Download Real-Time Simulation of a Guitar Power Amplifier This paper deals with the real time simulation of a class A single ended guitar power amplifier. Power tubes and triode models are compared, based on Norman Koren’s work. Beam tetrodes and pentodes characteristics are discussed, and displayed as Norman Koren’s model parameters. A simple output transformer model is considered, with its parameters calculated from datasheets specifications. Then, the circuit is modeled by a nonlinear differential algebraic system, with extended state-space representations. Standard numerical schemes yield efficient and stable simulations of the stage, and are implemented as VST plug-ins.
Download Harmonize-Decompose Audio Signals with Global Amplitude and Frequency Modulations A key building block in music transcription and indexing operations is the decomposition of music signals into notes. We model a note signal as a periodic signal with slow (frequency-selective) amplitude modulation and global frequency-warping. Global frequency-warping allows for an inharmonic frequency modulation, while the global amplitude modulation allows the various harmonics of the periodic signal to decay at different speeds. The global frequency-warping is achieved by a Laguerre transform (that has shown to fit stiffed strings inharmonic behavior). Assuming additive noise, the estimation of the model parameters and the optimization is performed in a Harmonize-Extract fashion. Simulations illustrate that the extraction technique oversteps the limitation of the global AM-FM representation and analysis techniques and allows the processing of inharmonic string instruments (e.g. piano).
Download Do You Hear a Bump or a Hole? An Experiment on Temporal Aspects in Footsteps Recognition In this paper, we present a preliminary experiment whose goal is to assess the role of temporal aspects in sonically simulating the act of walking on a bump or a hole. In particular, we investigate whether the timing between heel and toe and the timing between footsteps affects the perception of walking on unflat surfaces. Results show that it is possible to simulate a bump or a hole by only using temporal information in the auditory modality.
Download Practical Modeling of Bucket-Brigade Device Circuits This paper discusses the sonic characteristics of the bucket-brigade device (BBD) and associated circuitry. BBDs are integrated circuits which produce a time-delayed version of an input signal. In order to reduce aliasing, distortion, and noise, BBDs are typically accompanied by low-pass filters and compander circuitry. Through circuit analysis and measurements, each component of the BBD system can be accurately modeled.
Download MultiBin: A Binaural Audition Tool MultiBin is a new tool for binaural audition of multiple sound sources in a user definable environment. Although designed to be flexible in its application, its primary function is to provide dynamic multi-channel binaural simulation. It is built upon two new Csound binaural reverberation opcodes. An early reflection opcode, based on an image source method and a Head-Related Transfer Function interpolation algorithm previously introduced by the authors provides dynamic source and listener location. This is complemented by a later reverberation opcode which provides a diffuse reverb based on a parametric Feedback Delay Network model which considers interaural coherence.
Download Bibliometric Study of the DAFx Proceedings 1998 - 2009 In this paper we present a bibliometric study of the Digital Audio Effects (DAFx) conference proceedings from 1998 to 2009. Using the online DAFx proceedings, we constructed a DAFx database (LaTeX) to study its bibliometric statistics in terms of research topics, growth of literature, authorship distribution, citation patterns, and frequency distribution of scientific productivity. Results showed that the DAFx literature (with quasi-linear accumulative growth) now consists of 722 contributions (including key notes, papers and posters) from 767 unique authors, from which we identified the 20 top DAFx contributors. Using Google Scholar, we identified that the top 10 most cited DAFx papers (between 43 to 65 times) are in majority (8/10) dealing with sound and music analysis (e.g. extraction of sinusoids, musical genre classification, perceived intensity of music, and musical note onset detection). This study also confirmed that the DAFx literature conforms to the Lokta’s law (n=2.0771 and C=0.6336) at 0.01 level of significance using the Kolmogorov-Smirnov test (KS-test) of goodnessof-fit. The DAFx database will serve as the basis for an Author Cocitation Analysis (ACA) and to create a DAFx conferences archive DVD.
Download Digital Emulation of Distortion Effects by Wave and Phase Shaping Methods This paper will consider wave (amplitude) and phase signal shaping techniques for the digital emulation of distortion effect processing. We examine how to determine the Wave- and Phaseshaping functions with harmonic amplitude and phase data. Three distortion effects units are used to provide test data. The action of the Wave- and Phase- shaping functions derived for these effects is demonstrated with the assistance of a superresolution frequency-domain analysis technique.
Download GPU-Based Spectral Model Synthesis for Real-Time Sound Rendering The timbre of an instrument is usually represented by sinusoids plus noise. Spectral modeling synthesis (SMS) is an audio synthesis technique which can create musical timbre and give control over the frequency and amplitude. Additive synthesis and LPC synthesis are usually applied for synthesizing sinusoids and residuals, respectively. However, it takes fairly large computing power while implementing the algorithms. The purpose of this paper is to present GPU-based techniques of implementing SMS for real-time audio processing by using parallelism and programmability in graphics pipeline. The performance is compared to CPU-based implementations.
Download High-Performance Real-Time FIR-Filtering Using Fast Convolution on Graphics Hardware In this paper we examine how graphic hardware can be used for real-time FIR filtering. We implement uniformly-partitioned fast convolution in the frequency-domain and evaluate its performance on a NVIDIA GTX 285 graphics card. Motivated by audio rendering for virtual reality, our focus lies on large-scale realtime filtering with a multitude of channels, long impulse responses and low latencies. Graphics hardware has already been used for audio signal processing — including FIR and IIR filtering with respect to offline and real-time processing. However, the combination of GPU computing and real-time conditions leads to a number of challenges that have not been reviewed in detail. The new contribution of this paper is an implementation and detailled analysis of a frequency-domain fast convolution method on GPUs. We discuss specific problems that emerge under real-time conditions. Our method allows to achieve an outstanding real-time filtering performance. In this work, we do not only regard a timeinvariant filtering, but also time-varying filtering, where filters are exchanged during runtime. Furthermore, we examine the opportunities of distributed computation — using CPU and GPU — in order to maximize the performance. Finally, we identify bottlenecks and explain their impact on filter exchange latencies and update rates.
Download A Method of Generic Programming for High Performance DSP This paper presents some key concepts for a new just in time programming language designed for high performance DSP. The language is primarily intended to implement an updated version of PWGLSynth, the synthesis extension to the visual musical programming environment PWGL. However, the system is suitable for use as a backend for any DSP platform. A flow control mechanism based on generic programming, polymorphism and functional programming practices is presented, which we believe is much better suited for visual programming than traditional loop constructs found in textual languages.