Describing and classifying urban sound environments with a relevant set of physical indicators.

Categorization is a powerful method for describing urban sound environments. However, it has only been applied, until now, to discrete noise data collection, whereas sound environments vary continuously both in space and time. Therefore, a procedure is developed in this paper for describing the variations of urban sound environments. The procedure consists of mobile measurements, followed by a statistical clustering analysis that selects relevant noise indicators and classifies sound environments. Analysis are based on a 3 days + 1 night survey where geo-referenced noise measurements were collected over 19 1-h soundwalk periods in a district of Marseille, France. The clustering analysis showed that a limited subset of indicators is sufficient to discriminate sound environments. The three indicators that emerged from the clustering, namely, the Leq, A, the standard deviation σL eq, A, and the sound gravity spectrum SGC[50 Hz-10 kHz], are consistent with previous studies on sound environment classification. Moreover, the procedure proposed enables the description of the sound environment, which is classified into homogenous sound environment classes by means of the selected indicators. Thus, the procedure can be adapted to any urban environment, and can, for instance, favorably enhance perceptive studies by delimiting precisely the spatial extent of each typical sound environment.

Numerical study of the impact of vegetation coverings on sound levels and time decays in a canyon street model.

Given a constantly increasing urban population, the mitigation of environmental impacts caused by urbanization has become a critical concern. Sprawling cities accelerate the phenomenon of soil sealing, whose impacts relative to climatology, water cycle and ecology are substantial. The "VegDUD" project, which provides the framework for the present paper, lays out a possible alternative for limiting these deleterious effects through focusing on the role of vegetation in promoting sustainable urban development. The study presented herein addresses the beneficial effect of greening building facades and rooftops in terms of both acoustic level and sound-decay time indicators at low frequency third-octave bands. This is carried out through numerical simulations in the time-domain of sound propagation in a canyon street of infinite length for various scenarios of surface vegetalization. Numerical predictions show a more significant effect in the upper part and outside the street, depending on the location of the vegetalized surfaces, frequency bands and number of reflections on the treated materials.

Color-changing and color-tunable photonic bandgap fiber textiles.

We present the fabrication and use of plastic Photonic Band Gap Bragg fibers in photonic textiles for applications in interactive cloths, sensing fabrics, signage and art. In their cross section Bragg fibers feature periodic sequence of layers of two distinct plastics. Under ambient illumination the fibers appear colored due to optical interference in their microstructure. Importantly, no dyes or colorants are used in fabrication of such fibers, thus making the fibers resistant to color fading. Additionally, Bragg fibers guide light in the low refractive index core by photonic bandgap effect, while uniformly emitting a portion of guided color without the need of mechanical perturbations such as surface corrugation or microbending, thus making such fibers mechanically superior to the standard light emitting fibers. Intensity of side emission is controlled by varying the number of layers in a Bragg reflector. Under white light illumination, emitted color is very stable over time as it is defined by the fiber geometry rather than by spectral content of the light source. Moreover, Bragg fibers can be designed to reflect one color when side illuminated, and to emit another color while transmitting the light. By controlling the relative intensities of the ambient and guided light the overall fiber color can be varied, thus enabling passive color changing textiles. Additionally, by stretching a PBG Bragg fiber, its guided and reflected colors change proportionally to the amount of stretching, thus enabling visually interactive and sensing textiles responsive to the mechanical influence. Finally, we argue that plastic Bragg fibers offer economical solution demanded by textile applications.