Download Bistable Digital Audio Effect A mechanical system is said to be bistable when its moving parts
can rest at two equilibrium positions. The aim of this work is to
model the vibration behaviour of a bistable system and use it to
create a sound effect, taking advantage of the nonlinearities that
characterize such systems. The velocity signal of the bistable system excited by an audio signal is the output of the digital effect.
The latter is coded in C++ language and compiled into VST3 format that can be run as an audio plugin within most of the commercial digital audio workstation software in the market and as a
standalone application. A Web Audio API demonstration is also
available online as a support material.
Download Object-Based Synthesis of Scraping and Rolling Sounds Based on Non-Linear Physical Constraints Sustained contact interactions like scraping and rolling produce a
wide variety of sounds. Previous studies have explored ways to
synthesize these sounds efficiently and intuitively but could not
fully mimic the rich structure of real instances of these sounds.
We present a novel source-filter model for realistic synthesis of
scraping and rolling sounds with physically and perceptually relevant controllable parameters constrained by principles of mechanics. Key features of our model include non-linearities to constrain
the contact force, naturalistic normal force variation for different
motions, and a method for morphing impulse responses within a
material to achieve location-dependence. Perceptual experiments
show that the presented model is able to synthesize realistic scraping and rolling sounds while conveying physical information similar to that in recorded sounds.
Download A Computational Model of the Hammond Organ Vibrato/Chorus using Wave Digital Filters We present a computational model of the Hammond tonewheel organ vibrato/chorus, a musical audio effect comprising an LC ladder circuit and an electromechanical scanner. We model the LC ladder using the Wave Digital Filter (WDF) formalism, and introduce a new approach to resolving multiple nonadaptable linear elements at the root of a WDF tree. Additionally we formalize how to apply the well-known warped Bilinear Transform to WDF discretization of capacitors and inductors and review WDF polarity inverters. To model the scanner we propose a simplified and physically-informed approach. We discuss the time- and frequency-domain behavior of the model, emphasizing the spectral properties of interpolation between the taps of the LC ladder.
Download Shimmer Reverberation with Nonlinear Feedback Delay Networks Shimmer reverberation is an effect used in music production to deliver ethereal, pitch-shifted textures and evolving ambient soundscapes. This paper explores the synthesis of shimmer effects using the feedback delay network architecture, a popular real-time reverberator. We propose five distinct approaches for integrating nonlinear and time-varying operations into the feedback loop, focusing on expanding the harmonic content while adhering to energy-preservation and stability criteria. Our approach can generate a wide range of sonic characteristics, from harmonically rich distortions to musically coherent pitch-shifted reverberation, while maintaining stability and controllable decay behavior.
Download Diagonal Complex-Valued State Space Models for System Identification and Modeling of Metal Plate Reverbs Accurate and interpretable modeling of plate reverbs remains an important challenge in virtual analog modeling of audio effects. While existing neural network-based black-box approaches already achieve high-quality synthesis and strong perceptual quality, they often lack the possibility to identify the underlying physically meaningful complex, long-memory modal behavior. In this work, we address this limitation by proposing a restricted complex-valued diagonal State Space Model (SSM), showing its equivalence to a parallel second-order all-pole filter, also utilizing efficient training via parallel state computation using the parallel scan algorithm. Additionally, we propose a Matrix Pencil (MP) guided eigenvalue initialization, improving synthesis quality and system identification performance.
Download Differentiable Feedback Delay Network for Colorless Reverberation Artificial reverberation algorithms often suffer from spectral coloration, usually in the form of metallic ringing, which impairs the perceived quality of sound. This paper proposes a method to reduce the coloration in the feedback delay network (FDN), a popular artificial reverberation algorithm. An optimization framework is employed entailing a differentiable FDN to learn a set of parameters decreasing coloration. The optimization objective is to minimize the spectral loss to obtain a flat magnitude response, with an additional temporal loss term to control the sparseness of the impulse response. The objective evaluation of the method shows a favorable narrower distribution of modal excitation while retaining the impulse response density. The subjective evaluation demonstrates that the proposed method lowers perceptual coloration of late reverberation, and also shows that the suggested optimization improves sound quality for small FDN sizes. The method proposed in this work constitutes an improvement in the design of accurate and high-quality artificial reverberation, simultaneously offering computational savings.
Download Band-Limited Impulse Invariance Method Using Lagrange Kernels The band-limited impulse invariance method is a recently proposed approach for the discrete-time modeling of an LTI continuoustime system. Both the magnitude and phase responses are accurately modeled by means of discrete-time filters. It is an extension of the conventional impulse invariance method, which is based on the time-domain sampling of the continuous-time response. The resulting IIR filter typically exhibits spectral aliasing artifacts. In the band-limited impulse invariance method, an FIR filter is combined in parallel with the IIR filter, in such a way that the frequency response of the FIR part reduces the aliasing contributions. This method was shown to improve the frequency-domain accuracy while maintaining the compact temporal structure of the discrete-time model. In this paper, a new version of the bandlimited impulse invariance method is introduced, where the FIR coefficients are derived in closed form by examining the discontinuities that occur in the continuous-time domain. An analytical anti-aliasing filtering is performed by replacing the discontinuities with band-limited transients. The band-limited discontinuities are designed by using the anti-derivatives of the Lagrange interpolation kernel. The proposed method is demonstrated by a wave scattering example, where the acoustical impulse responses on a rigid spherical scatter are simulated.
Download Computation of Nonlinear Filter Networks Containing Delay-Free Paths A method for solving filter networks made of linear and nonlinear filters is presented. The method is valid independently of the presence of delay-free paths in the network, provided that the nonlinearities in the system respect certain (weak) hypotheses verified by a wide class of real components: in particular, that the contribution to the output due to the memory of the nonlinear blocks can be extracted from each nonlinearity separately. The method translates into a general procedure for computing the filter network, hence it can serve as a testbed for offline testing of complex audio systems and as a starting point toward further code optimizations aimed at achieving real time.
Download Real-Time Implementation of an Elasto-Plastic Friction Model using Finite-Difference Schemes The simulation of a bowed string is challenging due to the strongly non-linear relationship between the bow and the string. This relationship can be described through a model of friction. Several friction models in the literature have been proposed, from simple velocity dependent to more accurate ones. Similarly, a highly accurate technique to simulate a stiff string is the use of finitedifference time-domain (FDTD) methods. As these models are generally computationally heavy, implementation in real-time is challenging. This paper presents a real-time implementation of the combination of a complex friction model, namely the elastoplastic friction model, and a stiff string simulated using FDTD methods. We show that it is possible to keep the CPU usage of a single bowed string below 6 percent. For real-time control of the bowed string, the Sensel Morph is used.
Download A Modeller-Simulator for Instrumental Playing of Virtual Musical Instruments This paper presents a musician-oriented modelling and simulation environment for designing physically modelled virtual instruments and interacting with them via a high performance haptic device. In particular, our system allows restoring the physical coupling between the user and the manipulated virtual instrument, a key factor for expressive playing of traditional acoustical instruments that is absent in the vast majority of computer-based musical systems. We first analyse the various uses of haptic devices in Computer Music, and introduce the various technologies involved in our system. We then present the modeller and simulation environments, and examples of musical virtual instruments created with this new environment.