Solving fan whine

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?

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.

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: