Does more fans means more noise?

[supertle55]

This may sound like a silly question, but I am not sure. My system right now is incredibly noisy and I have about 8 fans altogether. Is the noise I am hearing an accummulation of all the fans together or is it the loudest fan I have ? I have the scythe ultra kaza which is the loudest at 46 dBA. All my other fans are around 20-30 dbA.

fyi - I have the Cosmos 1000 case. Its so noisy that I can hear my case humming through the floors from my bedroom to my kitchen. I am thinking of getting rid of the scythe and a few fans. Heat may be a problem, but the noise is now getting to me.

 

[JaYp146]

You are hearing the accumulation of the fans.

Best way to quiet things down is to get lower RPM fans (SFlex 1900 RPM instead of Ultra Kaze?), make sure they're soft mounted (rubber grommets), and keeping the case on a soft surface (foam) wouldn't hurt either.

What are the "other fans" ?

 

[wkwong11]

Yes, more fans is more noise. However, if you want to quiet your case, you'll want to start with the loudest fans first as they'll make the biggest difference. I suggest getting a few of these Cooler Master fans as they are pretty cheap and very quiet: http://www.svc.com/200007680.html

For case fans, you probably don't need all that much airflow. You can opt to go with 1 or 2 higher CFM fans for your CPU cooler.

Check to see if you have any chipset or VGA coolers that have loud fans as well. You'd be surprised how much noise those small fans make. They often need to spin at very high RPM's to produce any kind of meaningful cooling and thus produces very annoying noises.

A simple test is to put your finger on the fan hub to slow it down until it stops (or just unplug that fan) and you can hear the overall difference in noise that exact fan is making.

 

[Zepper]

The calculation isn't linear, but each extra fan does add some noise. The quality of the noise is often more important than the absolute level. You know how some types of sounds irritate the heck out of you even at relatively low volumes, while others are quite tolerable even when pretty loud.

.bh.

 

[TheVrolok]

Originally posted by: wkwong11
Check to see if you have any chipset or VGA coolers that have loud fans as well. You'd be surprised how much noise those small fans make. They often need to spin at very high RPM's to produce any kind of meaningful cooling and thus produces very annoying noises.

A simple test is to put your finger on the fan hub to slow it down until it stops (or just unplug that fan) and you can hear the overall difference in noise that exact fan is making.

This is the truth... the two loudest fans in my system are, by far my NB fan, and my GPU fan at 100% (now replaced by water). I decided not to go with a NB waterblock for this system as I'll most likely upgrade the board in a few months but man.. part of me is wishing I did.

 

[supertle55]

Thank you for all the replies. Here's my system setup from a previous thread I made

http://www.imgx.org/pfiles/701...ir%20Flow%20Design.JPG

http://www.imgx.org/pfiles/7020/othersideopen.jpg

original thread at, http://www.erodov.com/forums/c...00-fan-setup/6855.html ,

I copy this guy's idea with the exception of having a fan in the HD Drive Bay.

My system was running pretty warm with the I7 920 overclocked to 3.8ghz. I also have my ATI 4890 OC as well. When the case door was opened, temperature dropped a good 5-10°C.

My cooling setup:
Noctua NH-U12P SE1366 120mm SSO CPU Cooler, replaced the fan with the rocket engine 3000 RPM Scythe Kama Kaza blowing 133 CFM for $10

The Noctua fan that came with the cool was placed standing up position labeled F1

Bgears b-ice Blue 120mm Blue LED Case Fan, this one replaced the stock fan on the rear panel, 58.3 ±10% CFM

I am running now about 40°C idle on my CPU. I'm under 60°C under gaming load which is around 37% cpu usage. My ATI 4890 is about 59°C idle.

My room temp is usually around 72° F. I thought I share this information to all cosmos 1000 owners that this case DOES get very WARM if you do not add additional fans in when you are overclocking.

Actual photo of my system:
http://farm3.static.flickr.com...03394_ec87e42125_b.jpg

http://farm4.static.flickr.com...03704_328b8b1a3f_b.jpg
Yes that's the crazy scythe kaza blowing 133 CFM at 46 dBA

 

[vj8usa]

Originally posted by: supertle55
http://farm4.static.flickr.com...03704_328b8b1a3f_b.jpg
Yes that's the crazy scythe kaza blowing 133 CFM at 46 dBA

Maybe this is a dumb question, but why are both your CPU fans blowing into the heatsink, pointing at each other? Wouldn't you get much better airflow if they were both moving air in the same direction?

 

[wkwong11]

Originally posted by: vj8usa

Originally posted by: supertle55
http://farm4.static.flickr.com...03704_328b8b1a3f_b.jpg
Yes that's the crazy scythe kaza blowing 133 CFM at 46 dBA

Maybe this is a dumb question, but why are both your CPU fans blowing into the heatsink, pointing at each other? Wouldn't you get much better airflow if they were both moving air in the same direction?

Good eyes! Those fans ARE both blowing into the heatsink and that is NOT good. You are causing air to be trapped inside of the heatsink, causing excessive pressure and turbulence. I would turn that fan around right away. You should get some considerably lower temps, especially on load.

 

[supertle55]

Originally posted by: wkwong11

Originally posted by: vj8usa

Originally posted by: supertle55
http://farm4.static.flickr.com...03704_328b8b1a3f_b.jpg
Yes that's the crazy scythe kaza blowing 133 CFM at 46 dBA

Maybe this is a dumb question, but why are both your CPU fans blowing into the heatsink, pointing at each other? Wouldn't you get much better airflow if they were both moving air in the same direction?

Good eyes! Those fans ARE both blowing into the heatsink and that is NOT good. You are causing air to be trapped inside of the heatsink, causing excessive pressure and turbulence. I would turn that fan around right away. You should get some considerably lower temps, especially on load.

Great catch!! I never noticed those arrows on the fan before. I was always wondering how you can tell the direction of the airflow on a fan. My way was always spinning it with my finger and feeling the flow. I guess that did not work! No wonder my noctua was sucking so much with its original fan.

 

[supertle55]

Update - After removing the fan pointing at the wrong direction of the heatsink AND removing the crazy loud Scythe Kaza (replacing it with the original Noctua fan). My CPU temperature remained the same which is great! I also removed the fan sitting on top of the HD Bay.

The Scythe Kaza though loud and with another fan pointing against it created good overall circulation around the area. BUT now my video card ATI 4890 is running 80° C while playing Crysis at stock default settings after removing the Scythe Kaza. I don't recall it being this high before. So now I have to manually crank up the ATI fan speed and that is creating a loud buzz to keep the GPU temperature in the lower 70s. So I am sort of back to where I am. Trying to find a balance and setting the ATI 4890 at 35% fan speed for now but temperature still creeps up after running Crysis for a while.

 

[Zepper]

Vid card fans are often the loudest in a given system. Get something like a Zalman bracket and aim a relatively quiet fan in the direction of your vid card so you can crank the vid card fan back.

.bh.

 

[imported_Scoop]

80C GPU is nothing to worry about, when it's creeping up to 100C, that's when you might want to do something about it. Otherwise, as slow as you can. More fans doesn't mean more noise if you have a noise source that is clearly louder than anything else. Like that Scythe Ultra Kaze.

 

[Operandi]

dBA goes up by 3 every time you double the source. 2 fans rated at 30dBA would be 33dBA, 4 would be 36 for example.

What is often more important is the tone of the noise, smaller high RPM fans will be perceived as being louder and more offensive than larger slow RPM fans even if their dBA rating is the same.

 

[Eureka]

Originally posted by: Operandi
dBA goes up by 3 every time you double the source. 2 fans rated at 30dBA would be 33dBA, 4 would be 36 for example.

What is often more important is the tone of the noise, smaller high RPM fans will be perceived as being louder and more offensive than larger slow RPM fans even if their dBA rating is the same.

A simpler way to state it is, +3dB = 2x. So 3dB = twice the noise.

However, you're also assuming that two fans is exactly double the noise of one fan. I'm not sure how well that translates into real world application.

Originally posted by: supertle55
Great catch!! I never noticed those arrows on the fan before. I was always wondering how you can tell the direction of the airflow on a fan. My way was always spinning it with my finger and feeling the flow. I guess that did not work! No wonder my noctua was sucking so much with its original fan.

The easiest way to tell fan direction is to look at the blades. The side that is concave (curved inwards) is the side that air is coming out of. The side that is convex is the (curved outwards) is the side that feeds the fan. Basically, the concave side is the direction of the airflow.

If you need an example, look at any table fan.

 

[Zap]

Originally posted by: Eureka
The easiest way to tell fan direction is to look at the blades.

I thought the easiest way was to look at the arrows molded onto the sides?

 

[imported_Scoop]

Originally posted by: Zap

Originally posted by: Eureka
The easiest way to tell fan direction is to look at the blades.

I thought the easiest way was to look at the arrows molded onto the sides?

I thought the easiest way was to look at which side the sticker is on the hub

 

[Operandi]

Originally posted by: Eureka
A simpler way to state it is, +3dB = 2x. So 3dB = twice the noise.

However, you're also assuming that two fans is exactly double the noise of one fan. I'm not sure how well that translates into real world application.

I don't know how thats simpler but it's wrong, 3dBA is not twice the noise. Twice the noise would be 20dBA to 40dBA.

If you have two 120mm fans rated at 23 dBA you will end up with 26 dBA total. 1 dBA is the lowest unit of sound the human ear an detect, so +- 3dBA is pretty insignificant.

 

[Eureka]

Originally posted by: Zap

Originally posted by: Eureka
The easiest way to tell fan direction is to look at the blades.

I thought the easiest way was to look at the arrows molded onto the sides?

Not all fans will have arrows. Sticker's a pretty good idea, too.

Originally posted by: Operandi

Originally posted by: Eureka
A simpler way to state it is, +3dB = 2x. So 3dB = twice the noise.

However, you're also assuming that two fans is exactly double the noise of one fan. I'm not sure how well that translates into real world application.

I don't know how thats simpler but it's wrong, 3dBA is not twice the noise. Twice the noise would be 20dBA to 40dBA.

If you have two 120mm fans rated at 23 dBA you will end up with 26 dBA total. 1 dBA is the lowest unit of sound the human ear an detect, so +- 3dBA is pretty insignificant.

Decibel is not a linear scale, its a logarithmic scale. Here's a nice description:
http://www.endpcnoise.com/cgi-bin/e/decibels.html

The measurement of noise (bels and decibels) is logarithmic. In other words 40 decibels is not just twice as loud as 20 decibels. And, 40 decibels is actually about nine times as loud as 20 decibels.

+3dB is a very significant increase.

Another nice link:
http://www.howstuffworks.com/question124.htm

If you notice, a jet engine is 120dB while a conversation is at 60dB. A jet engine is not twice as loud as the human voice.

 

[Operandi]

Originally posted by: Eureka
Decibel is not a linear scale, its a logarithmic scale. Here's a nice description:
http://www.endpcnoise.com/cgi-bin/e/decibels.html

The measurement of noise (bels and decibels) is logarithmic. In other words 40 decibels is not just twice as loud as 20 decibels. And, 40 decibels is actually about nine times as loud as 20 decibels.

+3dB is a very significant increase.

Another nice link:
http://www.howstuffworks.com/question124.htm

If you notice, a jet engine is 120dB while a conversation is at 60dB. A jet engine is not twice as loud as the human voice.

Since it's not linear using terms like twice as loud tend to be confusing.

In terms of 20dBA or 23dBA of fan noise 3dBA is pretty insignificant since most things going on around the computer will be louder anyway. 100 dBA vs. 103 dBA is more significant.

 

[Eureka]

Actually, that's one of the very advantages of using decibels. +10 decibels = 10x as much. +20 decibels = 100x as much, and so on. It's quite the same as using scientific notation. And you can't ever say 3dB is every insignificant, if you're in a dead quiet room, you're going to notice the difference in 3dB (which matters with HTPCs).

 

[Operandi]

Originally posted by: Eureka
Actually, that's one of the very advantages of using decibels. +10 decibels = 10x as much. +20 decibels = 100x as much, and so on. It's quite the same as using scientific notation. And you can't ever say 3dB is every insignificant, if you're in a dead quiet room, you're going to notice the difference in 3dB (which matters with HTPCs).

Your right it can be. It all depends on the noise floor.

The point I was trying to get to was dBA's don't add up like many people think they do. And you don't have to worry about the noise two 23 dBA case fans create if your CPU HS/F is making 36 dBA.

 

[terentenet]

In theory, 2 sound sources that are at equal distance to the listener, will double the sound level. In real life, things work differently. My computer has 21 Noctua NF-P12 1300 fans, all spinning at 1300rpm. A Noctua NF-P12 1300 when at full speed produces 19db. When the system is on, I cannot hear the fans, but rather the sound of the air circulating. I have a bunch of Ultra Kaze 3000 around (wanted to use them at some point). I'm telling you, If I start one of those UK 3000 fans, you will not be able to hear my system if the system is 2 feet away and the Kaze 5 feet away. I don't have any means to measure the sound level... this is just my ear making the comparisons. The Kaze is rated at 45db.
The 21 fans start at 19db.
1 fan = 19db
2 fans = 22db
4 fans = 25db
8 fans = 28db
16fans = 31db
so.... 21 fans would be about 32db... The fans themselves produce 32db, but the air moving through the radiators (and it's allot of air) produce about 40db (not loud, but you can hear it).