Observation of micropolar modes in the transmission of acoustic waves at oblique incidence by polystyrene plates.

This study investigates micropolar plates through the analysis of transmitted acoustic waves at various incident angles. Using a combined theoretical and experimental approach, we explore the non-classical elasto-dynamic behavior of these materials. Theoretical transmission coefficients are tailored to highlight generalized Lamb modes and a new type of vibration mode called micropolar modes, considering the constant thickness of the plate and the effects of material micropolarity on linear elasticity.

Improving acoustic wave propagation models in highly attenuating porous materials.

This article presents an improved and extended modeling approach for acoustic wave propagation in rigid porous materials, focusing on examples, such as plastic foams used for noise reduction in automotive applications. We demonstrate that the classical model (Johnson-Champoux-Allard) in the asymptotic high-frequency limit, widely employed in the literature, fails to accurately reconstruct the transmitted acoustic signal through high absorbent porous materials characterized by significant wave attenuation. The study focuses on the airborne ultrasonic frequency range (30-200 kHz).

Fractal Analysis of a Non-Newtonian Fluid Flow in a Rough-Walled Pipe.

The fully developed laminar flow of a viscous non-Newtonian fluid in a rough-walled pipe is considered. The fluid rheology is described by the power-law model (covering shear thinning, Newtonian, and shear thickening fluids). The rough surface of the pipe is considered to be fractal, and the surface roughness is measured using surface fractal dimensions.

Analysis of the Acoustic Transcranial Bone Conduction.

Objectives: (1) To analyze the preferential pathways of sound transmission and sound waves travelling properties in the skull and (2) to identify the location(s) on the skull where bone conduction to the cochlea is optimal.

Study Design: Basic research Methods: Nine cadaveric heads were placed in an anechoic chamber and equipped with six Bone Anchored Hearing Aids (BAHA™) implants (Cochlear™, Sydney, NSW, Australia) and fifteen accelerometers. A laser velocimeter was used to measure cochlear response by placing a reflector on the round window.

Influence of Higher Order Viscous and Thermal Effects on an Ultrasonic Wave Reflected from the First Interface of a Porous Material.

Ultrasound propagation in porous materials involves some higher order physical parameters whose importance depends on the acoustic characteristics of the materials. This article concerns the study of the influence of two parameters recently introduced, namely, the viscous and thermal surfaces, on the acoustic wave reflected by the first interface of a porous material with a rigid structure. These two parameters describe the fluid/structure interactions in a porous medium during the propagation of the acoustic wave in the high-frequency regime.