EXPERIMENTAL STUDY ON BROADBAND NOISE SUPPRESSION CHARACTERISTICS OF COMPOSITE OSCILLATOR ARRAY PHONONIC CRYSTALS

In this work, an experimental platform for periodic phononic crystals is utilized to systematically investigate the effects of different parameters on the bandgap characteristics of phononic crystals. This is achieved by testing three types of oscillators: wooden pillars, wooden column-expanded polyethylene (EPE) composites, and EPE hollow cylinders, in combination with two types of periodic arrangements: square and triangular lattices. The experimental results show that the square lattice arrangement of the wooden pillar array significantly broadens the bandgap compared to the triangular lattice arrangement (BG1 bandwidth of 1.2kHz~0.7kHz; BG2 bandwidth of 1.6kHz~0.9kHz). The wooden pillar-EPE composite oscillator extends the high-frequency bandgap to 8kHz (BG2 bandwidth of 4.7kHz) by coupling Bragg scattering and local resonance, while simultaneously improving low-frequency sound absorption efficiency by 20%. This experiment demonstrates broadband noise suppression from 1.3kHz to 8.0kHz in centimeter-scale periodic structures, providing crucial parameter references for the design of phononic crystal noise reduction in transportation and industrial scenarios, such as 1kHz~2kHz mechanical noise and 2kHz~6kHz transformer noise. In addition, the experimental design of this paper can also be incorporated into university physics laboratory teaching as a research-based experiment, helping students to gain a deeper understanding of the concept of band gaps and the importance of physics in engineering applications.