectiveness for commonly encountered guitar distortion effect circuits.
Download Real-Time Physical Modelling For Analog Tape Machines For decades, analog magnetic tape recording was the most popular method for recording music, but has been replaced over the past 30 years first by DAT tape, then by DAWs and audio interfaces. Despite being replaced by higher quality technology, many have sought to recreate a "tape" sound through digital effects, despite the distortion, tape "hiss", and other oddities analog tape produced. The following paper describes the general process of creating a physical model of an analog tape machine starting from basic physical principles, then discusses in-depth a real-time implementation of a physical model of a Sony TC-260 tape machine."Whatever you now find weird, ugly, uncomfortable, and nasty about a new medium will surely become its signature. CD distortion, the jitteriness of digital video, the crap sound of 8-bit - all of these will be cherished and emulated as soon as they can be avoided." -Brian Eno.
Download Continuous State Modeling for Statistical Spectral Synthesis Continuous State Markovian Spectral Modeling is a novel approach for parametric synthesis of spectral modeling parameters, based on the sines plus noise paradigm. The method aims specifically at capturing shimmer and jitter - micro-fluctuations in the partials’ frequency and amplitude trajectories, which are essential for the timbre of musical instruments. It allows for parametric control over the timbral qualities, while removing the need for the more computationally expensive and restrictive process of the discrete state space modeling method. A qualitative comparison between an original violin sound and a re-synthesis shows the ability of the algorithm to reproduce the micro-fluctuations, considering their stochastic and spectral properties.