Download Using Ideas from Natural Selection to Evolve Synthesized Sounds This paper describes a system for the automatic creation of digital synthesizer circuits that can generate sounds similar to a sampled (target) sound. The circuits will consist of very basic signal functions and generators that are arbitrarily interconnected. The system uses a “genetic algorithm” (GA) to evolve successively better circuits. First it creates populations of such synthesizers, generates the output and a fitness value of each individual circuit. The ones that are best at imitating the target sound will be kept. They are used for “breeding” to form a new generation where, hopefully, at least some individuals perform better than their parents did. The end result will be a circuit that can create a sound that resembles the target sample. Because it’s a synthesizer we can manipulate the different parameters when generating the sound. We can also get a very compact representation of the sound that can be useful when distributing music over a limited bandwidth communications channel (e.g. Internet). As we shall see, it also gives the user a very powerful tool for creating totally new sounds.
Download Sound Modeling from the Analysis of Real Sounds This work addresses sound modeling using a combination of physical and signal models with a particular emphasis on the flute sound. For that purpose, analysis methods adapted to the nonstationary nature of sounds are developed. Further on parameters characterizing the sound from a perceptive and a physical point of view are extracted. The synthesis process is then designed to reproduce a perceptive effect and to simulate the physical behavior of the sound generating system. The correspondence between analysis and synthesis parameters is crucial and can be achieved using both mathematical and perceptive criteria. Real-time control of such models makes it possible to use specially designed interfaces mirroring already existing sound generators like traditional musical instruments.
Download Audio Processing Systems This tutorial1 gives an introduction into several hardware aspects for designing audio processing systems based on digital signal processors (DSP). Digital signal processors of different manufacturers and their use in practical circuits will be discussed.
Download Extracting Sinusoids From Harmonic Audio Signals This paper presents a special window function for a Fast Fourier Transform (FFT) based spectral modeling approach for signals consisting of sinusoids plus noise. The main new idea is to choose a time window function with a simple Fourier transform. With the knowledge of the Fourier transform of the window function we are able to extract the parameters (frequency, amplitude, and phase) of sinusoids in real-time with a digital signal processor.
Download Resynthesis of coupled piano strings vibrations based on physical modeling This paper presents a technique to resynthesize the sound generated by the vibrations of two piano strings tuned to a very close pitch and coupled at the bridge level. Such a mechanical system produces doublets of components generating beats and double decays on the amplitudes of the partials of the sound. We design a waveguide model by coupling two elementary waveguide models. This model is able to reproduce perceptually relevant sounds. The parameters of the model are estimated from the analysis of real signals collected directly on the strings by laser velocimetry. Sound transformations can be achieved by modifying relevant parameters and simulate physical situations.
Download Visual representations of digital audio effects and of their control This article gathers some reflections on how the graphical representations of sound and the graphical interfaces can help making and controlling digital audio effects. Time-frequency visual representations can help understand digital audio effects but are also a tool in themselves for these sound transformations. The basic laws for analysistransformations-resynthesis will be recalled. Graphical interfaces help for the control of effects. The choice of a relation between user control parameters and the effective values for the effect show the importance of the mapping and the graphical design. Graphical and sonic editor programs have both in common the use of plug-ins, which use the same kind of interface and deal with the same kind of approach.
Download The Cpld As A General Physical Modeling Synthesis Engine In this paper we propose a system based on a Complex Programmable Logic Device (CPLD) as a physical modeling synthesis engine and a hardware description language (VHDL) to implement the physical modeling synthesis algorithms. An evaluation of VHDL and CPLD technologies for this application was performed. As an example we have programmed the Karplus-Strong plucked string algorithm using VHDL on an Altera CPLD.
Download Matlab Implementation of Reverberation Algorithms In this paper, we present the implementation of different reverberation algorithms in the Matlab programming environment. This is a useful tool to analyze the algorithms behavior from the signal processing and sounding point of view. With Matlab environment is possible and simple to view the filter characteristics, impulse response, phase response and all the relevant characteristics of the filters. In addition, the possibility of hearing the results is quite simple and fast. We present the main aspects of programming these algorithms using Matlab and the results produced with these techniques
Download Decomposition of steady state instrument data into excitation system and formant filter components This paper describes a method for decomposing steady-state instrument data into excitation and formant filter components. The input data, taken from several series of recordings of acoustical instruments is analyzed in the frequency domain, and for each series a model is built, which most accurately represents the data as a source-filter system. The source part is taken to be a harmonic excitation system with frequency-invariant magnitudes, and the filter part is considered to be responsible for all spectral inhomogenieties. This method has been applied to the SHARC database of steady state instrument data to create source-filter models for a large number of acoustical instruments. Subsequent use of such models can have a wide variety of applications, including wavetable and physical modeling synthesis, high quality pitch shifting, and creation of “hybrid” instrument timbres.
Download Additive Analysis/Synthesis Using Analytically Derived Windows This paper presents a simple and easy way to obtain good estimates of the frequencies of spectral peaks in voiced sounds. The instantaneous frequency throughout the spectrum is calculated using an analytically derived window. Peaks are detected by examining the difference between the frequencies of spectral lines and their corresponding instantaneous frequencies. The instantaneous frequencies near peaks are used as estimates of their actual frequencies. The corresponding amplitude values are calculated from the Gabor transform at the estimated frequencies. The performance of the estimation of the frequencies using analytically derived windows has been verified using synthetic signals and musical sounds. This method gives a better estimate of the instantaneous frequency than commonly used methods and the resynthesis of sound from the additive parameters gives good results.