rushing noise from fan gratings?

[Timothy Daniels]

Part of the noise from the case fan in my PC seems to
be from the turbulence of air rushing past the fan's exit
grating (which is part of the case) - for the power supply fan
and for the case ventilation fan. This grating is stamped
out of the flat sheet metal that forms the chassis, not the
wire grating that is over the entrance to the fan on the
inside of the case. Has anyone cut this flat metal grating
away to see of it cut down the hissing noise of rushing
air? It occured to me that it might also improve ventilation
a little bit.


*TimDaniels*

 

[Will Dormann]

Part of the noise from the case fan in my PC seems to
be from the turbulence of air rushing past the fan's exit
grating (which is part of the case) - for the power supply fan
and for the case ventilation fan. This grating is stamped
out of the flat sheet metal that forms the chassis, not the
wire grating that is over the entrance to the fan on the
inside of the case. Has anyone cut this flat metal grating
away to see of it cut down the hissing noise of rushing
air? It occured to me that it might also improve ventilation
a little bit.

Yes, that's quite a common mod. Any time you have an obstruction near a
fan it will create noise. If we were talking about a propellor in
water, the term would be "cavitation". With air, I'm not so sure but
the idea is the same. My current PSU has a wire fan guard which
doesn't restrict air flow that much. I removed it anyway, just by
taking out 4 screws.

Ones that have stamped metal gratings should definately be removed if
you're concerned about noise. Tin snips should do it. De-burr with a
file or Dremel, but be extra careful about metal filings.

-WD

 

[spodosaurus]

Part of the noise from the case fan in my PC seems to
be from the turbulence of air rushing past the fan's exit
grating (which is part of the case) - for the power supply fan
and for the case ventilation fan. This grating is stamped
out of the flat sheet metal that forms the chassis, not the
wire grating that is over the entrance to the fan on the
inside of the case. Has anyone cut this flat metal grating
away to see of it cut down the hissing noise of rushing
air? It occured to me that it might also improve ventilation
a little bit.


*TimDaniels*

I also remove these when case modding. I then use adhesive to put a
rubber seal around the edge of the hole before mounting the thing wire
fan grille.

Ari

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[Timothy Daniels]

I also remove these when case modding. I then use adhesive
to put a rubber seal around the edge of the hole before
mounting the thing wire fan grille.

I've already taken off the wire grill on the inside of the fan.
I figured no wires would get close enough to interfere with the
fan blades, and it was too open to provide any degree of EMI
containment. The wider grating struts on the outside, though,
are both grounded and flat - perhaps providing greater EMI
containment and air turbulence. I'm leaning toward cutting
the suckers off and curling them back to provide a mount for
a cylindrical sound damping baffle. I notice my technical
reading is much easier without the sound of the PC in the
background.


*TimDaniels*

 

[Timothy Daniels]

Yes, that's quite a common mod. Any time you have an obstruction
near a fan it will create noise. If we were talking about a propellor in
water, the term would be "cavitation". With air, I'm not so sure but
the idea is the same.

In air, cavitation occurs, too, but it requires propeller blade tip
speeds in the transonic to supersonic speed regimes. This used
to happen with the P51 fighter planes of WWII, and the sound
of their takeoff was deafening. I heard one take off at Van Nuys
Airport (north of L.A.), and the sound stopped conversation all
over the airport for while.

My current PSU has a wire fan guard which doesn't restrict
air flow that much. I removed it anyway, just by taking out 4
screws.

Yup, took mine off, too.

Ones that have stamped metal gratings should definately be removed if
you're concerned about noise. Tin snips should do it. De-burr with a
file or Dremel, but be extra careful about metal filings.

Yeah, I hear metal filings on the motherboard is a show-stopper.


*TimDaniels*

 

[Ed Light]

I'm leaning toward cutting
the suckers off and curling them back to provide a mount for
a cylindrical sound damping baffle.

I tried that but never mounted it. I put acoustical foam on the inside of a
large pvc pipe with a small bend in it. When I held it over the fan outlet,
which was pretty loud back then before my Vantec Stealth fan went in, it
helped alot.


--
Ed Light

Smiley :-/
MS Smiley :-\


I notice my technical

 

[Timothy Daniels]

I tried that but never mounted it. I put acoustical foam
on the inside of a large pvc pipe with a small bend in it.
When I held it over the fan outlet, which was pretty loud
back then before my Vantec Stealth fan went in, it
helped alot.

That's approximately what I had in mind. I figured
I'd lead the air (and the sound) into a larger pipe or
box lined with self-adhesive carpet squares. I did
something similar at work with a workstation a
number of years ago, and the resulting quiet was
remarkable.


*TimDaniels*

 

[Overlord]

Yes, that's quite a common mod. Any time you have an obstruction near a
fan it will create noise. If we were talking about a propellor in
water, the term would be "cavitation". With air, I'm not so sure but
the idea is the same. My current PSU has a wire fan guard which
doesn't restrict air flow that much. I removed it anyway, just by
taking out 4 screws.

Ones that have stamped metal gratings should definately be removed if
you're concerned about noise. Tin snips should do it. De-burr with a
file or Dremel, but be extra careful about metal filings.

Drilled out mine with a hole saw. The center hole was dead center and
provided a great spot for the guide bit on the hole saw. Also, the
edge was very nice and not all that sharp and the wire guard I put
over the new hold had the outer wire circle dead over the cut edge.

-WD

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[Timothy Daniels]

Drilled out mine with a hole saw. The center hole was dead center and
provided a great spot for the guide bit on the hole saw. Also, the
edge was very nice and not all that sharp and the wire guard I put
over the new hold had the outer wire circle dead over the cut edge.

I just snipped the gratings off with an 8 in. electrician's wire cutter,
and the increase in air flow is quite noticeable. By holding the gratings
back in place by hand, one can feel the resistance that they imposed
on the air flow. But with the increase in case fan speed, there is a
low level "whirring" sound that is barely audible from in front of the PC.
It may be a product of unbalanced fan blades, worn bearings, and
the increased speed working together. Hmmm... another project on
my list: A muffler.


*TimDaniels*