Explicit Mapping of Acoustic Regimes For Wind Instruments

This paper proposes a methodology to map the various acoustic regimes of wind instruments. The maps can be generated in a multi-dimensional space consisting of design, control parameters, and initial conditions. The bound- aries of the maps are obtained explicitly in terms of the parameters using a support vector machine (SVM) classifier as well as a dedicated adaptive sam- pling scheme. The approach is demonstrated on a simplified clarinet model for which several maps are generated based on different criteria. Examples of computation of the probability of occurrence of a specific acoustic regime are also provided. In addition, the approach is demonstrated on a design optimization example for optimal intonation

SVM CLASSIFICATION OF QUASI-PERIODIC REGIMES OF SINGLE REED INSTRUMENTS

International audienceSingle-reed instruments can produce multiphonic sounds when they generate quasi-periodic oscillation regimes. An approach to map the periodic and quasi-periodic regimes of a wind instrument is presented. The mapping is performed using an SVM classifier trained using the output of a simplified single-reed instrument model. The SVM classifier is iteratively refined using an adaptive sampling scheme referred to as Explicit Design Space Decomposition. This method provides the explicit boundaries separating quasi-periodic and periodic regimes and highlights the influence of key parameters involved in the production of multiphonic sounds

OPTIMIZATION UNDER UNCERTAINTY OF NONLINEAR ENERGY SINKS

ABSTRACT Nonlinear Energy Sinks (NES) are used to passively reduce the amplitude of vibrations. This reduction is made possible by introducing a nonlinearly stiffening behavior in the NES, which might lead to an irreversible transfer of energy between the main system (e.g., a building) and the NES. However, this irreversible transfer, and therefore the efficiency of the NES, is strongly dependent on the design parameters of the NES. In fact, the efficiency of the NES might be so sensitive to changes in design parameters and other factors (e.g., initial conditions) that it is discontinuous, switching from efficiency to inefficiency for a small perturbation of parameters. For this reason, this work introduces a novel technique for the optimization under uncertainty of NES. The approach is based on a support vector machine classifier, which is insensitive to discontinuities and allows one to efficiently propagate uncertainties. This enables one to efficiently solve an optimization under uncertainty problem. The various techniques presented in this paper are applied to an analytical * Address all correspondence to this author. NES example. INTRODUCTION Nonlinear Energy Sinks (NES) have become a promising approach for the reduction of vibration

Woodwind instrument design optimization based on impedance characteristics with geometric constraints

International audienceComputational optimization algorithms coupled with acoustic models of wind instruments provide instrument makers an opportunity to explore new designs. Specifically, they give the possibility to automatically find geometries exhibiting desired resonance characteristics. In this paper, the design optimization of woodwind instruments with complex geometrical features (e.g., non-cylindrical bore profile and side holes with various radii and chimney heights) is investigated. Optimal geometric characteristics are searched to obtain specific target frequencies or amplitude characteristics. However, woodwind instruments exhibit complex input impedance whose features might change drastically for a small variation of the geometry, thus hampering gradient-based optimization. For this reason, this paper introduces new formulations of the impedance characteristics (resonance frequencies and amplitudes). The approach is applied to an illustrative instrument subjected to geometric constraints similar to the ones encountered by manufacturers (a key-less pentatonic clarinet with two-registers). Three optimization problems are considered, demonstrating a strategy to simultaneously adjust several impedance characteristics on all the fingerings

EXPLICIT MAPS OF ACOUSTIC REGIMES OF A WIND INSTRUMENT

International audienceAn approach to map the various acoustic regimes of a wind instument is presented. In this work, the regimes are first classified based on the occurence or the lack of sound. Physically, the production of a sound corresponds to the existence of self-sustained oscillations in the resonator of the instrument, whereas the lack of sound is associated with a stable static regime. Another classification based on the sound frequency is also investigated. The maps are created in a space consisting of design and control parameters. The boundaries of the maps are obtained explicitly in terms of the parameters using a support vector machine classifier as well as a dedicated adaptive sampling scheme. The approach is applied to a simplified clarinet model