Whats is the reason for clicking (fan)?

Now I'm not talking about clicking when a fan is receiving too little voltage to rotate. I'm talking about like my Mechatronics fans, which when above a certain voltage level (I'd say 40%+), I hear a clicking sound, almost like a buzzing. I'm guessing its the electricity in the motor itself, but I dont know why it makes that sound in the first place. And do other fans suffer from the same electrical noise, or is it because of the way the motor is made?

Some fans dislike being run on a PWM fan controller. Thats one reason why it could be clicking. To fix it, get a rheostat based fan controller for it or replace the fan. Also you may need to lubricate the fan bearings.

I'm using a Zalman Fanmate2 on the Mechotronic, so its a rheo controller.

Could be the bearings, as this fan uses bearings. Its not that old, but had been sitting for a number of months unused. It does change in pitch and volume as the fan spins faster, but at its lowest setting, the sound is inaudible to me.

The clicking is a result of the frequency of the signal sent to the fans motor.

SPCR said:

The stator motion is a square wave that is switched on and off before and after the peak torque position. This motion causes a small amount of undulation in motor torque, producing an audible noise caused by the lower frequency commutation operation. Each small torque causes a minute contracting of the entire fan structure and results in an audible clicking noise while the fan is operating.

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