A natural ventilation window for transformer noise control based on coiled-up silencers consisting of coupled tubes

For transformers located inside rooms, openings in the walls are often required for ventilation and heat dissipation with the result that transformer noise radiates to the outside. A soundproof window for indoor transformers is proposed in this paper, which provides both air circulation and noise reduction simultaneously. A silencer consisting of two coupled tubes with different cross sections is designed and coiled up in space to minimize the thickness of the structure. With carefully chosen parameters, just one such silencer can achieve sound attenuation at up to 4 frequencies. With a combination of a staggered window and specially designed silencers, effective noise reduction is obtained at 100 Hz, 200 Hz, 300 Hz, 400 Hz and 500 Hz, where harmonic components contribute the most to the transformer noise. The experimental results with a 1:4 scale down model show the feasibility of the proposed design.