Sound effect derives a pair of highly loaded machinery parts-motion screw and nut. Loaded pair is used in non-standard environments of high voltage electrical equipment in electrical substations. The non-standard environment is seen in the movement of this pair immersed in transformer oil deeply below the surface. Transformer oil has no good mechanical lubricating properties because it does not contain sulfur. Loaded pair cannot be lubricated, because there would be oil contamination and deterioration of its electro-insulating properties. The causes were sought in the structure of the machine, frame stiffness, mechanical strength machine and used materials. The aim of the research with help experimental and numerical study was to define the cause and eliminate sound effect coming from the device.