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Press release
Acoustical absorption of irregularly shaped objects | |||
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Paris, October 24, 2002 |
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| Fundamental
research on irregularly shaped objects has led to the development of new
types of high-performance road noise barriers. In conjunction with the firm
Colas, a patent was filed and the barrier design, now entering production,
has demonstrated as yet unequaled noise absorption characteristics. Irregularly shaped objects are omnipresent in nature and much has yet to be learned about their vibratory properties: How do trees behave in the wind? How do waves depend on the topography and the geometric structure of the coastline and sea walls? These questions have yet to be thoroughly answered. However, it is known that a small disturbance in the resonator’s geometric shape can almost completely eliminate a resonance phenomenon by augmenting dampening. This has been used, albeit only empirically, in radar technology or in the design of musical instruments. Recent research conducted by the team of B. Sapoval(1) (CNRS, Ecole polytechnique, ENS Cachan) has focused on the dampening capacity of resonators with an irregular geometric shape or isolated defects(2). To model these shapes, physicists use the principles of fractal geometry. Consequently, they show that fractal “drums” and acoustical cavities (the word drum indicates a structure that can resonate like a drum) and, more generally, resonator with a “ragged” or “jagged” shape can, in certain cases, possess dampening qualities that surpass conventional systems with a smooth or regular geometric shape. (1) O. Haeberlé, B. Hébert, S. Russ and M. Filoche ("Physique de l'irrégularité" Group, Laboratoire de physique de la matière condensée, Unité mixte CNRS-Ecole polytechnique). (2) Journal of the Acoustical Society of America, 105, 1567,1999 and Physical Review E, vol. 65, 036614, 2002 For more information: Bernard Sapoval wrote “Universalités et fractales,” published in Flammarion’s "Champs" collection. Contacts: |
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