Topological Vibroacoustic Metamaterials for Low-Frequency Sound Manipulation at the Subwavelength Scale

The ability to manipulate low-frequency sound is essential due to its significant societal, environmental, and technological implications. Low-frequency sound, characterized by long wavelengths and weak damping, exhibit strong diffraction and penetration, making them persistent and challenging to control. Acoustic metamaterials, which typically rely, either directly or indirectly, on Bragg diffraction, require periodic structures on scales comparable to the wavelength. This restricts their application to ultrasonic frequencies or necessitates impractically large structures for audible sound. In this seminar, I will introduce new sub-Bragg mechanisms that address these challenges, including the formation of genuinely subwavelength Bragg-like bandgaps, termed “band-splitting-induced bandgaps”, and the widening of subwavelength local resonance bandgaps by incorporating multiple resonances within the same bandgap.