Active control of transformer noise radiated outside a three-dimensional building with one opening

Previous work has demonstrated that active noise control (ANC) is an effective method to re-duce transformer noise. The transformer is sometimes placed inside a building with one opening, and the performance of the ANC system is investigated both numerically and expe-rimentally. The simulation results show that the noise reduction of the 15-channel active noise control system can be up to 12.4 dB for 100 Hz and 4.9 dB for 200 Hz when the inter-val between secondary sources is about half the wavelength of 200 Hz and the error micro-phones are placed about 20 cm in front of the corresponding secondary sources. A virtual sound barrier is implemented on the opening of the building to investigate the actual perfor-mance of the system, and the noise reduction achieved in the experiments under the same configuration as in simulations is 15 dB for 100 Hz and 8 dB for 200 Hz in the far field. Both the simulation and experiment results prove that implementing the virtual sound barrier is an effective way to control transformer noise radiated outside the opening of a three-dimensional building