Angular control of the sound radiation can be achieved by using a compact array of independently programmable loudspeakers operating at the same frequency range. The drivers are usually distributed over a sphere-like frame according to a Platonic solid geometry to obtain a highly symmetrical configuration. Prototypes of compact spherical loudspeaker arrays have been recently developed and applied in room acoustics measurements, electroacoustic music performance and synthesis of directivity patterns of acoustical sources such as musical instruments. However, many aspects concerning their control, design, electromechanical behavior and ability to provide a more realistic sound experience than conventional audio systems remain unclear. This work concerns the analysis and synthesis of sound fields by a compact spherical loudspeaker array and aims to contribute to clarifying some aspects mentioned above. A control strategy based on the acoustic radiation modes of the spherical array is proposed, which presents several advantages over the usual strategy based on the spherical harmonics. A theoretical and experimental analysis of the electromechanical behavior of compact loudspeaker arrays is also presented, in which the acoustic coupling between drivers inside the array frame is taken into account. In addition, optimum driver signals corresponding to a given target directivity pattern are derived using two different cost functions, indicating that the realism of the synthesized pattern may be significantly increased by neglecting the phase of the target directivity pattern. Finally, the proposed theoretical models are validated through measurements of electrical impedance, loudspeaker diaphragm velocity and directivity patterns.

L'auto-organisation des organismes vivants est d'une complexité et d'une efficacité étonnantes. Plus précisément, les systèmes biologiques abritent un nombre gigantesque de réactions très spécifiques qui nécessitent que la bonne biomolécule se retrouve à la bonne place, dans le bon ordre et en un temps suffisamment court pour permettre le fonctionnement cellulaire, et au-delà la vie cellulaire. D'un point de vue dynamique, cela pose la question fondamentale de savoir comment les biomolécules trouvent efficacement leur(s) cible(s) spécifique(s), ou encore, quels types de forces rassemblent tous ces partenaires de réaction spécifiques dans un environnement aussi dense et ionisé que les micro-environnements cellulaires. Dans cette thèse, nous explorons la possibilité que des biomolécules puissent interagir à travers des interactions électromagnétiques de longue-portée telles que ces dernières sont prédites à partir des premiers principes de la physique; ''longue-portée'' signifiant que les interactionsen question sont actives sur des distances bien plus larges que les dimensions typiques des molécules mises en jeu (i.e., plus grandes qu'environ 50 angströms dans les systèmes biologiques). Après avoir posé les fondements théoriques concernant les interactionsde longue-portée potentiellement actives sur de longue distances dans un contexte biologique, nous étudions la posssibilité de détecter leur éventuelle contribution à partir de dispositifs expérimentaux qui sont accessibles de nos jours. Sur ce dernier point, des résultats préliminaires encourageants tant sur le plan théorique qu'expérimental sont présentés. / Self-organization of living organisms is of an astonishing complexity and efficiency. More specifically, biological systems are the site of a huge number of very specific reactions thatrequire the right biomolecule to be at the right place, in the right order and in a reasonably short time to sustain cellular function and ultimately cellular life. From the dynamic point of view, this raises the fundamental question of how biomolecules effectively find their target(s); in other words, what kinds of forces bring all these specific cognate partners together in an environment as dense and ionized as cellular micro-environments. In the present thesis, we explore the possibility that biomolecules interact through long-range electromagnetic interactions as they are predicted from the first principles of physics; "long-range" meaning that the mentioned interactions are effective over distances much larger than the typical dimensions of the molecules involved (i.e., larger than about 50 angströms in biological systems).After laying the theoretical foundations about interactions that are potentially active over long distances in a biological context, we investigate the possibility of detecting their contribution from experimental devices which are nowadays available. On the latter point, encouraging preliminary results both at the theoretical and experimental levels are exposed.