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 Fractal Modulation Effects Fractal modulation is obtained by forming a power weighted superposition of scaled and modulated versions of the signal. The resulting signal is self-similar with fractal characteristics. In this paper we explore fractal modulation as a powerful method to generate rich signals, useful both for the synthesis of complex sounds, like the sounds from natural events or ecological sounds, or as control functions of audio effects. The wavelet transform can be used as an efficient tool in order to generate a subset of fractal modulated signals that are power homogeneous. Any signal used as a seed for fractal modulation is transformed into a multiscale sound by means of a tree-structured multirate filter bank. Moreover, by superimposing a structured modulation scheme one can generate pseudo-periodic sounds whose partials have fractal behavior.
Download An Interdisciplinary Approach to Audio Effect Classification The aim of this paper is to propose an interdisciplinary classification of digital audio effects to facilitate communication and collaborations between DSP programmers, sound engineers, composers, performers and musicologists. After reviewing classifications reflecting technological, technical and perceptual points of view, we introduce a transverse classification to link disciplinespecific classifications into a single network containing various layers of descriptors, ranging from low-level features to high-level features. Simple tools using the interdisciplinary classification are introduced to facilitate the navigation between effects, underlying techniques, perceptual attributes and semantic descriptors. Finally, concluding remarks on implications for teaching purposes and for the development of audio effects user interfaces based on perceptual features rather than technical parameters are presented.
Download On the Dynamics of the Harpsichord and its Synthesis It is common knowledge that the piano was developed to produce a keyboard instrument with a larger dynamic range and higher sound radiation level than the harpsichord possesses. Also, the harpsichord is a plucked string instrument with a very controlled mechanism to excite the string. For these reasons it is often falsely understood that the harpsichord does not exhibit any dynamic variation. On the contrary, the signal analysis and the listening test made in the this study show that minor but audible differences in the dynamic levels exist. The signal analysis portrays that stronger playing forces produce higher levels in harmonics. The energy given by the player is not only distributed to the plucking mechanism but also carried on from the key to the body. This is evident from the increased level of body mode radiation. A synthesis model for approximating the dynamic behavior of the harpsichord is also proposed. It contains gain and timbre control, and a parallel filter structure to simulate the soundboard knock characteristic for high key velocity tones.
Download Musical Sound Timbre: Verbal Description and Dimensions Two approaches to the study of musical sound timbre are described and documented by psychoacoustic experiment examples. The classical bottom-up approach is demonstrated on the study of contexts of violin sounds and pipe organ sounds. Verbal attributes collected during listening tests were used for the interpretation and comparison of resulted perceptual spaces of sounds. The proposed top-down approach is based on the collection of musical experts experiences and opinions going from very common to more specific ones. Here the common perceptual space (perceptual space of verbal attributes) was constructed from nonlistening test of dissimilarity of verbal attributes describing timbre (verbal or soundfree context of stimuli). The verbal interpretation of perceptual spaces of sound contexts and perceptual space of verbal attributes are compared and the hypothesis of the four basic dimensions of timbre is formulated: 1. gloomy — clear, 2. harsh — delicate, 3. full — narrow, 4. noisy — ?.
Download Musical Key Estimation of Audio Signal Based on Hidden Markov Modeling of Chroma Vectors In this paper, we propose a system for the automatic estimation of the key of a music track using hidden Markov models. The front-end of the system performs transient/noise reduction, estimation of the tuning and then represents the track as a succession of chroma vectors over time. The characteristics of the Major and minor modes are learned by training two hidden Markov models on a labeled database. 24 hidden Markov models corresponding to the various keys are then derived from the two trained models. The estimation of the key of a music track is then obtained by computing the likelihood of its chroma sequence given each HMM. The system is evaluated positively using a database of European baroque, classical and romantic music. We compare the results with the ones obtained using a cognitive-based approach. We also compare the chroma-key profiles learned from the database to the cognitive-based ones.
Download Onset Detection Revisited Various methods have been proposed for detecting the onset times of musical notes in audio signals. We examine recent work on onset detection using spectral features such as the magnitude, phase and complex domain representations, and propose improvements to these methods: a weighted phase deviation function and a halfwave rectified complex difference. These new algorithms are compared with several state-of-the-art algorithms from the literature, and these are tested using a standard data set of short excerpts from a range of instruments (1060 onsets), plus a much larger data set of piano music (106054 onsets). Some of the results contradict previously published results and suggest that a similarly high level of performance can be obtained with a magnitude-based (spectral flux), a phase-based (weighted phase deviation) or a complex domain (complex difference) onset detection function.
Download A New Analysis Method for Sinusoids+Noise Spectral Models Existing deterministic+stochastic spectral models assume that the sounds are with low noise levels. The stochastic part of the sound is generally estimated by subtraction of the deterministic part: It is assumed to be the residual. Inevitable errors in the estimation of the parameters of the deterministic part result in errors – often worse – in the estimation of the stochastic part. We propose a new method that avoids these errors. Our method analyzes the stochastic part without any prior knowledge of the deterministic part. It relies on the study of the distribution of the amplitude values in successive short-time spectra. Computations of the statistical moments or the maximum likelihood lead to an estimation of the noise power density. Experimentations on synthetic or natural sounds show that this method is promising.
Download Adaptive Noise Level Estimation We describe a novel algorithm for the estimation of the colored noise level in audio signals with mixed noise and sinusoidal components. The noise envelope model is based on the assumptions that the envelope varies slowly with frequency and that the magnitudes of the noise peaks obey a Rayleigh distribution. Our method is an extension of a recently proposed approach of spectral peak classification of sinusoids and noise, which takes into account a noise envelope model to improve the detection of sinusoidal peaks. By means of iterative evaluation and adaptation of the noise envelope model, the classification of noise and sinusoidal peaks is iteratively refined until the detected noise peaks are coherently explained by the noise envelope model. Testing examples of estimating white noise and colored noise are demonstrated.
Download Categories of Perception for Vibrato, Flange, and Stereo Chorus: Mapping Out the Musically Useful Ranges of Modulation Rate and Depth for Delay-Based Effects Vibrato, Flange, and Stereo Chorus are perhaps the three most often used digital audio effects that are created by smoothly modulating the duration of a delay line at typically sub-audio rates. Common practice is to use a periodic or quasi-periodic modulation control signal with frequency roughly between 2 and 9 Hz, and both the rate and depth of delay modulation are typically adjusted according to the aesthetic criteria of a performer or by an audio production engineer. In order to establish norms for the musically useful range of modulation rate and depth for such delay-based effects, 25 listeners were asked to make categorical judgments regarding their perception of vibrato, flange, and stereo chorus effects. The results map out for these two modulation parameters three perceptual regions for these three related effects: the region in which modulation is too subtle for effective use, the parameter ranges that seem most musically useful, and the region in which it is too extreme for most musical applications. Of particular interest is the observed commonality between these perceptual regions for vibrato, flange, and stereo chorus effects.