Acoustic radiation from multilayered materials using the reciprocity principle

Area of Science:

• Acoustics
• Materials Science
• Fluid Dynamics

Background:

• Acoustic radiation from multilayered materials is crucial for understanding sound propagation and noise generation.
• Existing models often simplify surrounding media or material properties, limiting applicability.
• Incorporating shear motion and fluid viscosity is essential for accurate acoustic analysis.

Purpose of the Study:

• To develop a comprehensive method for evaluating acoustic radiation from arbitrary multilayered fluid and solid materials.
• To incorporate the effects of shear motion and fluid viscosity in the surrounding medium.
• To analyze acoustic radiation under point force excitation for various material configurations and excitation conditions.

Main Methods:

• Application of the reciprocity principle to derive equations for acoustic radiation.
• Development of equations using reflection and transmission coefficients for longitudinal and shear waves.
• Calculations performed for asymmetric layer arrangements, arbitrary forcing directions, and frequencies beyond thin/thick plate limitations.

Main Results:

• Quantified the significant impact of viscosity and attenuation on acoustic radiation at high frequencies.
• Demonstrated the method's capability to handle complex multilayered structures and surrounding media.
• Investigated the acoustic radiation from plates embedded in viscous and attenuating fluids as a detailed test case.

Conclusions:

• The developed reciprocity-based method accurately evaluates acoustic radiation from multilayered materials, including shear effects and fluid viscosity.
• Viscosity and attenuation play a critical role in high-frequency acoustic radiation, particularly for embedded structures.
• The findings have implications for understanding and mitigating flow noise in various engineering applications.