what's the reason for this noise in the SMD transformer
It's really quite a bad idea to put a powerful magnet on those transformers, especially the larger one, you can destroy the power supply. I don't see any SMD transformers there, the smaller one looks like a drive transformer. 

The noise might be coming from the coil or from nearby capacitors. You can try painting the coil with some insulating lacquer, or just put the board in a box. Ideally the transformers are vacuum impregnated during the manufacturing process.