A Fan Muffler design

pswart · Post by **pswart** » Tue Aug 09, 2005 9:18 am

Hello,

I am designing a quiet case to hold both a Vapochill XE II unit and watercooling for the chipset and GPU. This is not going to be a small case - in fact it's going to be huge.

First things first - Fan Mufflers. Below a few pictures.

The idea is to cover the slats with a thin sound absorbing material to reduce sound but not to restrict airflow to much.

Any coments on the design welcome.

BrianE · Post by **BrianE** » Tue Aug 09, 2005 10:44 pm

Interesting, and it looks like it would be really large (like the project it's going with?).

Personally, I'm not sure if the small amount of sound absorbing material on the slats is going to do a whole lot. The more I read about sound absorbtion, the more I think you need to have more of it, and have it at least the thickness of the sound waves (so thicker would be better). Another thing is that sound is best absorbed by bouncing around off of surfaces, so I'd line the whole duct with foam (or whatever).

I can see where you're getting your idea though. I drew up some muffler designs a while back that had slats too, with the idea being that they wouldn't impede airflow very much. In the end though, I was drawing up more traditional muffler designs with boxy chambers and perpendicular walls inside. One problem I was encountering was the principle of blocking any direct lines between the noise source and the muffler exit. Early on I was getting a little mixed up between trying to block the noise (which doesn't really care where the air flows) and trying to almost filter or strain the noise out of the airstream like it were peas floating in water.

Keep in mind I haven't actually built anything yet (shifting priorities and all

) but that's just how I understand it.

datapappan · Post by **datapappan** » Wed Aug 10, 2005 12:28 am

I think your design is overdone, sorry. The fins in that duct will take away a lot of air flow (or rather have great impedance), and the sound will also take other ways to your ear.

My experience with noise damping is that it's easier to aim at not producing the noise in the first place, and if you want to dampen noise you have to really contain the noise. This means the fan and both its intake and exhaust has to be housed in something with thick enough insulation as to dampen good, and also sturdy enough as to not let anything through, but rather bounce the sound waves back through the insulation again.

I've also experimented with ducting the CPU HSF, only to find that the positive effect of bringing cooler air to the HSF is countered by the larger impedance of the duct, resulting in lower air flow. Effect on temperature of the CPU has been marginal, and noise wasn't affected either. YMMV.

As for mufflers, best bet is to make an insulated chamber, as I believe the above poster is referring to. Bear in min though that noise will find other routes, i.e. the opposite direction and out through the case cover.

HTH, datapappan

xenithon · Post by **xenithon** » Wed Aug 10, 2005 4:32 am

Welcome! Great to see another South African (recognise the drawings from V9

)

Like I said there, I think it seems a bit too complex and large. Check out silverstone's PP02 for ideas - the size is not mandatory as it is totally lined with acoustic dampening material. Your design resembles a duct more than a muffler, so perhaps you might consider building a duct rather, and appending a muffler at the end.

Cheers,
X

IsaacKuo · Post by **IsaacKuo** » Wed Aug 10, 2005 6:45 am

I really don't think this design will significantly reduce noise, and it could actually increase noise by forcing the fan to work harder. A more traditional bulkier muffler design would be more effective, but most effective of all is to use a silent fan in the first place.

I notice that the slats have the opposite of the intended effect--they leave relatively straight pathways for sound to escape, while impeding airflow with a lot of undesirable turns. It would be more effective to have the slats mounted parallel to the (curving) airflow. These could even help guide airflow smoothly, while blocking straight sound pathways. But the point is moot because such thin slats wouldn't have much effect on sound anyway.

datapappan wrote:I've also experimented with ducting the CPU HSF, only to find that the positive effect of bringing cooler air to the HSF is countered by the larger impedance of the duct, resulting in lower air flow. Effect on temperature of the CPU has been marginal, and noise wasn't affected either. YMMV.

The main benefit of a CPU duct is not to improve temperatures, but to indirectly reduce noise--by allowing you to remove the CPU fan entirely. I've had 100% success so far with CPU ducting/fan removal to reduce noise; I'm sure the CPU always got hotter in the process.

pswart · Post by **pswart** » Wed Aug 10, 2005 9:28 am

Thanks for all the replies.

I have taken the design further - remember I said in the beginning this is going to be a big case.....

The picture below shows mufflers with reduced number of slats and the water-cooling radiator suspended on vibration absorbing material - the picture does not actually show this nor the fan's. You will have to use your imagination.

The "box" is covered in a sound absorbing material and the thickness of this will ultimately determine the size of the box.

The inside of the mufflers and the slats will also be covered with thinner sound dampening material.

From all your replies it seems that I will have to build this and test the various alternatives.

PS. I like the simplicity of the Silverstone PPo2 PSU muffler.

IsaacKuo · Post by **IsaacKuo** » Wed Aug 10, 2005 9:39 am

Your slats are still a bad idea. They'll just impede airflow while having minimal effect on noise--they're even angled to allow a perfect straight path for noise to escape!

Take a look at Bluefront's muffled SuperLANBoy (in the main website), for a good idea for a muffler design. His bottom muffler has a row of large compartments, connected to each other with sections of PVC pipe.

Anyway, the purpose of this muffler is a little puzzling. A radiator shouldn't be making any significant noise. Do you have a noisy pump which is integral to the radiator?

pswart · Post by **pswart** » Wed Aug 10, 2005 9:44 am

IsaacKuo wrote:Your slats are still a bad idea. They'll just impede airflow while having minimal effect on noise--they're even angled to allow a perfect straight path for noise to escape!

Take a look at Bluefront's muffled SuperLANBoy (in the main website), for a good idea for a muffler design. His bottom muffler has a row of large compartments, connected to each other with sections of PVC pipe.

Anyway, the purpose of this muffler is a little puzzling. A radiator shouldn't be making any significant noise. Do you have a noisy pump which is integral to the radiator?

Thanks. I just want to build a "silent" case. Remember that I also have a Vapochill unit that's not silent by any standard.

BrianE · Post by **BrianE** » Wed Aug 10, 2005 11:11 am

Wow, nice pictures.

Are the fans supposed to be mounted on either end of the slatted ducts? If this is the plan, and you have the space to make a huge box like this, I would suggest that you instead soft mount either two fans in parallel infront of the radiator, or series mount two fans infront and behind it, inside the box closer to the radiator. Bluefront's foam mounted fans in his muffler box are a start (I'd make it softer though).

Like IsaacKuo said, get rid of the slats. I'd also think about reshaping the ducts, maybe to something wider and closer to the box. Basically just adjust the dimensions of it so that it doesn't become too restrictive (volume-wise), but so that you couldn't see the noise source if you look down into it. Moving the fans inside the box away from the ducts like I mentioned above would help do this. You'd still have to line the ducts with absorbtion material as well though.

pswart · Post by **pswart** » Wed Aug 10, 2005 12:16 pm

Another design approach based on a mod I saw on silentpcreview.com.

This is a muffler in the correct sense of the word.

I would appreciate your thoughts on the sound absorption and airflow characteristics of this design over the previously mentioned ones.

As far as layout is concerned these are just concepts, once I have something that seems ok I will work on the best possible layout to be both effective and save space. Any ideas welcome!!

Here it goes:

Thanks!!

Bluefront · Post by **Bluefront** » Wed Aug 10, 2005 1:33 pm

This last design is a copy of my original muffler attempt.....posted here somewhere. It works very well but has to be big for sufficient airlow.

Here's one of my later designs using a similar setup. In this one I put the PSU (all fans removed) at the exit point of the airflow.

I swear this is where Antec got the idea for the P-180. Works well but you'll have problems with the length of the ATX cables, much like the Antec design.

BrianE · Post by **BrianE** » Wed Aug 10, 2005 9:58 pm

Looks better to me, although it just occurred to me that if you're running parallel fans you'll want to try and make the muffler holes a LOT bigger. Personally I'd just switch the setup to series orientation and avoid that kind of thing.

The mufflers will add resistance too, so that might be wiser anyhow.

Another thing is if you do decide to go with that muffler design, or something similar, I sat down one day and did some math for the areas of the tubes. I figured out that the 4 smaller tubes would have to be larger than that, or you'd have to have more of them. Sorry I wish I could find my notes on this, but it was surprising how much larger they needed to be.... I think it was something like four 3" tubes to equal one 4" tube or something like that.

Also, finally - the secret location of Bluefront's other gallery! Woohoo!

pswart · Post by **pswart** » Thu Aug 11, 2005 11:45 am

BrianE wrote:Looks better to me, although it just occurred to me that if you're running parallel fans you'll want to try and make the muffler holes a LOT bigger. Personally I'd just switch the setup to series orientation and avoid that kind of thing. The mufflers will add resistance too, so that might be wiser anyhow.

Another thing is if you do decide to go with that muffler design, or something similar, I sat down one day and did some math for the areas of the tubes. I figured out that the 4 smaller tubes would have to be larger than that, or you'd have to have more of them. Sorry I wish I could find my notes on this, but it was surprising how much larger they needed to be.... I think it was something like four 3" tubes to equal one 4" tube or something like that.

Also, finally - the secret location of Bluefront's other gallery! Woohoo!

Please explain "series orientation"..

BrianE · Post by **BrianE** » Thu Aug 11, 2005 5:44 pm

pswart wrote: Please explain "series orientation"..

Sorry for not being clear. "Series" basically means putting them one after another in line, so in this case you would probably put one fan before the radiator and one after it. Another example would be a typical case fan layout with one intake and one exhaust fan. It's supposed to help with higher resistance setups because the two fans share the sucking/blowing workload between them. The tradeoff is that you don't get as much airflow as you would with running two fans side by side (parallel), but that is only supposed to work well with very little resistance. Hope that explains things better.

vertigo · Post by **vertigo** » Sat Aug 13, 2005 3:47 am

Well if you look at motorbikes, a small muffler makes a huge difference. I would think that a small muffler could work sufficiently well.

If you think of a speaker, reflections in the box impacting on the cone create distortion, but to eliminate that damping material or oblique sides are used. There are no slats in speaker boxes.

bobo5195 · Post by **bobo5195** » Sat Aug 13, 2005 3:54 am

might want to check formfactors.org and the btx spec has abit on slats and how they effect noise on there.

From an effor point of view it might be easier to just use many quite fans in the first place.

Bluefront · Post by **Bluefront** » Sat Aug 13, 2005 5:48 am

Effort aside......if you want the quietest exhaust, a muffler of some sort is the answer. And if you can incorporate the PSU exhaust into the design, all the more better.

That last link I posted was my first attempt at this sort of muffler. Later designs resulted in a one-fan computer, with a fanless PSU (in the normal position) being last in the airflow path, with a muffled airflow track.

What I'm using now is a modified version....with the PSU and the rest of the computer dumping airflow into a common muffled track. These are all custom modified cases, costly in time, but worth it for the sound-reduction benefit.

pswart · Post by **pswart** » Sat Aug 13, 2005 11:37 am

Hi,

Below some more sketches - this time of the complete case design idea.

The top "muffler unit" will house the vapochill and the bottom one the water cooling setup.

The hard disk unit and the PSU still poses a problem as to how to incorporate them into the silent theme.

Airflow over the mother board is also something I still need to think on.

The cable length from the mother board to the optical and other drives also concerns me.

Any suggestions welcome!!

http://i14.photobucket.com/albums/a326/ ... e/COMT.jpg

http://i14.photobucket.com/albums/a326/ ... e/COMF.jpg

http://i14.photobucket.com/albums/a326/ ... e/COMB.jpg

IsaacKuo · Post by **IsaacKuo** » Sat Aug 13, 2005 12:48 pm

Honestly, those sketches remind me of the sort of fanciful thing I'd post about when I was new here at SPCR. It "feels" like the designer is inexperienced and hasn't done much in terms of actually building quiet systems to have an idea of what works and what doesn't.

For example, the internal layout may look straightforward in a 3d modeler, but it's going to be a headache to put together and maintain just based on the cabling alone. There's a ton of wasted space for no good reason. With such a large case, there's no reason to NOT have all components easily accessable from one side. Also, there's no reason to recess the ATX backplane and expansion card backplanes within the box where it's not easily accessable.

The airflow design is also very inexperienced. It looks like the CPU, GPU, and northbridge are entirely outside the main airflow path. This is BAD. Also, with such a large amount of space, there's no good reason to cram those hard drives side-by-side-by-side so densely packed that they'll cook each other.

Besides, a computer with 4 3.5" hard drives isn't going to be quiet enough to be worth the effort/bulk/weight of that massive muffler system anyway. You might get somewhere with a special muffler system dedicated to JUST the hard drive array, but this is definitely a challenge.

Basically, hard drives need to run very cool, but they don't actually generate much heat (compared to other computer components). As such, they need fresh air but tolerate low airflow. By putting the array and its cooling fan within a heavily soundproofed enclosure, you only need a relatively small intake and exhaust to provide adequate airflow. This is good for the hard drives, but the low airflow amount won't be very useful for cooling anything else in the computer. Fortunately, the other computer components can and should be designed to not make much noise in the first place.

Actually, any sort of muffling or sound dampening is hard for a novice to do. The best thing is to just try building something simple and seeing how effective (or more usually NOT effective) it is. I learned ten times as much from building my first scratchbuilt case than I ever did theorizing and asking questions here on SPCR. My second scratchbuilt is still going strong as my main workstation.

I guess what I'm trying to say is: Give up right now any hope that you're going to "get it right" the first time. Consider your first case as nothing more than a prototype to learn how to make the second case. Don't worry about making it look pretty, just slap something together and then mess around with it.

BrianE · Post by **BrianE** » Sat Aug 13, 2005 1:08 pm

HOLY COW!!!

Are you serious? I just noticed (now...) that you're using both a Vapochill AND a watercooler. I guess you're after maximum overclocking ability too... very ambitious.

Seeing as how everything looks custom-made, I'm sure you can find some way to fit a PSU in there... maybe in the exhaust airstream in the top or bottom muffler. You could probably soft-mount everything too, while you're at it (including optical drives).

I don't know how large the various radiators are, but if you're planning something that big there must be a way to have both the intake and exhaust on the rear of the case, pointing away from each other. Maybe by making the mufflers a skinnier design and placing them side by side and then have the air stream make a U-turn past the radiator closer to the front. At least then you wouldn't have any openings facing you.

I wouldn't try to emulate engine mufflers too closely unless they're the ones that basically add up to a tube lined with noise dampener (which aren't as effective though). They work at much higher pressures than computer fans, so can overcome some of the more highly restrictive designs like your typical car muffler. They also use techniques such as noise cancellation, which I wouldn't even try to duplicate.

BrianE · Post by **BrianE** » Sat Aug 13, 2005 1:16 pm

IsaacKuo wrote: The airflow design is also very inexperienced. It looks like the CPU, GPU, and northbridge are entirely outside the main airflow path. This is BAD.

Psst... he's not air-cooled....

Hopefully this is just a rough concept sketch and he can squish things together a bit better later on. I understand what you mean about not "getting it right the first time", though.... it may be worthwhile to build some future adjustability into those plans.

I imagine I'll be running into the same "first time" issues not once, but twice over the next year.

I try to compensate by researching things to death, but the more I get into actually building parts of it, the more little issues, possible problems, and real-world issues I run into....

Bluefront · Post by **Bluefront** » Sat Aug 13, 2005 1:55 pm

I'll have to agree with Issac.....these sorts of things are "learn as you go". I think my first muffler setup involved cooling the hard drives only (link). I quickly found I only needed a quiet 80mm fan blowing out the rear to keep them cool.

I also found that everything was much easier if I mounted the drives in a movable drawer......which made me use a 36" IDE cable (worked ok). As I progressed with this, I found lining the wood case with thin acoustic foam did help. When I finished the hard drives were inaudable, and I had to put my ear close to the rear fan to hear it at all. Took a while to get it right....

DG · Post by DG » Sun Aug 14, 2005 3:54 am

Speaking of mufflers, what do you think of this intake muffler:

The air will enter by the lateral sides of the muffler, on the left and right. It will be covered with some damping material.

Bluefront · Post by **Bluefront** » Sun Aug 14, 2005 5:59 am

IMHO.....It's quieter if you don't have any fan at the intake opening, but rather use an exhaust fan(usually at the rear) to suck through an intake.

And it's better to have intakes at the lower rear or the bottom of the case...anyplace but the front. I'm assuming you have a choice in the matter....you're building your own.

pswart · Post by **pswart** » Sun Aug 14, 2005 9:08 am

IsaacKuo wrote:Honestly, those sketches remind me of the sort of fanciful thing I'd post about when I was new here at SPCR. It "feels" like the designer is inexperienced and hasn't done much in terms of actually building quiet systems to have an idea of what works and what doesn't.

For example, the internal layout may look straightforward in a 3d modeler, but it's going to be a headache to put together and maintain just based on the cabling alone. There's a ton of wasted space for no good reason. With such a large case, there's no reason to NOT have all components easily accessable from one side. Also, there's no reason to recess the ATX backplane and expansion card backplanes within the box where it's not easily accessable.

The airflow design is also very inexperienced. It looks like the CPU, GPU, and northbridge are entirely outside the main airflow path. This is BAD. Also, with such a large amount of space, there's no good reason to cram those hard drives side-by-side-by-side so densely packed that they'll cook each other.

Besides, a computer with 4 3.5" hard drives isn't going to be quiet enough to be worth the effort/bulk/weight of that massive muffler system anyway. You might get somewhere with a special muffler system dedicated to JUST the hard drive array, but this is definitely a challenge.

Basically, hard drives need to run very cool, but they don't actually generate much heat (compared to other computer components). As such, they need fresh air but tolerate low airflow. By putting the array and its cooling fan within a heavily soundproofed enclosure, you only need a relatively small intake and exhaust to provide adequate airflow. This is good for the hard drives, but the low airflow amount won't be very useful for cooling anything else in the computer. Fortunately, the other computer components can and should be designed to not make much noise in the first place.

Actually, any sort of muffling or sound dampening is hard for a novice to do. The best thing is to just try building something simple and seeing how effective (or more usually NOT effective) it is. I learned ten times as much from building my first scratchbuilt case than I ever did theorizing and asking questions here on SPCR. My second scratchbuilt is still going strong as my main workstation.

I guess what I'm trying to say is: Give up right now any hope that you're going to "get it right" the first time. Consider your first case as nothing more than a prototype to learn how to make the second case. Don't worry about making it look pretty, just slap something together and then mess around with it.

Thanks for the comprehensive feedback.

As to the designers experience levels as far as building silent chassis - Yep nothing.

As to knowing what works and what does not - nothing. You see that’s the point. I am testing all the "designs" I make to determine the best solution.

Like you say one learns more from this type of experimenting than sketching a few ideas.

The layout. Yes well this, as I mentioned is not the final layout. Just an attempt to understand the "space" in real terms. As to recessing the ATX backplane and expansion card backplanes two reasons. Remember I have a Vapochill unit - it can only reach that far.... Secondly the idea is to seal of the openings. No doubt a seasoned silent system builder knows that any hole defeats any attempt to reduce sound.

Airflow. In the design above there's no airflow over the MB etc. I still need to ponder on this. Also remember that the GPU, Chipset is cooled by water. The CPU does not need any airflow - it's not cooled by air, however, the Vapochill does this job.

Hard Drives. Yep the won't be housed as shown in the sketch. Like you said - There's ton's of space..

This is a prototype design that will eventually mature into a prototype build that might, might not be successful. Part of my "slapping" something together just happens to be a few sketches.

Thanks for the reply.

Some pointers would be nice!!

DG · Post by DG » Sun Aug 14, 2005 9:57 am

Bluefront wrote:IMHO.....It's quieter if you don't have any fan at the intake opening, but rather use an exhaust fan(usually at the rear) to suck through an intake.

And it's better to have intakes at the lower rear or the bottom of the case...anyplace but the front. I'm assuming you have a choice in the matter....you're building your own.

Hehe, that's exactly what i want to do.

See here: http://forums.silentpcreview.com/viewtopic.php?t=24605
You're welcome to post some opinions there for my silence project. The feedback there is kinda inexistent 'till now...

andywww · Post by **andywww** » Sun Aug 14, 2005 11:29 am

There was a post a while back from someone who tried to block the noise of a side panel fan in much the same manner as your intake muffler- he put a panel in front of the fan hole with a few inches clearance. It didn't work out very well, drastically reducing airflow.

IsaacKuo · Post by **IsaacKuo** » Mon Aug 15, 2005 8:35 am

pswart wrote:As to recessing the ATX backplane and expansion card backplanes two reasons. Remember I have a Vapochill unit - it can only reach that far....

I'm not familiar with the Vapochill unit, and don't understand what you mean by "reach that far". If you can't move the motherboard further back, then you can surely move the rear of the case forward.

pswart wrote:Secondly the idea is to seal of the openings. No doubt a seasoned silent system builder knows that any hole defeats any attempt to reduce sound.

But there isn't any hole. The ATX backplane itself seals off any hole.

pswart wrote:Airflow. In the design above there's no airflow over the MB etc. I still need to ponder on this. Also remember that the GPU, Chipset is cooled by water. The CPU does not need any airflow - it's not cooled by air, however, the Vapochill does this job.

Okay, I missed this. Still, I think you should place the motherboard against one of the box's sides. Besides being easier to mount (you just screw the mobo to the side of the case), it keeps everything on the mobo easy to access. In other words, I recommend a traditional placement of the mobo.

pswart wrote:Hard Drives. Yep the won't be housed as shown in the sketch. Like you said - There's ton's of space..

My recommendation for a layout is something like this:

Code: Select all

 __________________
<           optical|
<      muffler     |
<______............|
|      radiator|   |
|mobo          |   |
|mobo          |PSU|
|mobo          |   |
|mobo          |___|
|mobo    |.........|
|mobo    | H H H H |
|mobo    | D D D D |
|________|.........|
>                  |
>      muffler     |
>__________________|

This is a view from the left side, with the left side of the case open. The hard drives are mounted vertically between two grills with stretch magic, so that the cable ports are toward you. Thus, it's easy to plug or unplug the hard drives. In fact, every plug and port is easily accessable, except perhaps for the power cord (the power cord probably needs to be a 90 degree bend cord).

Notice that the "first in line" of airflow are the hard drives--these hardly heat up the air but require the coolest air. The PSU and radiator then share the negligibly heated air side-by-side to the exhaust muffler. This PSU hangs from the top of the box via the standard mounting holes.

Other than the unconventional position for the PSU, this is similar to a conventional case layout. It should be relatively compact and narrow, limited by the width of the optical drive (like any other mid/full tower case).

pswart · Post by **pswart** » Mon Aug 15, 2005 1:08 pm

Hello,

Thanks for all the replies.

IsaacKuo below a link to the Vapochill Unit. I have the XE II. The case it comes with is very restrictive - no space!! I am going to build just the Vapo Unit into the custom case.
http://www.asetek.com/default.asp?showP ... &menuID=-1

I think my imagination got the better of me

. Please don't all break into an uncontrollable fit of laughter!!!

Yep I did it again.... Spent some time sketching again.

I manage (IsaacKuo you especially should prepare yourself for this one!!) to incorporate all the suggestions into what I now believe is going to be the first prototype. Of course even before I start on this I will test the ideal dimensions - with specific reference to the "muffler's".

As always I would appreciate any comments!!!

http://i14.photobucket.com/albums/a326/ ... htSide.jpg

http://i14.photobucket.com/albums/a326/ ... FTSIDE.jpg

http://i14.photobucket.com/albums/a326/ ... USTFAN.jpg

http://i14.photobucket.com/albums/a326/ ... te/TOP.jpg

Thanks!

BrianE · Post by **BrianE** » Mon Aug 15, 2005 8:33 pm

I'm not sure if it's just that my opinion differs, or if Isaac didn't realize what your two separate active coolers entail... or if that's not what he meant(? I'm a bit confused!) but I don't think you need to route ALL the air through the case like that. Maybe just the PSU pulling air through the hard drives and motherboard? In any case I definitely wouldn't have an intake fan on the front.

Anyway, this is what I kind of meant in my previous post. (Is there a trick to using the /code tag? This lousy diagram took forever to tweak!

) Lay one of these on the top of the case, and one on the bottom. This is a top view and is more squished looking than what I imagined. Don't know if this helps or just makes things worse!

Code: Select all

___________________________
|            |            |
<            |            <
<   OUT      |     IN     <
<            |            <
|_____       |      ______|
|            |            |
|            |            |
|      ______|______      |
|            |            |
|            |            |
|___F-A-N____|___F-A-N____|
|            |            |
|            |            |
|=====R-A-D-I-A-T-O-R=====|
|                         |
|                         |
|\                       /|
|_\_____________________/_|

A Fan Muffler design

A Fan Muffler design

The Complete case design idea - Work in progress

Possible Muffler