Making the buzz sound of pulse width modulated fans disappear

[canol]

Hello, I have a circuit which drives several fans using Arduino analog output and a MOSFET (IRFZ44N). The problem is that when I drive these 12V fans at, for example, 5V they make a very noticable and annoying buzz sound. Here is a video on Youtube showing the same sound problem:



I want to make this sound disappear. Would using a motor driver IC instead of driving a MOSFET from Arduino solve the problem? Like for example L293D:

http://www.ti.com/lit/ds/symlink/l293d.pdf

Or are there other ways to do it?

[matkar]

One way is to use linear control. Downside are greater losses on the transistor, the positive side is the revolutions feedback wire gives exact RPMs.
The other way is to increase PWM frequency to get above audible frequencies.

[dc101]

I can't tell from your video, but if you're not using it already, you need a low-pass filter on your PWM output.  Check out this link http://provideyourown.com/2011/analogwrite-convert-pwm-to-voltage/

[TerminalJack505]

How embarrassing.     LOL.  That's my video.

I was going to build a fan controller at one time and never did.  I had heard about the noise that could be produced if you use PWM.  At the time I couldn't find a video that demonstrated the noise so I decided to make my own.

In addition to what's been suggested here, you might try a lower PWM frequency.  A couple hundred Hertz or less.  Supposedly, the noise is less noticeable.

A switching regulator is another idea.

If you go the route of using PWM at a frequency beyond the audible range then you'll likely have to put a fast-decay snubber across the fan's terminals.  Otherwise the current will just 'freewheel' and the fan's speed will no longer be a (roughly) linear function of the PWM duty cycle.

[rdl]

This may be helpful:

Suppressing Acoustic Noise in PWM Fan Speed Control Systems

[David Hess]

Keep in mind that the fan uses a DC brushless motor and its electronic commutation circuit is designed to work with a steady DC source although at low DC voltages, it may become noisy anyway.

An LC filter on the output of the pulse width modulator like you would find on a buck switching regulator will solve this problem.

[Zero999]

I can't tell from your video, but if you're not using it already, you need a low-pass filter on your PWM output.  Check out this link http://provideyourown.com/2011/analogwrite-convert-pwm-to-voltage/

A simple RC filter is only useful for low current signals.

For higher currents, you need an inductor as well as a capacitor.

[canol]

Thank you very much for your responses.