How are Fan insulators? The silicon gel kind..

[simms]

Right now my NB and my GPU are passively cooled, the CPU has a 20dB 92mm and the PSU and out take has 21dB 80mm's.

So, can I make it quieter without doing volt mods? How are these insulators? Buy or no good?
http://mirror.memoryexpress.net/ProductDetail.php?DisplayProductID=3595
It's $7 for 2.

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Is there really a difference in noise having a OEM case grill compared to cutting it out and putting another grill 2mm away from the fan?

Simon

 

[nellienelson]

by removing the grill that will stop the air from being disturbed by the grill (vocabulary has deserted me) and so the turbulence (ah it returns) that would be caused by the grill, and so create the noise will not exist. thus the reduction in dB. think thats correct.

 

[Jeff7181]

Having the air blow over something like that creates "wind noise." For a more exaggerated demonstration, stick your hand out the window of a car... you'll definately hear the wind whipping around and through your fingers... same thing happens with fan grilles but on a smaller scale of course. People with ultra quiet PC's like to remove those flat faced grilles and replace them with a wire one that's more aerodynamic and therefore doesn't produce as much wind noise by disturbing the airflow.

 

[Aftermath]

I think it's more of a problem with grills that are much more "busy" than that. Something like this. The air has to move through those holes, which cause a lot of turbulance, thereby creating more noise. So cutting it out and using a grill that reduces the amount of air turbulance should lower the amount of noise created.

But as far as the process, yeah, just cut around the circle like you drew to remove the current grill, then screw in the new one. With a good dremel, it's a pretty painless process. I would sugguest being extremely cautious though. Make sure to take everything out of your case before cutting and modding. A few metal shavings could wreak a lot of havoc.

 

[usernamemax20charact]

To really cut down on wind noise, wouldn't it be even better to just remove the grill and not put one back on?

 

[Auric]

Removing grill increases airflow and lowers noise caused by turbulence. Adding back another like those in link 3 will return noise yet fail to guard so are just silly cosmetic items. Wok the heck is "shinny steel" anyway? :roll:

 

[Jeff7181]

Originally posted by: usernamemax20charact
To really cut down on wind noise, wouldn't it be even better to just remove the grill and not put one back on?

Not if you have animals or small kids who might be interested by a hole in the computer =)

 

[JBT]

I like to cut the holes out and use the regular .99 cent grills from SVC ect. Reduces noise and increases air flow = WIN WIN situation.

 

[Navid]

Originally posted by: simms
The back of my case looks like this roughly: http://www.slcentral.com/ahanix-dbox-silver-pc-case/back.jpg

Do they mean cut out cut out the grille like this? http://www.simon-leung.com/img/back.jpg

And do I replace it with this? http://www.genitechcomputers.com/products/description/80mm+Laser-Cut+Fan+Gril+-+Atomic/index.html

Will this lower dB? I don't understand how removing metal that is 1mm away from a fan and replacing it with metal 2 mm away from a fan will reduce much noise.

Noise from a fan can be categorized in two completely different types. One is the noise from the motor. It is the friction of the rotor with the comutator that creates that noise. The other noise is caused by the movement of the air that is moved by the fan blades. This second noise can increase if there is an obtruction in the way that could disturb the air flow. The friction of air to the obstructing object would create additional noise. Removing the grill alltogether would minimize this noise. But, it is not recommended if children are going to through candy inside the box, or worse put their hand in!
Removing the grill maximizes air flow also, which is the whole purpose of the fan to begin with.

 

[simms]

Right, but the thing is, is there really a difference in having the OEM grille there, and removing that grille and replacing it with one that is just like 2mm farther from the fan?

And edit for new equestion.

 

[Mik3y]

with the decibels added up, it should be around 30-40db.

 

[Navid]

It is more the shape of the grill than its distance from the fan. An aerodynamic object has less friction with air than a flat object that is held perpendicular to the flow direction. A grill made up of round wires is more aerodynamic than a flat layer of metal with holes in it.

If you have two things that add up in amplitude, they add up this way.
If each of them was 10dB, the total result would be 16dB.
This is because dB is a log scale. So, doubling something's amplitude is the same as adding 6dB to it.

But, if the two things you are adding are not co-related, like the sound from two fans that are not identical, they will add up in power, not in amplitude. Then, they add up this way.
If each of them was 10dB, the total result would be 13dB. Doubling power is like adding 3dB.

 

[Navid]

If you have 3 fans that are 20dBa each and are all the same distance from your ears and we assume that the noise adds up in power and not in amplitude since they are not co-related, the overal sound will be 24.7dBa.

Your situation is much more complicated than this. The fans are not at the same distance from you. There are blockers in the way of some of them, not all. They have different frequencies. Each person's hearing is different and have sensitivities to different frequencies.

It is not simple to just come up with a number.

 

[simms]

Navid, thanks for your responses. Thing is, will it make much of a difference? I'm not too sure I can notice a 0.001dB difference between 3x20dB fans, and 2x20dB and 1x21dB.

How does the math work? Have a link?

Simon

 

[Navid]

To find dB for something, you find the Logaritm of that number and multiply it by 20 if we are talking about amplitude. So 10 Volts is 20dBV.

Now if you add 10 Volts and 10 Vols, you have 20 Volts. If you find the Logaritm of 20, it is 1.30102.....
That multiplied by 20 to come up with dB is 26dB.
So, doubling something is like adding 6dB.

Things are different if we talk about power.
Sorry, I don't want to bore you. let me just say that if you double power, it is like adding 3dB.

 

[Navid]

Originally posted by: simms
Navid, thanks for your responses. Thing is, will it make much of a difference? I'm not too sure I can notice a 0.001dB difference between 3x20dB fans, and 2x20dB and 1x21dB.

How does the math work? Have a link?

Simon

These are some links.

http://www.sizes.com/units/decibel.htm
http://www.wordiq.com/definition/Decibel
http://www.schoolscience.co.uk/content/4/physics/corus/sound/psch1pg3.html
http://www.screensound.gov.au/glossary.nsf/Pages/Decibel?OpenDocument

 

[simms]

No no, it's interesting. I'm trying to understand. Where did the volts come into play?

I get your middle paragraph. What if we were to triple something? 20*log20 gives us 2 fans.. and for 3?

I doubt I can hear the difference between 26 and 27 dB right? I guess the main point is to have minimal fans running in your case.

 

[Navid]

The best thing to do, is to identify which fan it is that you are hearing. You can do that by opening the case and carefully stoping each fan by pressing on the middle of the blade, where there is minimum movement only momentarily of course. Listen for the noise change as you stop a fan. Eventually, you can identify the offending fan.

Then, you can decide how to reduce the noise of that fan. Change it with a quieter one, reduce its RPM, replace the heatsink with one that has a better efficiency so that lower RPM fan be sufficient.

Then, after quieting down the loudest fan, another one of the fans becomes the loudest one. You can do the same thing about that one.

At some point, you have to stop. This can go on forever!

 

[sunase]

It's funny, but I've found the cheap OEM grills often *decrease* the noise of the fan. Compared to the wire grills the OEM slot or to a lesser extent holed grills block a lot more of the opening and thus motor sound as well. I think people who care about fan noise are a touch mental, though, so all my fans are standard at standard rpm - meaning the motor noise is the primary component of the overall fan noise. I suppose if you had a quiet fan things might be different. Now I know people are going to whine that such grills block air flow as well, but so would a sound baffle to some degree and it's obvious you don't care about real cooling if you care about noise anyway. ;p