Sound-absorbing coatings with nonlinear elastic modulus

Area of Science:

• Acoustics
• Materials Science
• Nonlinear Dynamics

Background:

• Cavity-type underwater anechoic coatings are crucial for reducing acoustic signatures.
• Existing linear models struggle to accurately predict sound absorption under varying conditions.
• Material nonlinearity significantly impacts acoustic performance but is often overlooked.

Purpose of the Study:

• To develop and validate a nonlinear model for cavity-type underwater anechoic coatings.
• To investigate the influence of acoustic frequency and incident sound pressure on sound absorption.
• To enhance the prediction accuracy of sound absorption coefficients compared to linear models.

Main Methods:

• A nonlinear model incorporating a complex Young's modulus dependent on acoustic frequency and sound pressure was proposed.
• The Kraus model was used to represent the nonlinear modulus, with parameters derived from Dynamic Mechanical Analysis data.
• Iterative calculations using the Newton-Raphson method determined absorption results.
• The transfer matrix method was used for validation at low incident sound pressures.

Main Results:

• The nonlinear model accurately predicts enhanced and shifted resonance peaks in sound absorption coefficients.
• Increasing incident sound pressure shifts resonance peaks to lower frequencies.
• Frequency dependence shifts resonance peaks to higher frequencies.
• The nonlinear model reduced prediction errors by 33.0% to 55.9% compared to linear models.

Conclusions:

• Material nonlinearity significantly improves the prediction accuracy of sound absorption in underwater anechoic coatings.
• The proposed nonlinear model offers a more reliable approach for designing and evaluating anechoic materials.
• The findings highlight the importance of considering material nonlinearity for accurate acoustic performance prediction.