I have created a circuit which implements PWM dimming using phase cutting with Zero cross detection which works well on incandescent bulbs but creates humming noise when connected to a fan. I am using BTA16-800CW (Snubberless triac) to control AC and my triac driver is MOC3023. The ZCD is done using SFH620A-3 opto coupler. I have not connected any snubber / rc filters as BTA16 is mentioned to have it inbuilt. Is the humming expected when doing PWM dimming ? Is there any way to get rid of it ?