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 Semi-automatic Ambience Generation Ambiances are background recordings used in audiovisual productions to make listeners feel they are in places like a pub or a farm. Accessing to commercially available atmosphere libraries is a convenient alternative to sending teams to record ambiances yet they limit the creation in different ways. First, they are already mixed, which reduces the flexibility to add, remove individual sounds or change its panning. Secondly, the number of ambient libraries is limited. We propose a semi-automatic system for ambiance generation. The system creates ambiances on demand given text queries by fetching relevant sounds from a large sound effect database and importing them into a sequencer multitrack project. Ambiances of diverse nature can be created easily. Several controls are provided to the users to refine the type of samples and the sound arrangement.
Download Pyroadacoustics: A Road Acoustics Simulator Based on Variable Length Delay Lines In the development of algorithms for sound source detection, identification and localization, having the possibility to generate datasets in a flexible and fast way is of utmost importance. However, most of the available acoustic simulators used for this purpose target indoor applications, and their usefulness is limited when it comes to outdoor environments such as that of a road, involving fast moving sources and long distances travelled by the sound waves. In this paper we present an acoustic propagation simulator specifically designed for road scenarios. In particular, the proposed Python software package enables to simulate the observed sound resulting from a source moving on an arbitrary trajectory relative to the observer, exploiting variable length delay lines to implement sound propagation and Doppler effect. An acoustic model of the road reflection and air absorption properties has been designed and implemented using digital FIR filters. The architecture of the proposed software is flexible and open to extensions, allowing the package to kick-start the implementation of further outdoor acoustic simulation scenarios.
Download On the control of the phase of resonant filters with applications to percussive sound modeling Source-filter models are widely used in numerous audio processing fields, from speech processing to percussive/contact sound synthesis. The design of filters for these models—be it from scratch or from spectral analysis—usually involves tuning frequency and damping parameters and/or providing an all-pole model of the resonant part of the filter. In this context, and for the modelling of percussive (non-sustained) sounds, a source signal can be estimated from a filtered sound through a time-domain deconvolution process. The result can be plagued with artifacts when resonances exhibit very low bandwidth and lie very close in frequency. We propose in this paper a method that noticeably reduces the artifacts of the deconvolution process through an inter-resonance phase synchronization. Results show that the proposed method is able to design filters inducing fewer artifacts at the expense of a higher dynamic range.
Download A generalized 3-d resonator model for simulation of non rectangular shapes A rectangular enclosure has such an even distribution of resonances that it can be accurately modeled using a feedback delay network, but a non rectangular shape such as a sphere has resonances that are distributed according to the extremal points of the spherical Bessel functions. This work proposes an extension of the already known feedback delay network structure to model a non rectangular shape such as a sphere. A speci c frequency distribution of resonances can be approximated, up to a certain frequency, by inserting an allpass lter of moderate order after the delay line within the comb lter structure. The feedback delay network used for rectangular boxes is therefore augmented with a set of allpass lters allowing parametric control over the enclosure size and the boundary properties. This work was motivated by informal listening tests which have shown that it is possible to identify a basic shape just from the distribution of its audible resonances.
Download The Mellin Pizzicator In this paper an application of the Mellin transform to the digital audio effects will be presented. Namely, low-pass and band-pass like filtering in the Mellin domain will be described and used for obtaining some kind of pizzicato effect on audio samples (musical instruments, but not only). The pluck and damp effects will be obtained using filtering in Mellin domain only. The algorithm used for implementing the Mellin (scale) transform has been presented in DAFx’04 [1].
Download Classification Of Music Signals In The Visual Domain With the huge increase in the availability of digital music, it has become more important to automate the task of querying a database of musical pieces. At the same time, a computational solution of this task might give us an insight into how humans perceive and classify music. In this paper, we discuss our attempts to classify music into three broad categories: rock, classical and jazz. We discuss the feature extraction process and the particular choice of features that we used- spectrograms and mel scaled cepstral coefficients (MFCC). We use the texture-of- texture models to generate feature vectors out of these. Together, these features are capable of capturing the frequency-power profile of the sound as the song proceeds. Finally, we attempt to classify the generated data using a variety of classifiers. we discuss our results and the inferences that can be drawn from them.
Download Sinusoidal Synthesis Method using a Force-based Algorithmm In this paper we propose a synthesis method using a force-based algorithm to control frequencies of multiple sine waves. In order to implement this synthesis method, we analyze an existing sound source using a fast Fourier transform (FFT). Spectral peaks which have large magnitudes are regarded as heavy partials and assigned large attractive forces. A few hundred sine waves with stationary amplitudes are placed in a frequency space on which forces generated in the analysis phase are applied. The frequencies of the partials gravitate to the nearest peak of the reference spectrum from the source sound. As more sine waves are combined at the large peaks, the sound synthesized by the partials gradually transforms into the reference spectrum. In order to prevent the frequencies of the partials from gravitating onto localized peaks, each partial is assigned a repulsive force against all others. Through successful control of these attractive and repulsive forces, roughness and speed variation of the synthesis can be achieved. Moreover, by increasing or decreasing the number of partials according to the total amplitude of the source sound, amplitude envelope following is achieved.
Download A New Functional Framework for a Sound System for Realtime Flight Simulation We will show a new sound framework and concept for realistic flight simulation. Dealing with a highly complex network of mechanical systems that act as physical sound sources the main focus is on a fully modular and extensible/scalable design. The prototype we developed is part of a fully functional Full Flight Simulator for Pilot Training.