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 BIVIB: A Multimodal Piano Sample Library Of Binaural Sounds And Keyboard Vibrations An extensive piano sample library consisting of binaural sounds and keyboard vibration signals is made available through an openaccess data repository. Samples were acquired with high-quality audio and vibration measurement equipment on two Yamaha Disklavier pianos (one grand and one upright model) by means of computer-controlled playback of each key at ten different MIDI velocity values. The nominal specifications of the equipment used in the acquisition chain are reported in a companion document, allowing researchers to calculate physical quantities (e.g., acoustic pressure, vibration acceleration) from the recordings. Also, project files are provided for straightforward playback in a free software sampler available for Windows and Mac OS systems. The library is especially suited for acoustic and vibration research on the piano, as well as for research on multimodal interaction with musical instruments.
Download Real-Time Modal Synthesis of Crash Cymbals with Nonlinear Approximations, Using a GPU We apply modal synthesis to create a virtual collection of crash cymbals. Synthesizing each cymbal may require enough modes to stress a modern CPU, so a full drum set would certainly not be tractable in real-time. To work around this, we create a GPU-accelerated modal filterbank, with each individual set piece allocated over two thousand modes. This takes only a fraction of available GPU floating-point throughput. With CPU resources freed up, we explore methods to model the different instrument response in the linear/harmonic and non-linear/inharmonic regions that occur as more energy is present in a cymbal: a simple approach, yet one that preserves the parallelism of the problem, uses multisampling, and a more physically-based approach approximates modal coupling.
Download An Equivalent Circuit Interpretation of Antiderivative Antialiasing The recently proposed antiderivative antialiasing (ADAA) technique for stateful systems involves two key features: 1) replacing a nonlinearity in a physical model or virtual analog simulation
with an antialiased nonlinear system involving antiderivatives of
the nonlinearity and time delays and 2) introducing a digital filter
in cascade with each original delay in the system. Both of these
features introduce the same delay, which is compensated by adjusting the sampling period. The result is a simulation with reduced
aliasing distortion. In this paper, we study ADAA using equivalent
circuits, answering the question: “Which electrical circuit, discretized using the bilinear transform, yields the ADAA system?”
This gives us a new way of looking at the stability of ADAA and
how introducing extra filtering distorts a system’s response. We
focus on the Wave Digital Filter (WDF) version of this technique.
Download Air Absorption Filtering Method Based on Approximate Green's Function for Stokes' Equation Air absorption effects lead to significant attenuation in high frequencies over long distances and this is critical to model in wide-band
virtual acoustic simulations. Air absorption is commonly modelled
using filter banks applied to an impulse response or to individual
impulse events (rays or image sources) arriving at a receiver. Such
filter banks require non-trivial fitting to air absorption attenuation
curves, as a function of time or distance, in the case of IIR approximations, or may suffer from overlap-add artefacts in the case of FIR
approximations. In this study, a filter method is presented which
avoids the aforementioned issues. The proposed approach relies on a
time-varying diffusion kernel that is found in an approximate Green’s
function solution to Stokes’ equation in free space. This kernel acts
as a low-pass filter that is parametrised by physical constants, and can
be applied to an impulse response using time-varying convolution.
Numerical examples are presented demonstrating the utility of this
approach for adding air absorption effects to room impulse responses
simulated using geometrical acoustics or wave-based methods.
Download Neural Modeling of Magnetic Tape Recorders The sound of magnetic recording media, such as open-reel and cassette tape recorders, is still sought after by today’s sound practitioners due to the imperfections embedded in the physics of the magnetic recording process. This paper proposes a method for digitally emulating this character using neural networks. The signal chain of the proposed system consists of three main components: the hysteretic nonlinearity and filtering jointly produced by the magnetic recording process as well as the record and playback amplifiers, the fluctuating delay originating from the tape transport, and the combined additive noise component from various electromagnetic origins. In our approach, the hysteretic nonlinear block is modeled using a recurrent neural network, while the delay trajectories and the noise component are generated using separate diffusion models, which employ U-net deep convolutional neural networks. According to the conducted objective evaluation, the proposed architecture faithfully captures the character of the magnetic tape recorder. The results of this study can be used to construct virtual replicas of vintage sound recording devices with applications in music production and audio antiquing tasks.
Download Frequency-Dependent Boundary Condition for the 3-D Digital Waveguide Mesh The three-dimensional digital waveguide mesh is a method for modeling the propagation of sound waves in space. It provides a simulation of the state of the whole soundfield at discrete timesteps. The updating functions of the mesh can be formulated either using physical values of sound pressure or particle velocity, also called the Kirchhoff values, or using a wave decomposition of these instead. Computation in homogenous media is significantly lighter using Kirchhoff variables, but frequency-dependent boundary conditions are more easily defined with wave variables. In this paper a conversion method between these two variable types has been further simplified. Using the resulting structure, a novel method for defining the mesh boundaries with digital filters is introduced. With this new method, the reflection coefficients can be defined in a frequency-dependent manner at the boundaries of a Kirchhoff variable mesh. This leads to computationally lighter and more realistic simulations than previous solutions.
Download Accurate Reverberation Time Control in Feedback Delay Networks The reverberation time is one of the most prominent acoustical qualities of a physical room. Therefore, it is crucial that artificial reverberation algorithms match a specified target reverberation time accurately. In feedback delay networks, a popular framework for modeling room acoustics, the reverberation time is determined by combining delay and attenuation filters such that the frequencydependent attenuation response is proportional to the delay length and by this complying to a global attenuation-per-second. However, only few details are available on the attenuation filter design as the approximation errors of the filter design are often regarded negligible. In this work, we demonstrate that the error of the filter approximation propagates in a non-linear fashion to the resulting reverberation time possibly causing large deviation from the specified target. For the special case of a proportional graphic equalizer, we propose a non-linear least squares solution and demonstrate the improved accuracy with a Monte Carlo simulation.
Download Real-Time Modal Synthesis of Nonlinearly Interconnected Networks Modal methods are a long-established approach to physical modeling sound synthesis. Projecting the equation of motion of a linear, time-invariant system onto a basis of eigenfunctions yields a set of independent forced, lossy oscillators, which may be simulated efficiently and accurately by means of standard time-stepping methods. Extensions of modal techniques to nonlinear problems are possible, though often requiring the solution of densely coupled nonlinear time-dependent equations. Here, an application of recent results in numerical simulation design is employed, in which the nonlinear energy is first quadratised via a convenient auxiliary variable. The resulting equations may be updated in time explicitly, thus avoiding the need for expensive iterative solvers, dense linear system solutions, or matrix inversions. The case of a network of interconnected distributed elements is detailed, along with a real-time implementation as an audio plugin.
Download Quadratic Spline Approximation of the Contact Potential for Real-Time Simulation of Lumped Collisions in Musical Instruments Collisions are an integral part of the sound production mechanism in a wide variety of musical instruments. In physics-based realtime simulation of such nonlinear phenomena, challenges centred around efficient and accurate root-finding arise. Nonlinearly implicit schemes are normally ill-suited for real-time simulation as they rely on iterative solvers for root-solving. Explicit schemes overcome this issue at the cost of a slightly larger error for a given sample rate. In this paper, for the case of lumped collisions, an alternate approach is proposed by approximating the contact potential curve. The approximation is described, and is shown to lead to a non-iterative update for an energy-stable nonlinearly implicit scheme. The method is first tested on single mass-barrier collision simulations, and then employed in conjunction with a modal string model to simulate hammer-string and slide-string interaction. Results are discussed in comparison with existing approaches, and real-time feasibility is demonstrated.