How to find total case airflow and noise

[hallam2003]

as general knowledge, i'd like to know how to find my case airflow (CFM) and total noise (dB) produced by my fans, HSfan etc. I can get a general guess on each fan, but i don't know how to figure it. I know there's a way, and it's easier thatn i think, i'm too tired to think right now..

Hallam

[nilknarf]

Put a CFM meter at the air intake and exhaust vents. Get a dB meter and make the room as quiet as possible other than the PC.

Tim

[hallam2003]

There's isn't a way to get a general idea from the given information from the fans?

Hallam

[Brangwen]

I think hallam2003 is right on the money: if you built the system or if you know what types of fans (brands/models) are blowing, vendors who advertise these items on the Web list the db and CFM of each.

Otherwise, Nilknark seems to have the right idea.

Brangwen http://www.sysopt.com/forum/wink.gif

[hallam2003]

ok, i know this information, but how to i add it all up, i mean i know approx. how mandy Db each fan produces, but i know i can't just add it all up, i mean...it has to overlapp right...if each fan is 30Db,an i have...say...10 of them..(i don't BTW)...it can't possibly be 300Db, they'd arrest you for that kind of noise...but i'm really looking foward to knowing how to figure the total air going through the case...I don't think i'm going to concided any exrta vents i have in the case, just what the fans bring in and out...


Hallam

[nunyadam]

The cfm of the fan alone will not tell you the airflow through the case . Unless you cut a hole the same relative diameter as the fan. those little holes most case's provide are very restrictive. of course a dremel will fix that.

nunya

[Axel]

Are you putting a system in an old folks home and worried about the noise and temp or what?

Why do you want to figure it out?

You could dive in real deep and figure BTU case load and the thermal transfer properties of the case materials, etc. etc.

Really quiet fans cost quite a bit more and eventually get noisy over time.....

The more fans you have pushing air into the case that aren't also sucking in dust and dog hair the better.... then don't obstruct the air flow in the case by blocking it with loose ribbon cables and tightly stacked drives..... then make sure you have a really good CPU fan and heat sink that has an extremely thin coat of good thermal paste between the sink and the processor.....

Then don't enclose your CPU in something like a tight desk space and expect good air flow.

If the noise is bothering you, build a secondary outer case with good air flow, but with acoustic foam on the inside - take the outer case off your PC and set it into this box.... Create a positive airflow into the outer box, but recess the fans deep into the box so the noise is buffered - and make sure you have unobstructed vents at the top of the box.....

Quiet as a mouse....

[This message has been edited by Axel (edited 04-27-2001).]

[krusty the klown]

...or go water cooling http://www.sysopt.com/forum/smile.gif

Good points made all round: a r8ed CFM for a fan is free air delivery - does not account for restrictions and a lot of noise is caused by turbulence - IOW having large restrictions placed very close to a fan.

Large slow revving fans will be quieter than small screamers @ the same CFM... but will cost more. Don't forget that you can run large fans @ 7V by connecting the 0V line to +5V, thereby keeping the noise down.

DeciBels is a logarithmic scale, so it's not quite as simple as just adding them up... a 100Watt speaker is only twice as loud as a 10Watt speaker on the DeciBel scale.