Solving fan whine

That could get annoying fast! : )

I'm completely uninformed about fans so I could be totally wrong, but as I understand, sometimes the pressure can result in this, e.g. if the air path is constrained or badly ducted. Or it could just be the fan itself : ) For some products, that are known to be fitted in quiet locations like near people's desks, sometimes a subjective ear-test is also used to rule-in or rule-out fan options during the product development, simply because the fan whine might sound better (i.e. less worse) on some fan makes compared to others, even if the specs look similar. But maybe not all manufacturers go that effort.

I can sympathise.

I recently purchased one of those Ikea Air Quality sensors. At first, I wondered why others had noted online about the fan noise, especially as the fan is tiny, but then sure enough I could hear it and once you do it drives you nuts. It must be the distinctive frequencies.... this is what that air quality sensor fan pushes out noise wise:

Anyhow, I did a quick search online to see if I could find some pictures and I found some on Amazon - this is a screencapture.

I'm guessing here, but maybe try and loosen that screw to see if it makes any difference as could be enclosure related (as @shabaz has noted).

For me noise that you describe can make me throw the unit out!

Are there any mechanical issues contributing to the noise? Move, wiggle and gig the fan housing to see if the noise changes. I have found thin, flat metal that air travels over can act like a reed in a wind instrument and add noise. Sometimes securing things down can lessen the noise level.

I could use a few quieter fans in my desktop computer. 

Noise could come from electrical fluctuations, bearing vibration or airflow modulation.

Electrical fluctuations get translated into acoustical noise by magnetostriction or electrostatic forces. You can test if this might be the cause by determining if the frequency of electrical fluctuations matches the frequency of the noise. The fixes to prevent these motions include firmer mounting or damping out the motions with rubber. It may be possible to filter the electrical signal a bit to minimize its effect.

Bearing vibration can sometimes be deduced by seeing if the fan rattles at all when shaken, or if there is any play in the impeller when it is wiggled.. The easiest fix is just to lubricate the bearings or bushings.

You can calculate potential airflow modulation frequencies by measuring the fan RPM and multiplying by the number of blades and obstructions. You can also get a little whistle effect if some flexible vane is flopping around in the airflow.

Any fixed noise frequency can be "amplified" by a resonant acoustic cavity. These can be altered or eliminated by stuffing something into them.

Does the pitch change with applied voltage or flow rate or orientation?

The frequency changes with the rpm of the fan, faster = higher, slower = lower, orientation and voltage aren't something I have access to measure at present.

BigG said:

but maybe try and loosen that screw to see if it makes any difference as could be enclosure related

I'm going to try the actual housing of the fan after other options, and when I have better lighting :) 

colporteur said:

Are there any mechanical issues contributing to the noise?

The fan and its enclosure are pretty solid from what it look and feels like. The sound doesn't change under pressure (eg, pressing on the fan, or its shroud or surroundings)

I would try lubricating the bushing simply because it is simpler than trying to guess what might cause an airflow whistle without being there.

dougw said:

I would try lubricating the bushing

I think this's going to be a factor. I appreciate the help, thank you :)

Here's a reveal of where the fan is situated:

It's inside of Valve's Steam Deck.

you can disregard the blue tape, that was there to check the noise while I moved the fan, here's what it covers:

The community behind the steam deck have discovered there's two brands of fan in the steam deck, this Delta, and one by Huaying, and the Huaying typically doesn't suffer from the high whine.

Securing the enclosure, and the nearby aluminium shielding has reduced the noise somewhat, but it is still there.

Before:


After: