Internal acoustic resonances: small scattering center compared with the wavelength

Abstract: In fields such as acoustics, electromagnetism, and quantum physics, the scattering of waves by localized objects is a fundamental phenomenon. Building on this, the present study investigates the energy distribution within a spherical scattering center during its interaction with an incident acoustic wave. The analysis reveals unexpected resonance effects driven by impedance mismatches between the scattering center and the surrounding ideal fluid. These resonance phenomena occur even when the magnitude order of the incident wavelength is significantly larger compared to the size of the scattering center. Such resonance behavior, observed in the small-particle regime, has potential applications in ultrasound imaging, targeted drug delivery, and metamaterial design.