Digital audio effects and physical modeling

International audienceThis article describes a research oriented in creating physical models that would transform and process sounds using the CORDIS-ANIMA formalism. Basically the idea was to explore for the first time systematically the capabilities of this physical modeling language and more precisely the GENESIS environment for the creation of Digital Audio Effects. This presentation introduces some elementary signal processing operations and properties using the compositional blocks of CORDIS-ANIMA. Also two physical models will be described that they behave like some classical filters and time varying filters. The idea and the challenge is to give a physical meaning to these widely used algorithms

A Step Toward AI Tools for Quality Control and Musicological Analysis of Digitized Analogue Recordings: Recognition of Audio Tape Equalizations

Historical analogue audio documents are indissolubly linked to their physical carriers on which they are recorded. Because of their short life expectancy these documents have to be digitized. During this process, the document may be altered with the result that the digital copy is not reliable from the authenticity point of view. This happens because digitization process is not completely automatized and sometimes it is influenced by human subjective choices. Artificial intelligence can help operators to avoid errors, enhancing reliability and accuracy, and becoming the base for quality control tools. Furthermore, this kind of algorithms could be part of new instruments aiming to ease and to enrich musicological studies. This work focuses the attention on the equalization recognition problem in the audio tape recording field. The results presented in this paper, highlight that, using machine learning algorithms, is possible to recognize the pre-emphasis equalization used to record an audio tape

Efficient Synthesis of Room Acoustics via Scattering Delay Networks

An acoustic reverberator consisting of a network of delay lines connected via scattering junctions is proposed. All parameters of the reverberator are derived from physical properties of the enclosure it simulates. It allows for simulation of unequal and frequency-dependent wall absorption, as well as directional sources and microphones. The reverberator renders the first-order reflections exactly, while making progressively coarser approximations of higher-order reflections. The rate of energy decay is close to that obtained with the image method (IM) and consistent with the predictions of Sabine and Eyring equations. The time evolution of the normalized echo density, which was previously shown to be correlated with the perceived texture of reverberation, is also close to that of IM. However, its computational complexity is one to two orders of magnitude lower, comparable to the computational complexity of a feedback delay network (FDN), and its memory requirements are negligible

Fractionally-addressed delay lines

While traditional implementations of variable-length digital delay lines are based on a circular buffer accessed by two pointers, we propose an implementation where a single fractional pointer is used both for read and write operations. On modern general-purpose architectures, the proposed method is nearly as efficient as the popularinterpolated circular buffer, and it behaves well for delay-length modulations commonly found in digital audio effects. The physical interpretation of the new implementation shows that it is suitable for simulating tension or density modulations in wave-propagating media.Comment: 11 pages, 19 figures, to be published in IEEE Transactions on Speech and Audio Processing Corrected ACM-clas

Real-time dynamic articulations in the 2-D waveguide mesh vocal tract model

Time domain articulatory vocal tract modeling in one-dimensional (1-D) is well established. Previous studies into two-dimensional (2-D) simulation of wave propagation in the vocal tract have shown it to present accurate static vowel synthesis. However, little has been done to demonstrate how such a model might accommodate the dynamic tract shape changes necessary in modeling speech. Two methods of applying the area function to the 2-D digital waveguide mesh vocal tract model are presented here. First, a method based on mapping the cross-sectional area onto the number of waveguides across the mesh, termed a widthwise mapping approach is detailed. Discontinuity problems associated with the dynamic manipulation of the model are highlighted. Second, a new method is examined that uses a static-shaped rectangular mesh with the area function translated into an impedance map which is then applied to each waveguide. Two approaches for constructing such a map are demonstrated; one using a linear impedance increase to model a constriction to the tract and another using a raised cosine function. Recommendations are made towards the use of the cosine method as it allows for a wider central propagational channel. It is also shown that this impedance mapping approach allows for stable dynamic shape changes and also permits a reduction in sampling frequency leading to real-time interaction with the model

Modelling Methods for the Highly Dispersive Slinky Spring: A Novel Musical Toy

ABSTRACT The 'Slinky' spring is a popular and beloved toy for many children. Like its smaller relatives, used in spring reverberation units, it can produce interesting sonic behaviors. We explore the behavior of the 'Slinky' spring via measurement, and discover that its sonic characteristics are notably different to those of smaller springs. We discuss methods of modeling the behavior of a Slinky via the use of finite-difference techniques and digital waveguides. We then apply these models in different structures to build a number of interesting tools for computer-based music production