psu making buzzing sounds

My ax760 is making a sort of high pitch buzzing noise sounds like the noise you hear from the small power substations on the street except ita more higher pith then the lower pitch transformer hum. The fan is in hybrid mode on not turning. I removed the psu from my case

Put my ear against it to verify the source of sound then powered the pc. It is definitely coming from the psu. The buzzing noise seems to vary with load. When the pc is powered off the buzzing goea away. What could this be?