Within solid acoustics and condensed matter physics, the propagation characteristics of elastic waves within materials reflect microscopic elastic moduli, density distributions, and internal energy dissipation states. When ultrasonic waves traverse the three-dimensional porous networks of aerogels—characterized by high porosities and interconnected nanoscale particles—their propagation behavior deviates from that observed in dense bulk media. The complex micro-topological structures, narrow skeletal necks, and abundant gas-solid interfaces within aerogels act as multiple scattering centers and viscoelastic damping barriers, inducing significant acoustic velocity dispersion and phonon group velocity attenuation.

From an acoustic physics perspective, when high-frequency ultrasonic waves propagate through aerogel porous media, the mechanical vibration energy couples with the solid skeleton and interstitial gases. Because the solid framework consists of amorphous nanoparticles linked by narrow neck regions, local elastic stiffness exhibits spatial fluctuations. When ultrasonic wavelengths approach characteristic pore dimensions, classical continuum acoustics approximations fail, and waves undergo Mie and Rayleigh scattering.

This scattering causes phase and group velocities to exhibit frequency-dependent variations, known as velocity dispersion. High-frequency components encountering impedance mismatches experience energy conversion into thermal dissipation. Furthermore, microscopic sliding friction along polymer segments or inorganic surfaces provides viscoelastic damping. Investigating velocity dispersion and phonon dissipation clarifies acoustic behaviors in porous media.