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This sounds an abnormal question at first, but I really would like to know how to make a normal table fan noisy (which parts to change). The reason why I want the noise is that the noise from the table fan is kind of white (distributed all over the frequency), that it hides the other noise. I have a busy street near my house. Of course, I could use a white noise generator but I also got some disturbing mosquitoes that needs to be blown away.

Thank you

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  • Not a direct answer to your question - but you might want to look into noise-cancelling headphones.
    – Mike Baranczak
    Apr 6 '20 at 14:17
  • @MikeBaranczak Thanks for the suggestion, but I don't use headphones much, the electronics tend to cause headache and heat. In addition, during sleeping, it becomes very uncomfortable.
    – sundar
    Apr 7 '20 at 9:56
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    Stick a couple zip ties in the fan so as it spins it makes a ticking noise 😏
    – hello moto
    Apr 7 '20 at 18:54
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I use my fan for this very reason. 'Fortunately' mine makes enough noise that simply turning it up to high works well enough so I use the fan speed and location within the house to fine tune things to my needs.

White noise from the fan is caused by the sound of air movement, especially turbulent air flow as it moves around items and itself in a pattern much like river rapids. What will tend to cause more of that is inefficiencies in the air flow. The primary items interacting with the air flow is the blades of the fan. Therefore to create more white noise, I suggest roughing up the surface of the blades so that it creates more turbulence.

The front edge of the blades is what hits the air first while the face of the blade is in contact with the air much longer. I would expect that roughing up the front edge would tend to create more loudness while roughing up the blade face would create more white-ish noise.

This could be done permanently by marking up the blades with something like sandpaper, or a grinder, or a razor knife. To do temporary, which also allows for more adjustment and experimentation, you can add tape, or even better, hot glue melt pieces on in a 'bumpy' pattern on the surface of the blades.

Note that this will be adding weight to the blades and we want to add weight to each blade evenly to keep the overall rotating fan in balance. When out of balance it will wobble and and likely make undesirable non-white noise, and tend to wear out the fan much faster due to stress on the bearings.

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  • Changing lambda would create more noise especially if you go above M=1...
    – Solar Mike
    Apr 6 '20 at 14:22
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    I think this answer best addresses the practical question at hand. As for implementation, I would experiment with tape applied like _|\_|\_|\_ symmetrically to the blades. Drilling holes in the blades could also work.
    – ShapeOfMatter
    Apr 6 '20 at 14:27
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A piece of sticky tape on one blade so it taps the grill will work.

Probably will need replacing every so often, try lighter or heavier tape and see.

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  • @Ack so get a mic and , in real time, invert the input - much like the headsets used in jet fighter helmets to reduce the ambient noise, cost no object.
    – Solar Mike
    Apr 6 '20 at 14:00
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    Yeah, like playing cards in the frames of bicycles so they hit the spokes. Does anyone even remember doing that these days?
    – Carl Witthoft
    Apr 6 '20 at 18:02
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Interesting! Some ideas you could try

  • Put a damp (not dripping wet!) cloth over the top of the fan, this might make it work a little bit harder and therefore generate more noise. I see this suggestion a lot as a makeshift air conditioner.
  • Similar to above, I wonder if taping some paper or something else light weight over the fan,or in front of the fan, you might get some noise from the wind turbulence on the paper which will be broadband-ish (if you the paper is held in place quite tight rather than flapping about all over the place. Thinking about it, a light metal baking tray in front of the fan could be great, or something wrapped in tin foil.
  • Loosen some of the nuts and bolts around the casing of the fan. When they're slightly looser they will be more prone to rattling/vibrating. One bolt rattling is annoying, but all of them rattling might be quite broadband. Probably don't loosen the screws around the fan mechanism itself...
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    Wet cloth over an electrical item? Think again!
    – Tim
    Apr 6 '20 at 10:29
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    Fans have safety cages around them to prevent bodily harm from the high speed fan blades. Loosening the screws and bolts that hold a fan unit together is a recipe for disaster because vibration may very well cause things to come undone and become very unsafe. Better think again about this idea.
    – Michael Karas ♦
    Apr 6 '20 at 10:38
  • Blocking airflow to a fan can actually make it overheat - they're commonly designed so that air is sucked through the motor area to cool it.
    – Khrrck
    Apr 6 '20 at 20:06
  • I said 'damp' cloth not 'wet' cloth. A lightly damp cloth is fine... a lot of people do this as a makeshift airconditioner. Obviously don't put a dripping wet cloth without wringing it out! Re the nuts and bolts, well clearly if the safety cage falls off then stop the fan! A desktop fan is not going to go flying across the room and chop your arm off in the meantime...
    – ParkerJonesAcoustics
    Apr 7 '20 at 10:14

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