# Hybrid Helmholtz–Helical Metamaterial for Broadband-Targeted Suppression of Substation Noise

## TL;DR

A new metamaterial is developed to effectively absorb low-frequency noise from electrical substations, offering a promising solution for noise control and environmental protection.

## Contribution

A novel hybrid Helmholtz–Helical metamaterial is introduced, optimized with a genetic algorithm for broadband low-frequency noise suppression.

## Key findings

- The metamaterial achieves high absorption coefficients exceeding 0.9 at target frequencies (100 Hz, 300 Hz, and 500–1300 Hz).
- 3D-printed samples validated the design's effectiveness in suppressing low-frequency substation noise.
- The structure shows potential for broader applications in urban noise mitigation and environmental protection.

## Abstract

Low-frequency noise, primarily generated by transformers and electrical machinery in substations, presents considerable environmental and health risks due to its strong penetration and minimal attenuation. Conventional noise control methods often fail to effectively absorb such low-frequency sounds. In response to this challenge, acoustic metamaterials featuring unique subwavelength structures have emerged as a promising solution for absorbing low-frequency and broadband noise. This study introduces a novel sound-absorbing metamaterial that integrates parallel-connected Helmholtz resonators with a helical cavity structure. To enhance its performance across a broad frequency range, the metamaterial is optimized using a genetic algorithm. Experimental validation, based on 3D-printed samples and impedance tube measurements, demonstrates high absorption efficiency at target frequencies (100 Hz, 300 Hz, and 500–1300 Hz), with absorption coefficients exceeding 0.9. The results confirm that the metamaterial effectively reduces low-frequency core noise. This work represents a significant advancement in noise control technologies for substations, with broader implications for urban noise mitigation and environmental protection.