Improving acoustic wave propagation models in highly attenuating porous materials

Area of Science:

• Acoustics
• Materials Science
• Wave Propagation

Background:

• The Johnson-Champoux-Allard model, while common, struggles with accurately predicting acoustic wave propagation in highly absorbent porous materials at high frequencies.
• Accurate modeling of acoustic attenuation is vital for developing effective noise reduction solutions, particularly in automotive applications using plastic foams.
• Existing models fail to reconstruct transmitted acoustic signals in materials with significant wave attenuation within the airborne ultrasonic frequency range (30–200 kHz).

Purpose of the Study:

• To present an improved and extended modeling approach for acoustic wave propagation in rigid porous materials.
• To address the limitations of classical models in accurately describing wave attenuation in highly absorbent media.
• To enable more comprehensive characterization of porous materials for advanced noise reduction applications.

Main Methods:

• Introduced new non-acoustic parameters (Σ, V for viscous effects; Σ', V' for thermal effects) with surface and volumetric dimensions.
• Incorporated these parameters into the expansion on skin depths of dynamic tortuosity α(ω) and thermal tortuosity α'(ω) response functions.
• Validated the model's ability to reconstruct transmitted acoustic signals and model pronounced acoustic attenuation.

Main Results:

• The novel modeling approach successfully reconstructs the transmitted acoustic signal, outperforming classical models.
• Accurate modeling of pronounced acoustic attenuation within high-attenuating porous materials was achieved.
• The extended model provides a more comprehensive understanding of fluid-solid interactions (inertial-viscous and thermal).

Conclusions:

• The improved model accurately describes acoustic wave propagation and attenuation in highly absorbent porous materials at ultrasonic frequencies.
• This approach enhances the capability for characterizing complex porous media, crucial for effective noise reduction technologies.
• The study opens new avenues for material characterization beyond the scope of current acoustic models.