Nonlinear wave propagation through multiple scattering media and virtual time reversal focusing

Area of Science:

• Acoustics
• Nonlinear physics
• Wave propagation

Background:

• Understanding wave behavior in complex media is crucial.
• Nonlinear phenomena and multiple scattering effects are often studied separately.
• Investigating their interaction is key to advancing wave manipulation.

Purpose of the Study:

• To experimentally study ultrasonic nonlinear wave propagation through multiple scattering media.
• To analyze the interplay between nonlinear wave phenomena and multiple scattering.
• To evaluate the applicability of theoretical models like the Lighthill-Westervelt equation.

Main Methods:

• Experimental investigation of ultrasonic nonlinear wave propagation.
• Analysis of scattered fields using cross-correlation techniques (virtual time reversal).
• Estimation of parameters quantifying nonlinearity and scattering.

Main Results:

• Nonlinear ultrasonic waves and their harmonics follow the focal width reduction trend with increasing medium thickness.
• The nonlinear regime reduces focal width due to spectral richness.
• Harmonics propagate linearly, despite nonlinear generation.

Conclusions:

• Nonlinear ultrasonic wave propagation in multiple scattering media can be focused.
• Harmonics generated nonlinearly propagate according to linear scattering principles.
• The Lighthill-Westervelt equation accurately models these experimental observations.