Solved How to dampen server noise?

[DiscmanDaemon]

For reasons of economy, a number of servers for my startup have found a comfortable home in a walk-in closet in my home. While I do not mind the constant whirring of the fans and disks (the sound of a hard-working server is music to my ears), and crisis response time is at an all time low, visitors seem to find the noise irritating and it certainly disrupts dinners, movie nights, etc.

Does anyone have any ideas/experiences on how to quiet a rack of servers without decreasing performance, and with a limited budget. I've heard of people switching out the fans for custom, quiet fans, and replacing spinners with SSDs, but given that there are six 1u servers, each with two 500 GB drives, this would be rather expensive. I've heard of people applying various things to the walls to dampen the noise and considered padding the walls with blankets or something similar, but I worry about dust.

The solution does not have to be permanent, as the servers only need to quiet down when I have guests over, but it must be cheap (ideally less than 100 dollars), and cannot impact performance since I never know when the load will spike. Any ideas or experiences you have to share would be much appreciated.

 

[Deleted member 9563]

I'm guessing that the closet is not very tight and that's why the noise is getting out. Perhaps tighten it and vent it towards another less inhabited area - like with a fan there. The high frequency of fans is not hard to dampen in other ways. A relatively thin layer on the walls of the closet can dampen it. Particularly on the back where it might reflect back out. That should get you a couple or 3db cut. Not much, but I think the only effective way really is going to be airtight doors and separate venting, and that is likely to cost - if not money, then quite a bit of work.

 

[DiscmanDaemon]

You are correct that the closet door is very leaky for both noise and air, but fortunately it opens to my workshop area where its not a problem. The bothersome noise is coming through the shared walls with the living room and the bedroom. When you suggested a layer behind the servers on the walls, are you suggesting the sound-proofing foams sold commercially or something else?

Thanks for your help!

 

[Datapanic]

Buy a nice hifi music setup and put on some tunes!

 

[scrappywan]

Dense materials such as thick drywall does a pretty good job attenuating high frequency noises at a minimal cost. You could build something like a drywall front cover to your closet to reduce the server noise, but you'll need to figure out good ventilation as well.

 

[Deleted member 9563]

When you suggested a layer behind the servers on the walls, are you suggesting the sound-proofing foams sold commercially or something else?

Sure that would work, but it is indeed easy to absorb higher frequencies, which I assume it is the problem here. So, acoustic tile, or that fiberglass board they use in lowered ceilings, or anything else "foamy" that's cheap. It will atleast keep the reflections down, and that is a component of the overall sound.

However, if it's going through the wall then I'm suspecting that there is a vibration component which is a much lower frequency than the wind sound. To stop that will take more mass. you could use a double wall. That's not as troublesome as it sounds. Plaster board is heavy and cheap. The mounting is a bit difficult though, as it needs to be isolated (not touching) from the next (conducting) wall as much as possible. Either separate studs, which is studio style and probably overkill here, or just supporting it on the edges or perhaps a narrow strip of wood in the middle. Plywood is also good for middle frequencies, but the plaster board is a very good material for acoustic work because of its weight.

The other thing is that a vibration would be generated by unbalanced fans. Perhaps there are better fans, but if rubber mounts for the fans are possible you could cheaply remove much of the vibration (sound) right at the source where's it's being conducted in the first place. There are many rubber mounted fans available in the desktop world, but I'm not sure what is available to fit your severs.

 

[DiscmanDaemon]

Buy a nice hifi music setup and put on some tunes!

This solution has been both implemented and tested. It is certainly efficacious in many cases, particularly with TV shows (we discovered Beavis and Butthead laughing over a 5.1 system really seems to negate the server noise). However, there are a few edge cases where the sound system is nonviable, for example, a romantic candle-lit Valantine's night dinner.

Dense materials such as thick drywall does a pretty good job attenuating high frequency noises

I'm suspecting that there is a vibration component which is a much lower frequency than the wind sound. To stop that will take more mass. you could use a double wall

This may be the way to go. If mass is the key factor here, am I correct in assuming cinderblocks may work as well if not better? I have a large supply of them on hand, and it seems more appealing than drywall since I could assemble a cinderblock wall without making a great deal of dust (and having to shut down and move the servers). There is solid foundation under the floor so the weight isn't a problem. Would it also be worth analyzing the frequency of the noise to pinpoint the optimal material?

There are many rubber mounted fans available in the desktop world, but I'm not sure what is available to fit your severs.

I will look into this also. They are run-of-the-mill 1u Supermicros so parts should be readily available.

Thanks for all the ideas! I think we are heading for a much quieter weekend.

 

[Deleted member 9563]

Cinderblock is great stuff, but it does have to be tight. Cracks can pass a surprising amount of sound.

Would it also be worth analyzing the frequency of the noise to pinpoint the optimal material?

Perhaps, if it's not too difficult. I'm just going on a lot of sound experience here, but of course don't know what it is exactly that you are hearing there or what frequencies bother you.

As a quick reference, wind sound, like a woosh, is composed of very high frequencies. The vibration of motors or fans going around is going to be much lower and would be classified as mid frequencies. Say in the 500Hz to 5kHz range. Drywall is great for that. I doubt you have much low, like bass frequencies. Those will definitely require some real mass and the only way there is a true double wall with separate studs, or the cinderblock if it's solid and sealed at the sides.

Edit to add: the thin covering I first suggested is for very high frequencies only. Like the woosh or wind sound. People often waste their time with "acoustic treatment" like egg boxes and acoustic tile and all they're doing is killing a few very high frequencies and the noise is still there in force. The reason that curtains often work well in a room is because there is a space behind them, so it works "twice" and also becasue the resonance space effects lower frequencies much more than if the cloth was right on the wall. There's a lot of math here if you want to get really involved.

 

[PacketMan]

When I stream Iron Maiden from my FreeBSD nas, through my PS3 with my amplifer knob on 7 I find I can't hear my server at all, and anything thing else for that matter.

"I'm running free yahhh I'm running free...."

 

[DiscmanDaemon]

doubt you have much low, like bass frequencies. Those will definitely require some real mass and the only way there is a true double wall with separate studs, or the cinderblock if it's solid and sealed at the sides.

After analyzing the frequencies, I have found that while the servers themselves seem to produce the most noise at around 500-600 Hz range, when measured on the other side of the wall (what is coming through the wall), it the dominant frequencies are very low (200 to 300 Hz range). I suspect a lot of this noise of these frequencies is coming from the vibration of the spinning disks (each server has 2x 10,000 RPM disks) and the two layers of drywall seem to be attenuating the noise down to the low frequencies. It looks like putting a secondary (cinderblock) wall up is going to be my weekend project.

When I stream Iron Maiden from my FreeBSD nas,

Your idea of using the server as part of a system to drown out the server noise is intriguing. I wonder if its possible for a server to calculate the noise it's making and generate and stream the appropriate destructive frequency to actively cancel the noise. If someone wants to develop this application, I will be your first beta tester.

 

[phoenix]

Have you tried hanging some thick quilts or duvets or other blankets on the outside wall where the noise is coming through? Just call it modern art. Or, if there's room, you can do the same on the inside wall of the server closet. A 2" thick wool blanket cuts down on a lot of sound.

One thing you need to be careful of is not blocking the venting for the servers. To make a really sound-proofed room, you have to make it fairly airtight. Servers tend not to like it when there's no air circulation around them. But vents can also carry sound.

 

[drhowarddrfine]

Put egg cartons on the wa....no. Do not put egg cartons on the wall. We tried this a hundred years ago at a small, cheap radio station's newsroom and it didn't work at all.

 

[obsigna]

After analyzing the frequencies, I have found that while the servers themselves seem to produce the most noise at around 500-600 Hz range, when measured on the other side of the wall (what is coming through the wall), it the dominant frequencies are very low (200 to 300 Hz range). I suspect a lot of this noise of these frequencies is coming from the vibration of the spinning disks (each server has 2x 10,000 RPM disks) and the two layers of drywall seem to be attenuating the noise down to the low frequencies. It looks like putting a secondary (cinderblock) wall up is going to be my weekend project.

I suspect that a good part of the noise from disk vibration is not transferred via air but by passing the vibration via physical contact of the disks to the 1U housings to the rack to the ground and the wall which finally acts like a speaker membrane.

I suggest to check wether you can place thin weak silicon rubber sheets between the disk and the supporting trays in the server, thicker sheets of foam rubber between the 1U housings and the rack and gross polyurethane foam on the base underneath of the rack. Neither screw mount the 1U housings into the rack nor the rack on to the wall and/or the ground.

 

[DiscmanDaemon]

Results are in from trying some of the latest suggestions:

sheets of foam rubber between the 1U housings and the rack and gross polyurethane foam on the base underneath of the rack

This was effective in reducing the noise by about 2 dB with just sheet rubber I had on hand. I suspect I could do better with purpose-bought materials. Should work in synergy with the other solutions.

A 2" thick wool blanket cuts down on a lot of sound

Another 2 or 3 dB saved right there. People hang tapestries on their wall so why not a goose-down comforter I did not put blankets inside the closet with the servers though since they seem to shed and breathing dust/feathers are not going to be good for the servers.

One thing you need to be careful of is not blocking the venting for the servers. To make a really sound-proofed room, you have to make it fairly airtight. Servers tend not to like it when there's no air circulation around them. But vents can also carry sound.

This is an important word of caution. I am lucky in that the door to the server closet opens to an area where noise is not an issue, but an important design consideration for anyone putting a noisy server rack in their home.

So far with rubber sheets and two goose-down comforters, the noise down to about 40 dB, and I have high hopes for the second wall taking it down even further.

 

[DiscmanDaemon]

An update:
A combination of goose-down comforters, sheet rubber, and a secondary cinderblock wall on two sides of the server rack has brought the offending noise down to less than 30 dB, which is hardly noticeable, without hindering ventilation. A thank you for all the excellent advice and for assisting in restoring quiet to my home.