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Effects of Grill Patterns on Fan Performance/Noise

Written on September 19, 2011 by Matt Bach


Fan grills are often underestimated in terms of their contribution to both fan noise and airflow. It would stand to reason that the more raw material present on the grill would cause a more restricted airflow, which in turn would cause a drop in airflow and a rise in noise. In our experience however, the shape and pattern of the grill can have a huge impact on noise due to the different types of turbulence that can be caused.

While the number of possible grill designs is essentially limitless, we will be testing some of the most common designs that come included with fans and chassis, as well as some popular after-market designs. A few of these grills can also found cut into window panels or stamped directly onto the metal body of a chassis itself by the manufacture.

The goal of this article is to determine exactly how much a grill design contributes to both the noise and airflow of a fan.

Test Grills

For our testing, we will be using six different patterns cut out of 3mm acrylic as well as three common metal grills that often come included with fans/chassis. The grill patterns for each are shown below:

Concentric Circles Grill Angled Slats Grill Honeycomb Grill
Concentric Circles. Simple design, used widely in the industry. Angled Slats. Often found on pre-installed fan mounts for acrylic chassis windows. Honeycomb. Very common on chassis where the grill is stamped directly onto the chassis frame.
Swirl Grill Loose Swirl Grill Turbine Acrylic Grill
Swirl. Found on some chassis fans, common on large household fans. Fragile due to the thin arms. Loose Swirl. Variation of the swirl with larger open spaces. Turbine. Uncommon, but shows up sometimes on budget chassis.
Metal Mesh Grill Metal Stamped Circle Grill Metal Wire Grill
Mesh. Very restrictive, often doubles as a loose filter. Stamped Circles. Variation of the concentric circles with the grill slightly raised above the fan Wire. Most common after-market grill with the grill slightly raised above the fan.


For all of our testing, we will be using an Antec 120mm Tri-Cool on both the low and high settings. This will give us both low and high airflow tests without the need to change the fan between tests.


We have found that the additional noise from grills is most prevalent on the intake side of the fan, so noise measurements will be taken in that configuration. The dBa meter was place at a 90 degree angle from the fan at a distance of two inches. This is much closer than dBa readings are normally taken at, but we expect the difference between some of these grills to be minimal so we wanted to make sure the changes were measurable. Because of this, our measurements will be in no way comparable to the manufacturer's specifications of noise.

Results are reported in both the raw dBa reading as well as a percentage over the reading of the fan with no grill.

*The ambient environment is 29 dBa

Low fan speed

Quietest No Grill 35.5 dBa  
Wire 36.0 dBa (1.4%)  
Mesh 36.0 dBa (1.4%)  
Swirl 36.0 dBa (1.4%)  
Loose Swirl 36.4 dBa (2.5%)  
Stamped Circles 38.0 dBa (7.1%) Difference in noise level starts to become noticeable
Honeycomb 38.0 dBa (7.1%) Grill starts to give a high-pitched "whining" noise
Concentric Circles 39.8 dBa (12.1%)  
Angled Slats 40.5 dBa (14.0%) Whining noise becomes very pronounced
Loudest Turbine 50.2 dBa (41.4%) Whining noise is more noticeable than the fan itself


High fan speed

Quietest No Grill 55.0 dBa  
Mesh 55.3 dBa (0.5%) Technically the quietest grill, but it raises the pitch of the fan noise making it more noticeable
Swirl 55.6 dBa (1.1%)  
Wire 55.8 dBa (1.5%)  
Loose Swirl 56.3 dBa (2.4%)  
Stamped Circles 57.8 dBa (5.1%) Whining noise starts to occur
Honeycomb 58.0 dBa (5.5%)  
Angled Slats 61.6 dBa (12%) Whining noise becomes very pronounced
Concentric Circles 62.0 dBa (12.7%)  
Loudest Turbine 71.0 dBa (29.1%) Whining noise is again more noticeable than the fan itself


From a noise standpoint, what exactly do these results mean? Basically, you should avoid concentric circle, slat, honeycomb and turbine style of grills if possible. The mesh, wire and swirl grills were all clearly the best performers in both the low and high airflow tests with dBa readings within 1% of each other. Likewise, the turbine grill is the loudest grill by a healthy margin; increasing dBa readings by 29.1-41.4%

The remaining question now is how much these grills are restricting the airflow of the fan. If the best grill in terms of noise is also is the most restrictive, it makes that grill much less desirable for use in a computer system.


Extech AN100To measure the changes in airflow, we used an anemometer (Extech AN100) with a custom adapter to adapt from our 120mm test fan to the smaller 80mm diameter of the anemometer sensor. The adapter is 200mm long, giving us a smooth, gradual slope from the 120mm side to the 80mm side. Using this type of adapter means that our CFM readings will be nowhere near the manufacturer's specifications, but should do a good job at giving us comparison readings. It will also be more real-world as a fan installed into a chassis is never going to perform at the manufacture rated open-air CFM levels.

We will again be testing with the fan on both low and high fan speeds, as well as testing with the grill on both the intake and exhaust sides of the fan. The results are listed below largely in order of best to least airflow. Due to some variances between the intake and exhaust results however, they are not 100% in order for each configuration.

Results are reported in both the raw CFM reading, as well as a percentage of the airflow based on the CFM reading of the fan without a grill.

*Results are in CFM Low fan speed High fan speed
  Intake side Exhaust side Intake side Exhaust side
No Grill 22.6 (100%) 22.6 (100%) 46.7 (100%) 46.7 (100%)
Wire 22.2 (98%) 21.7 (96%) 45.7 (98%) 45.2 (97%)
Stamped Circles 21.3 (94%) 22.0 (97%) 43.6 (93%) 45.0 (96%)
Swirl 21.5 (95%) 21.5 (95%) 44.3 (95%) 44.6 (96%)
Loose Swirl 20.75 (92%) 21.3 (94%) 43.2 (93%) 44.3 (95%)
Honeycomb 20.75 (92%) 20.6 (91%) 42.7 (91%) 42.7 (91%)
Concentric Circles 20.6 (91%) 21.1 (93%) 42.0 (90%) 43.4 (93%)
Mesh 20.2 (89%) 20.2 (89%) 43.0 (93%) 41.8 (89%)
Angled Slats 19.3 (85%) 20.2 (89%) 40.0 (86%) 41.3 (88%)
Turbine 19.5 (86%) 19.7 (87%) 39.7 (85%) 40.4 (87%)



The wire grill is easily the top choice in terms of both noise and performance. There are a few points where it was not the top result, but in those cases it was close enough that it was within our estimated margin of error.

The mesh grill, while being one of the quietest grills, is also one of the poorest in terms of airflow. Interestingly, this grill is the only one whose results deviated largely between the noise and performance sections. This is likely due to the fact that it is a much different style than the other grills we tested. Instead of having relatively large frames and openings, the mesh grill has a lot of smaller openings, but placed very close together. So while it is very restrictive, it does not create the same type of turbulence noise that the other low-performing grill designs such as the angled slats and turbine.

And lastly, the turbine grill is absolutely horrible; dropping airflow by ~15% and increasing fan noise by as much as 41% when the fan was on high.

Taking both noise and airflow into account, here is our final list of grill designs in order of best to worse:

  1. Wire
  2. Swirl
  3. Loose Swirl
  4. Stamped Circles
  5. Honeycomb
  6. Mesh
  7. Concentric Circles
  8. Angled Slats
  9. Turbine
Tags: Performance, Cooling, Fans, Chassis


Posted on 2011-10-04 22:34:35

I really like this test. I think about this some times, but, i don´t have the tools to make this.

Tank´s for this value information!!!

Posted on 2011-10-06 23:21:27

Thank you for this detailed, metric analysis.  I have thought about this issue but never had the time or energy to test it.  Well done!

Posted on 2011-11-01 00:03:59

Thank you for this thorough test. I've searched for an analysis on fan grills and this is the only one I've found. Keep up the great work!

Posted on 2012-07-06 01:45:16
Ramesh Babu3

Thanks for the details and through results shared.

Do you have any inputs on Grill design for EMI reduction?

Posted on 2013-01-17 10:49:06

EMI reduction isn't something I have very in-depth knowledge about, but from my (basic) understanding I would think that a fine metal mesh would work the best.

Posted on 2013-01-17 18:42:33

Very useful and practical data! EMI shielding is best for tighter patterns that are stamped into the sheet metal unless there is a functioning EMI gasket between the grill and chassis. By functioning, I mean that it makes good, continuous electrical contact with both the chassis and the grill. The chassis must be electrically conductive (no paint or oxidation). Otherwise, the long gaps between the screw holes will radiate, Grill patterns with similarly long openings will do little to shield EMI. As a product designer, I use wire grills when EMI containment is not a concern, and stamped honeycomb when it is. Stamped concentric circles appears to be a good compromise solution, providing better EMI shielding than wire, and more airflow than honeycomb with similar noise.

Posted on 2017-07-12 16:07:31

Great article. I was wondering why my new fans were so loud! I blame the honeycomb on my chassis. Had to lower fan speed to keep it bearable for watching videos.

Posted on 2014-01-06 22:04:37

Thanks for this. I noticed the higher pitch sound with my mesh covering my fans vs not covering. For me my fans seemed louder without any grill pattern and with other patterns vs having the mesh. Problem is because of the higher pitch the noise when using mesh is quite audible. Modding my case currently and not sure what I'm going to do

Posted on 2015-02-28 08:20:23
Jon Gardner

I'd like to see the results for a "modified concentric circle" pattern, where the "support" legs are curved like the swirl instead of straight from the center to the edge.

Posted on 2015-06-30 23:35:51

reason im here is about my 16" oscillating fans in my grow room. I don't care about safety or noise. Would it actually create more airflow with the metal guards off?

Posted on 2016-01-23 18:10:16

We were testing smaller fans, but the underlying principle should be exactly the same for larger fans like yours. So yes, you should see slightly better airflow with the metal guards removed. How much depends on how restrictive those guards are. If they are just the standard wire grill, It will probably only be a few percent better airflow. Still, if you don't care about safety then you might as well (those fans can have a lot of power, though, so it will definitely be much more dangerous that way)

Posted on 2016-01-25 20:03:58

but the mesh also protects against dust right?

Posted on 2017-02-04 06:37:19

*ravages case with tin snips* =O looks like crap, but oh so much quieter. Im not sure why cases dont come with holes and wire guards anymore.

Posted on 2017-02-12 16:05:04

I think im in the same boat. During testing my fans were damn quite, installed them properly and now the buzzing is insane!(these are vary high performance fans! noctua industrial version)

Posted on 2017-07-18 22:34:00

Very useful data, thanks!

Posted on 2017-02-13 22:07:55
มูฮัมหมัด ซุลไคโรล

could provide static pressure. some say swirl grill provide more static pressure

Posted on 2017-05-28 04:57:26

That sounds like absolute crap. there shouldnt be any reason for that to be the case so i wouldnt believe it unless someone reliable tests it.

Posted on 2017-07-18 22:33:04

I like the 100% performance results the best

Posted on 2017-09-03 21:13:13
Mihail Golu

Thank you for the information! Do you know a relation between nominal airflow of the fan and number and dimension of holes needed (total holes surface of the Grill)? I wanted to know how much will increase the noise level this relation. Is some how a rule?

Posted on 2018-10-15 09:00:15
Bhezret, 66 let, Kohoutovice


Posted on 2019-04-20 19:12:01

Just removed my exhaust fan grille which I think meant more for safety. Couldn't notice less noise but at least now it seemed to be a better vent hole when it's turned off.

Posted on 2019-08-17 01:46:12
Daniel Zegonz

How did you remove the grill? I'm considering dremmeling it out.

Posted on 2020-02-01 04:57:50
Jesus Moreno

Thank you for this test, I don't think is necessary to have a grill at the back of a pc case. Please manufacrurers, include a Wire grill and we choose is use it or not. I won't use it. I have a case with honeycomb grill and the increase in noise is noticeable, also the airflow decreased by quite a bit. I think that more than 25%, probably due to the low static pressure fan design.

Posted on 2020-01-24 13:00:33

In my Phanteks Evolv ITX I added a rear 140mm NF-A14 PWM fan as Intake (for extra airflow and also more positive pressure inside the case), and basically this fan at 750 rpm is the most annoying (in terms of noise) thing in my PC.
In other words. I can stand the other 4 fans running at 900-1100 RPM on load. But I can't stand this 5th rear fan running even at 750 rpm on idle. The noise is so acute that I can listen it even if the ambient is noisy.

I'll try putting a dust filter (because is something I need anyway as it is a rear intake now), if it doesn't work, I'll cut down the grill with my (new) dremel tool.

In the past I used the same fan as exhaust in the same honeycomb back grill without major issues. So I guess my issue is only when the fan is pulling air from the grill.

Anyway, thanks a lot for the article.

Posted on 2021-01-31 21:25:17
Daniel Arnold

Why not simply remove the front grill? I've done this with several fans including a Vornado 630 and Vornado V-fan. Both are quieter and produce greater airflow without the grill, especially the 630 with its swirl pattern grill. I've tested both for safety simply by putting my hand to the running fan blades. The blades do not have enough force to cause discomfort, let alone injury.

Posted on 2021-07-03 01:58:33