Direct Measurement of Acoustic Spectral Density and Fractional Topological Charge

LDOS is a fundamental spectral property that plays a central role in various physical phenomena, such as wave-matter interactions and spontaneous emissions. The role of LDOS in acoustics was uncovered only in recent years and the measurement of acoustic LDOS has not yet been achieved. Here, we report on the direct measurement of the LDOS in acoustic systems. The acoustic LDOS is quantified here through the measurement of the volume flow rate and the acoustic pressure with a local excitation-probe configu-ration. Based on this method, we detect the LDOS in the one-dimensional acoustic Su-Schrieffer-Heeger model and observe the fractional topological charge of the system. Our work unveils the role of the LDOS in acoustic phenomena and paves the way toward characterizing and tailoring the LDOS in acous-tic systems, which holds promise for applications in acoustic emission control, energy localization, and wave-matter interaction.

Automated summary

This study reports on the direct measurement of the local density of states (LDOS) in acoustic systems. The LDOS in acoustics is quantified through the measurement of volume flow rate and acoustic pressure. The results unveil the role of LDOS in acoustic phenomena and pave the way for controlling and characterizing LDOS for various applications in acoustic emission control, energy localization, and wave-matter interaction.