Performance Vs Noise - Experimentation
 

Original Thread:http://www.extremeprometeia.com/foru...3234#post33234

Okay, got that out of the way - that juat about explains why this thread is here :)

I have the following test equipment - I know it's not near the best but it will provide myself and others with a way to compare different manufacturers fans.

DAWE Sound Level Meter (797900)
Tenma (726638) Anemometer

Fans (so far collected):

AeroCool Turbine 1000 Fan
Cooler Master A12025-12CB-4KN-L1 PL12S12L
A.C. Ryan 12CM UV fan
SilenX IXTREMA IXP-74-14
Akasa Model: DFB122512L
Akasa AK-183-L2B Orange
AcoustiFan 120 AF120C
NMB Model: 4710KL-04W-B10
PANAFLO Model: FBA12G12H
PANAFLO Model: FBA12G12M
Themaltake Thunderblade Model: TT-1225

That's it for now. But will continue to add more :)

The current proposed test methodology will be:

Fans measured in free air
The fan will be measured 1 Meter away, horizontal to the dB sensor.
I have an mCUBE digital which I believe uses PWM to power the fans, however not all the fans respond well to it - the Ryan goes nutty.
So using both methods to power the fans would be a good idea, especially with PWM becoming more and more popular.

More details can be found on the original thread at EP-UK.

Please advise, constructive criticism welcomed - I want this to be a useful resource for others :)

Re: Performance Vs Noise - Experimentation
 

C'mon folks this is spose to be a useful resource for everyone. Marci pointed me here as you guys are meant to be the more intelligent cooling poeple :D

Upgraded the CFM meter to:

CFM MAster - DCFM8901

Re: Performance Vs Noise - Experimentation
 

Why don't you start by listing exactly what you want to test on these fans?

-Noise
-actual airflow

Does that sum it up?

For noise, ideally you'd have a soundproof room (or enclosure), and a sound recorder for which you know the characteristics, throughout the human sound spectrum.

For airflow, you need a fan testing chamber.

U need links?

Re: Performance Vs Noise - Experimentation
 

sounds like a good experiment to me.

Get marci to send you a pa.120 too ;) and see if you can get hold of a heatercore, and one (or both) of the black ice series to test pressure resistance vs noise - that would be especially useful here.

Re: Performance Vs Noise - Experimentation
 

Note that a thermal anemometer reads the air velocity over the sensor, how do you intend converting that (local) velocity to CFM through the fan ?

what is the mic floor (lowest level) ?

Re: Performance Vs Noise - Experimentation
 

I woudl of thought a thermal anemometer woud convert all that stuff internaly either that or there is an ASME, ISO etc spec on it.

Re: Performance Vs Noise - Experimentation
 

While I’m here, and sorry if this sounds like random facts. I type like a robot apparently.

You’re going to want to measure back pressure and its effect on noise there is also some effects of near fan geometry causing excess noise. This is noted very handily in the BTX spec, basically the dominant sound frequency you should get out is caused by the fan blades interacting with the supports. This is why artic silencers suspended fans are so good as the fan supports are so far away even though having no shrouds makes them awfully inefficient as fans. To create a back pressure maybe a long duct with an orifice plate (a plate with a circular hole) this should create a back pressure to work with. Measuring without a back pressure is pretty much pointless as all fans are subjected to one. There is an effect as well of air recirculation back around to the entrance from the exit. If the fan is completely free and some back pressure being caused by momentum conservation if it’s hanging from springs (the suspended springs move as the fan creates a force trying to balance the momentum of the air out, so it deflects to balance everything out).

One thing to remember about thermal anemometers is they like a nice uni-directional flow so it might be better to put some lamina flow guides in. This may be nothing more than a box grid made out of paper but it should help. I’ve never used the things 9themral anemometers) myself though, so you may get away with it.

On the sound pressure meter make sure to measure when there is less noise about. If your in a built up area this means staying up late or getting up early. And keep the measurement point and microphone direction as this will help make sure the measurement is a constant.

Re: Performance Vs Noise - Experimentation
 

ah, 'free flow' ?
speed bumps ahead

Re: Performance Vs Noise - Experimentation
 

A friend of mine was doing some self-made airtunnel testing for some sporting equipment - he used a bunch (probably nearing or exceeding 1000) of straws glued together to make a honeycomb arrangement. Too much pressure drop for this situation, i think - but it was an interesting solution.

Re: Performance Vs Noise - Experimentation
 

I was thinking more cross hatch from a ice cube tray (preferably for making small ice cubes). I swear ive seen a plastic grid around somewhere, in something common that would be useful. Could try acetate slides for overhead projectors.

Re: Performance Vs Noise - Experimentation
 

thats the correct soln but does have a dP, lengths and dias speced (for turbine air mtrs ?) of x tubes inside a tube
none of this is possible as he wishes to test eh ?

Re: Performance Vs Noise - Experimentation
 

Testing free air tells you next to nothing, fans can change 10 dBA as you go up the res. curve.

Standard practice usually involves an INCE Plennum or "Mahling Box" (george Mahling IBM) Bacically a box frame covered by a mylar flim with a sliding gate at the rear with a pressure tap on the inlet side.

Allows you to test the fans across the /flow/pressure curve

If you request flow data most manufacturers will provide it. then all you have to do is match the pressure point.

probably only cost 100-$200 to make.

You have to watch at the 1 m that you do not get noise canceling bounce, mic/source location is important

Re: Performance Vs Noise - Experimentation
 

That is what I was looking for! :)

I would like to disagree that measuring the fans in free air indicates 'nothing'. It gives people (myself) some kind of comparative figures which are much better than comparing all those different manufacturers figures!

I do however understand it is not ideal; but better than nothing. I would like one of those fancy boxes mentioned, but am strapped for cash. Adding another variable to the situation would also complicate the results - although good for some ;)

I was thinking about strapping the fans to my CM Stacker as a test frame for another set of dB results - however, this rig would change over time :(

If anyone has an idea or suggestions for a basic resistance setup that could be easily implemented I'm open. I was thinking of attaching a sheet of Bounty over the intake?!

Cheers for all the advice so far folks :)

Re: Performance Vs Noise - Experimentation
 

It has also been suggested that a fan filter (or one on each side) would do the job. Another suggestion was to stick the fan to the centre of a rad in pull config...

(I have a PA120.3 I could do this with)

Re: Performance Vs Noise - Experimentation
 

look into 'free air', you do not understand the experimental issues

Re: Performance Vs Noise - Experimentation
 

Air Flow Vs. Pressure Characteristics
Parallel & Series Operation
Stall of Axial Flow Fans

Basic Fan Laws
How to measure Airflow vs Pressure
How to Achieve Low Noise
Accoustic Noise
EMI
Introduction: Forced Convection Cooling
How to select the right fan or blower


Measuring Airflow Resistance
actually not a very complicated test device, oh except the part where there are the calibrated nozzels, those defy DIY even if you can machine them yourself, and the part where you have to adjust your findings based on the relative humidity and barometric pressure thats fun Im sure :p

Re: Performance Vs Noise - Experimentation
 

that would be exactly what you are comparing more often than not
only without the anechoic room

http://www.sunon.com.tw/english/wealth/tech/tech-07.htm

as mentioned of limited realworld value

of course some are better than others

http://www.comairrotron.com/engineering_notes_03.asp

and to further belabor and summarize the point Mike Chin of SPCR

University of British Columbia Fan Noise & Airflow Research Project @ SPCR

Re: Performance Vs Noise - Experimentation
 

"This means that the manufacturers' specifications are often not directly comparable. It takes a careful, trained engineer to calculate specifications obtained from disparate techniques into comparable numbers. Even for them, it might actually be easier and certainly more accurate to take prospective fan samples and re-measure with one consistent technique."

which is the conclusion I came to after comparing the actual fan preformance when connected to a sink or rad
fan performance is so unique that fitting a specific fan to a sink by test will yield improved performance over that having the 'best specs'

Re: Performance Vs Noise - Experimentation
 

and gets even more complicated once the fan combined with the component is actually placed in its environemnt with other components

http://www.comairrotron.com/engineering_notes_03.asp

not to discourage you in your pursuit, but rather to make you aware of some of the variables involved so that you inturn can pass on the caveates to your adopted test proceedure in an easily understandable way to your readers
along with some tips about how they can get the most from thier choice (read the whole link) and factors that will influence the sound signiture even after its been installed (temperature gradient, dust level ect) ;)

Re: Performance Vs Noise - Experimentation
 

lets have a shift here as this is my intended audience

1) when a fan is mounted with a shroud it is possible to get a plenum pressure indicating roughly where that specific match-up falls on that fan's PQ curve (w/unconfined/unconstrained discharge)
- anyone have an 'experimental' feel as to how shallow the shroud might be before the pressure was non-uniform (otherwise assumed)
- pitot tube considerations ? (airspeed too low to matter ?)

2) if it is accepted that the fan inlet air temp is reasonably characterized by TC msmt in each quadrant over the fan mid-blade (the Intel procedure), would the same be true for the fan/rad discharge ?
- with some other factoids could calc mass/vol air flow ?

Re: Performance Vs Noise - Experimentation
 

In an effort not to make this to much of a downer.

If the fan is shrouded (by a relatively non confining shroud) and is placed far way from the source of resistance and the other side is free air then it’s fairly independent of the surroundings (except of course back pressure). This should PARTLY remove the effects of close rad distance that bill was talking about. To be more correct the fan should be 10 diameters from the exit and exit into a smooth duct expanding out from the fan at greater than 15 degrees to a large (d x 2 say) radius but I wouldn’t worry too much about that.

For sound levels just use dBA and add a few of your own thoughts. dBA is industry standard.

Re: Performance Vs Noise - Experimentation
 

no bobo, you need to do some of this
the 10 dias have friction, how is this addressed ?
better to replicate the use conditions for 'real' results

I can run a traverse and measure the variation too, better than guessing I suppose

what do you think of the heat balance notion ? too loose ?

Re: Performance Vs Noise - Experimentation
 

I'd like to see a frequency graph along with straight dBA levels, personally. Much more useful to see the characteristics of the fan noise, rather than just the straight noiselevel.

Re: Performance Vs Noise - Experimentation
 

I think you have to keep in mind that absolute values will not be realized in your testing.

Lacking a anechoic chamber, outside interference will affect any measurement you take. While doing some fan development I was forced to go to work at 2 am in the morning. Idling trucks a block away, air conditioners on adjacent buildings, refrigerators, flourescent lights, your breathing.....will affect the result. Additionally reflective surfaces can be a real problem.

even if you get your background down to 30dBA it will still add several dBA to your result- 38 dba can end up being 42 dba.

Best for comparative is measure something like 8 in. from the inlet as interference factors fade into the background overwhelmed by the dominate source and provide a higher degree consistancy.

Calibrated nozzels can be bought for a few hundred dollars - if you are testing a narrow range you can get by with just a couple. Some plywood and a counterblower and you have an airflow test chamber

Re: Performance Vs Noise - Experimentation
 

"Some plywood and a counterblower and you have an airflow test chamber"
thats the stuff we need more of !!
start a thread ub, better yet jack this one