The transport theory, applied to the concept of sound particles, seems to be well adapted to predict the sound propagation in urban areas, including most complex effects, like diffuse scattering by building facades, atmospheric attenuation, scattering by urban objects in streets, etc. In this paper, the transport theory is then applied to the sound field modeling in an empty street canyon with partially diffusely building facades. In this case, the temporal and spatial distribution of sound energy in a street is the solution of a transport equation, with mixed specular-diffuse boundary conditions. Using an asymptotic approach, the transport equation may be reduced to a diffusion equation for the sound energy, where the diffusion coefficient depends only on the building facades properties. Comparisons with experiments show that the diffusion model gives consistent results with experimental data, both for the sound attenuation level and the reverberation time.
The transport theory of sound particles is applied to the sound field modeling in architectural acoustics. A theoretical description is proposed for empty enclosures with complex boundary conditions, including both specular and diffuse reflections. As an example, the model is applied to street canyons. Therefore, an asymptotic approach is proposed to reduce the transport equation to a diffusion equation defined by only one parameter, the diffusion coefficient. This coefficient is a function of the reflection law of the building façades, the ratio of specular and diffuse reflections, as well as the street width. The model is then compared to Monte Carlo simulations of the propagation of sound particles in complex enclosures. As expected by the asymptotic approach, the model is in agreement with numerical results, but mainly for small street width and very diffuse reflections. Finally, a discussion is proposed in the conclusion, on the model's capabilities.
A new simulation software CRISTA has been developed at LIMSI-CNRS. It is based on the Rott's equations approximation. It computes all thermal and acoustic parameters of a given thermoacoustic device whose geometry is previously designed with another program TADESIGN. To realize the simulation, the user needs only to define a drive ratio at some point of the system and the heat exchanger temperatures. Note that for a prime mover the hot heat exchanger temperature is a simulation result. Every converged solution guarantees the physical principles. Moreover, CRISTA allows computing the quality factor of the resonator. The experimental validations have been successfully performed on different devices coupled to the same prime mover: a simple RLC load, an acoustic amplifier, a pulse tube refrigerator and a lumped boost pulse tube refrigerator.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.