La transmission de l'energie sonore dans les salles

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Urban Soundscapes in the Imaginaries of Native Digital Users: Guidelines for Soundscape Design

We present an experiment run along the lines of a pilot experiment in China based on collages and narratives to illustrate the participants’ experience with urban sceneries. Its aim was to develop a conceptual model based on narrative analysis that linked objects of the environment to the perceived properties of the soundscape. Participants in groups of two were free to clip any image they wanted from a selection of magazines—the same for all groups within each country—and free to add comments or drawings on their collages. Then, they had to present their collages to the other participants, and the presentations were recorded and transcribed. The structural semantic model that underlies the descriptions of the collages and narratives is presented. The results of the analysis were comparable with previous studies, since ideal urban environments should be calm, quiet and green, but urban environments should also promote cultural activities and the possibility to escape outside the city. The analysis also allowed for attaining the emotions created by soundscapes. Thus, the semantic model can be used as a conceptual model for a soundscape, from which guidelines for soundscape planning and design can be derived, as well as suggestions for innovative soundscapes

Generalized formulation for acoustics

In 1937, Janowski and Spandöck (Akust. Z., 2:322–331) experimentally demonstrated the curvature of sound rays travelling at grazing incidence above absorbing materials. 30 years later, Cremer and Müller (Die wissenschaftlichen Grundlagen der Raumakustik, Band II, Hirzel Verlag, 1978) showed that this curvature was created by the surface admittance of the material; however, they were not able to demonstrate the curvature of the rays. By making use of the stress-energy tensor, introduced in Acoustics by Morse and Ingard (Theoretical Acoustics. Mc Graw-Hill, 1968), we show that this formalism, borrowed from the general relativity theory, makes it possible to derive the curvature of grazing rays, provided that general coordinates are adopted so that the metric tensor adapts itself to the admittance at the boundary. We show that the metric tensor can be arbitrarily defined, with the only condition that the normal derivative of the velocity potential be null. Absorption is then taken into account by the residual Christoffel symbols that define normal derivation of the stress-energy tensor at the boundary. A generalized formulation of energy conservation is then obtained, which generalizes earlier work on energy propagation in corridors and flat rooms by Dujourdy et al. (Acta Acustica, 103:480-491, 2019; Wave Motion 87:193-212, 2019). An unexpected result from the formalism is that the imaginary, or reactive, part of the stress-energy tensor satisfies Maxwell equations