Design of a broadband noise reduction barrier utilizing acoustic metamaterial with application to a substation

Power transformer noise in substations is characterized by strong mid-low frequency components below 500 Hz, which are difficult to control using conventional noise barriers. To address this issue, in situ measurements were conducted to identify the acoustic features of transformer noise, and a broadband noise reduction barrier based on Helmholtz resonant absorption was developed. The barrier incorporates parallel Helmholtz resonators with embedded apertures and porous materials to enhance low-frequency energy dissipation and broaden the absorption bandwidth. Reverberation chamber tests and on-site measurements demonstrate that the proposed barrier achieves an average absorption coefficient of 0.80 within the 100–500 Hz in 1/3 octave bands and reduces the outdoor sound pressure level by 12.9 dB at 1 m outside the barrier, outperforming conventional absorbing barriers. The design also allows further performance improvement or thickness reduction through internal parameter optimization, indicating strong potential for practical mid-low frequency noise mitigation in substations.