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PostPosted: Mon Aug 12, 2002 2:32 pm 
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I'm trying to design a multiple drive RAID enclosure that's relatively quiet. I can get Db specs on comps, but I was wondering: <BR> <BR>1. What sort of attenuation will I get when I put a fan INSIDE a case. (not an exhaust fan). <BR>2. What sort of attenuation will I get when I put a hard drive inside a plain 'ol enclosure. <BR> <BR>I realize I'm guestimating here, but this info will allow me to predict how loud my unit will be in the end. <BR> <BR>-Dore
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PostPosted: Mon Aug 12, 2002 2:32 pm 
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>>1. What sort of attenuation will I get when I put a fan INSIDE a case. (not an exhaust fan). <br>-- Some, maybe, but whether it gets noiser than outside the case depends on mounting details & positioning. <br> <br>>>2. What sort of attenuation will I get when I put a hard drive inside a plain 'ol enclosure. <br>-- Depends on the case & the drive. <br> <br>You'll have to be a lot more specific to get any useful advice from anyone. The HD quieting / cooling artilces and the new review of the Smart Drive here may help.
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>>>>1. What sort of attenuation will I get when I put a fan INSIDE a case. (not an exhaust fan). <br>>>-- Some, maybe, but whether it gets noiser than outside the case depends on mounting details & positioning. <br>>> <br> <br>Well, let's take for instance a cpu fan. Most cases have the cpu fan in about the same place. Is it alot louder outside of the box? By about how much? <br> <br>>>>>2. What sort of attenuation will I get when I put a hard drive inside a plain 'ol enclosure. <br>>>-- Depends on the case & the drive. <br>>> <br>>>You'll have to be a lot more specific to get any useful advice from anyone. The HD quieting / cooling artilces and the new review of the Smart Drive here may help. <br> <br>For instance, CompUSA has removeable hard drive cages like the Smart Drive. They don't advertise to be noise attenuating but I bet the drives are more quiet in them than outside. The only articles that i've found that show noise damping characteristics are for the Smart Drive, and we can't use that for our RAID. <br> <br>
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PostPosted: Mon Aug 12, 2002 2:32 pm 
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>>Well, let's take for instance a cpu fan. Most cases have the cpu fan in about the same place. Is it alot louder outside of the box? By about how much? <br> <br>In most cases, I don't believe the attentuation is much. Maybe 3-4 dB at best. Maybe more with a really well damped case that is lined with insulation on the inside. But the fan / HS mounting can allow vibrations to be transmitted into the case, which will then also add to the noise. The other thing is that a fan is essentially noise rated in free air, with nothing in the airflow path. As soon as there is some kind of obstruction in that airflow path close to the fan blades, say under 1.5-2", there is a very audible increase in noise caused by turbulence. A quiet fan directly mounted on a HS is much noisier than when it is simply held in free air. This is one reason the Zalman flower HS work quietly -- the fan is farther away, and somewhat decouple mounted. <br> <br>>>For instance, CompUSA has removeable hard drive cages like the Smart Drive. They don't advertise to be noise attenuating but I bet the drives are more quiet in them than outside. The only articles that i've found that show noise damping characteristics are for the Smart Drive, and we can't use that for our RAID. <br> <br>The higher frequency noise -- the whine -- is usually a bit less audible inside a case, but the lower frequency vibrations like the hum of the motor is often worse because of case / panel resonances. That's why decouple mounting of drives works so well. I am not familiar with these drive cages you mention. How about a URL? <br> <br>If I were building a large RAID drive box and wanted low noise, I'd probably do some kind of metal enclosure, apply panel dampening like Brown Bread on the ourside, decouple-mount at least one quiet fan (80-92mm 20 dBA fan at 5V) at the bottom blowing fresh air in via a duct to the outside, and have a vent on the top that allows the hot air to exhaust. Perhaps this latter could be fitted with another fan blowing out, through a vent straight out the back of the PC case. <br> <br>If you really wanted quiet, this internal box could be hanging off bungie cords or all the drives in it elastic mouted. Decouple mounting of a HD is really effective for noise reduction. Just try sitting a spinning bare drive on a piece of foam on a table, then on the table directly. The difference will astound you. That was my reaction the first time I heard this. <br> <br>My 2 cents; may not be applicable depending on your PC case -- bigger is easier to quiet & cool.

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Thanks for the info. If you're interested, the URL for the drive cage at compusa is: <br> <br><!-- BBCode auto-link start --><a href="http://www.compusa.com/products/product_info.asp?product_code=282701" target="_blank">http://www.compusa.com/products/product_info.asp?product_code=282701</a><!-- BBCode auto-link end -->
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>>Thanks for the info. If you're interested, the URL for the drive cage at compusa is: <br>>> <br>>>http://www.compusa.com/products/product_info.asp?product_code=282701 <br> <br>You're welcome -- I realized some of the text was nonsensical, so I went back to my last post and made some corrections. Should make more sense now. Writing without enough sleep, maybe. <br> <br>BTW, that link goes to a single removable drive enclosure -- I thought you said a multiple drive enclosure?
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You've been a great help. What I showed in (the URL) was a single drive cage. <br> <br>We will have multiple ones, and we have control over the design. Reason i showed you the CompUSA thing was that that enclosure must provide at least a little damping. <br> <br>our multiple drives will be very loud otherwise. <br> <br>-Dore
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