second skin VS dyanmat

Enclosures and acoustic damping to help quiet them.

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iakovl
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second skin VS dyanmat

Post by iakovl » Tue Mar 18, 2008 1:07 pm

what should i use for my case?
second skin - damplifier-pro
dynamat - dynamat xtreme

FlorisNielssen
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Post by FlorisNielssen » Wed Mar 19, 2008 3:02 am

They both weigh 2,2 kg/m2, but the damplifier pro is a little thicker, which makes the Dynamat denser.
Higher density is better, so you should probably choose the Dynamat.

lor77
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Post by lor77 » Wed Mar 19, 2008 3:32 pm

Hi ,
There are a lot of products in Dynamats web page.
Which product will be more applicable for a spcr member.
I mean Dynamat extreme vs DynaPad vs Dynaliner?
What combined solution would be for maximum performance sound wise?
http://www.dynamat.com/technical_technical.html
It has to be only higher density products equal better performance?

jeffc
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Post by jeffc » Sat Mar 29, 2008 3:15 pm

I would recommend Dynamat Xtreme first, then maybe one of the foam types over it for possibly unnecessary overkill. Dynamat Xtreme is what Dynamat itself sells for computer case damping, so Xtreme is what they think is the right one to use.

lor77
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Post by lor77 » Sun Mar 30, 2008 3:44 am

Thanks for the recommendation jeffc.
Doing a more throughout reading in the forum i concluded your idea is the most applicable.Vibration dampening first using Dynamat and then Foam from Sonex acoustics(even though im vibration free).
I will be able to find Dynamat in a local car shop,doubt it about Sonex one.
What about the AcoustiPack™ Deluxe?In which category does it fall in?My guess will be under the vibration dampening.
Thanks again.

jeffc
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Post by jeffc » Sun Mar 30, 2008 4:14 am

The foam based ones are usually for reducing noise in the air inside the case. So AcoustiPack is probably more for sound dampening than vibration dampening. Some of the Dynamat foam materials are probably also for sound dampening.

lor77
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Post by lor77 » Sun Mar 30, 2008 7:23 am

Thanks again jeffc for your recommendations.
Nice to clear that out.

iakovl
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Post by iakovl » Sun Mar 30, 2008 1:50 pm

thats why i gonna use SS and Sonex

jhhoffma
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Post by jhhoffma » Mon Mar 31, 2008 7:15 am

jeffc wrote:The foam based ones are usually for reducing noise in the air inside the case. So AcoustiPack is probably more for sound dampening than vibration dampening. Some of the Dynamat foam materials are probably also for sound dampening.
Err, sound is vibration. What I think you meant is that open-cell foam-based products are better at attenuating high pitched frequencies (caused by high-speed components) than the low frequency resonances. The foam based products can be thought of in two ways. One they are good for providing an uneven surface to prevent direct reflection of sound waves and instead dispersing and diffusing them, reducing the perceived sound. Two, the cushier kinds of foam can act as a isolation barrier when placed (or wedged) between a vibrating source and a mounting surface.

Dynamat is made with high density (usually butyl) rubber materials that increase the mass of case panels and thus increasing the energy required to induce resonance vibration. Since the vibrational energy going to the panel will not increase, this reduces the amount of resonance (as well as the frequency of the resonance) resulting in less noise.

I won't waste my money on Dynamat or Acoustipack. You can do the same thing yourself with a little effort. I've found the best combination is with self-adhesive vinyl floor tiles and automotive headliner fabric. The floor tiles can usually be picked up at most home improvement stores. The headliner fabric I get a JoAn's fabrics. It's made up of a layer of open -cell foam laminated to a felt-like fabric. It's a little pricey but you don't need much. Total I spent on my case ($12): $9 for a yard of headliner material and $3 for 3 tiles (on sale).

lor77
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Post by lor77 » Mon Mar 31, 2008 1:45 pm

Very enlightening indeed jhhoffma.
So to summarize,
Closed type foam is mainly best for reducing low pitched frequencies or better reduce resonance vibration whereas Open type foam is for high pitched ones(as you said high speed components produce this, such as hard drives seeks noise)
So firstly how much vibration resonance is made by a spcr system.My guess is not so much since most of as use some kind of fan\hd mounting or fan rpm lowering technique so that not so much vibration is induced.
Secondly and most importantly and correct me if im wrong we have the high pitched frequencies produced mainly from hard drive mechanics or\and high speed component(ex. high rpm fans) and this is the point where we can dampen more.
So that open type foam is preferred for making a more pronounced db decrease in our system even if that will be slight.

Your thoughts will be highly appreciated.

ps.Just realized that using both type of foam is an overkill that will not make a impact in sound reducing.

Plekto
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Post by Plekto » Mon Mar 31, 2008 2:17 pm

http://secure.data-comm.com/GL/Detail.bok?no=241601

This stuff works better for a lot less money. It's most commonly seen for drum pad silencing. This place isn't the least expensive, either. But it's WAY cheaper than Dynamat.

jeffc
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Post by jeffc » Mon Mar 31, 2008 9:58 pm

Vibration usually means vibrations within solid materials. Sound usually means vibrations in air (or liquid). They're both vibrations, but the materials and techniques for reducing them are different since the properties of air and solids are very different.

Vibration reducing materials like Sorbothane (or Dynamat Xtreme) are much denser than sound absorbing materials like Sonex or fiberglass.

Open cell foam and fiberglass act as tiny baffles for sound, creating friction as the sound waves try to pass through it. The friction/turbulence reduces the sound by converting it to tiny amounts of heat.

Closed cell foam blocks some sound from passing through, but a straight sheet of it would also mostly reflect it back toward the source (like a mirror reflects light). Wedge-shaped pieces of relatively solid materials (including closed cell foam, plastic, rigid fiberglass, etc.) will diffuse sound. Diffusion doesn't reduce sound, but makes it less directional. If the wedges are made of a sound absorbing material like open, rigid fiberglass, then it will reduce and diffuse sound.

Vibration reducing materials like Sorbothane or Dynamat Xtreme also convert vibrations to tiny amounts of heat, but they do it for a solid material which has a much higher speed of sound, etc.

Sound absorption inside a computer cases probably isn't too practical due to the small dimensions relative to the wavelengths of sound.

Sound blocking may be practical if it prevents things like side panels from picking up vibrations, but it won't reduce the sound inside the case much at all. However if it prevents some panel vibration, then it may make the noise you hear from the case quieter.

Vibration damping of case panels does work and is used by things like the Antec cases or by putting Dynamat Xtreme on the case panels.

I use vibration damping on case panels, and for fan mounts. The soft Silicone grommets Antec uses for hard drive mounts are highly effective at preventing hard disk vibration from getting to the case, compared to screwing them directly to the case.

jhhoffma
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Post by jhhoffma » Tue Apr 01, 2008 6:17 am

jeffc,

Good explanation. Just remember that using mass-loading, or "vibration damping" as you call it, also converts sound energy into heat, though not much heat. That energy has got to go somewhere.

Diffusion will in fact reduce sound energy, as some will always be absorbed by the diffusion element (otherwise it would be a true reflection), but you're correct that the greatest benefit comes from reducing the directionality or cohesiveness of the sound.

And I will point out that there are two methods for dealing with vibration: mass-loading and isolation. Using heavy materials to add mass to the case panels is obviously called mass-loading. I explained how this works above. Using grommets or gaskets or other materials to decouple the vibrational source from another object is called isolation. Both are different methods with different uses for dealing with the same problem.

jeffc
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Post by jeffc » Tue Apr 01, 2008 7:24 am

Good point about isolation being another way to reduce noise. That's what the soft hard drive grommets do, for example.

Mass loading is one thing that something like Dynamat Xtreme does, but it also dampens out the actual vibrations by being highly viscous. It's almost like a really sticky liquid. You could also mass dampen with lead or copper sheets, but they wouldn't have the same internal damping as the sticky stuff.

Mass damping works by requiring more energy to create the same vibration. Or said another way, for a given energy input, the heavier mass will vibrate (move) less. E=mv^2.

lor77
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Post by lor77 » Tue Apr 01, 2008 9:00 am

Diffusion will in fact reduce sound energy, as some will always be absorbed by the diffusion element (otherwise it would be a true reflection), but you're correct that the greatest benefit comes from reducing the directionality or cohesiveness of the sound.
And again using which type of foam will reduce directionality or cohesiveness in a higher extend ?
And is this applicable to our pc cases in real life?

jhhoffma
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Post by jhhoffma » Tue Apr 01, 2008 9:46 am

Open cell foam will diffuse the sound the most. To look at it more simply, the more irregular the surface, the more diffuse the reflection. But remember, this type of sound reductions only works well for high frequency (low wavelength) sounds. Low frequency vibrations really won't be affected much, and you will need to resort to the other methods mentioned to reduce it.

That being said, dampening is a stopgap. The easiest and most effective method of reducing noise in a case is to choose components that do not generate it in the first place!

lor77
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Post by lor77 » Tue Apr 01, 2008 10:57 am

Thanks for the throughout explanation about dampening.

I think most people that want to squeeze every little decibel reduction and want to know more about the theory for applying sound reducing materials rather than just applying it need to read this thread.

In my case the only think is left to do is applying the foam and getting an SSD for my primary drive.

jeffc
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Post by jeffc » Tue Apr 01, 2008 9:17 pm

High frequencies have short wavelengths. That's why they're more likely to be affected by short dimensions of sound damping stuff inside a case.

For reducing hard drive noise, start with the quietest drives possible. The Seagate Barracuda 7200 RPMs are pretty quiet. Mike Chin is saying some 2.5 inch laptop drives may be quieter. Also be sure to use the Antec Silicone hard drive mounts that came with your P180. Those reduce hard drive vibration transmission to the case very much.

jhhoffma
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Post by jhhoffma » Wed Apr 02, 2008 6:31 am

jeffc wrote:Also be sure to use the Antec Silicone hard drive mounts that came with your P180. Those reduce hard drive vibration transmission to the case very much.
Eh, they can, but I recommend using them only if you're going to be moving the case around a lot. Otherwise, I'd recommend other forms of soft-mounting like elastic suspension, sorbothane, or other foam. See the Silent Storage forum for the gallery of suspension ideas.

lor77
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Post by lor77 » Wed Apr 02, 2008 7:16 am

As it is written in my signature i use 2 of the most quite 3.5 drives out there the WD10EACS and the SamsungHD501LJ enclosed in 2 Scythe Quite Drives sitting one on top of the other separated by 5cm long silicon mounts(so that some air is flows between them) located both in the lower compartment of the P180.
So i guess i cant do anything to make them more quite.
I was thinking about suspending them but firstly there isnt much space and secondly i dont think i will earn anything since both are sitting inside the boxes.
Suspending them will lower mostly their seek noise something that both drives are missing(they have all most zero seek noise),and will not do anything about general mechanical drive sound,something that the boxes do.

jeffc
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Post by jeffc » Thu Apr 03, 2008 6:26 am

jhhoffma wrote:Eh, they can, but I recommend using them only if you're going to be moving the case around a lot. Otherwise, I'd recommend other forms of soft-mounting like elastic suspension, sorbothane, or other foam. See the Silent Storage forum for the gallery of suspension ideas.
I tried Sorbothane and it didn't work as well as the Silicone. I used the Sorbothane correctly by not having any bracket metal in contact with the screw and clamping down on the Sorbothane moderately tightly.

The O-Ring/rubber-band/mini-bungee cord mounts may be even quieter than the Silicone, but I can't handle the idea of the hard drives slipping out and falling down if I tilt the case the wrong way. So I used the Silicone grommets. They're a lot more secure and very quiet.

jhhoffma
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Post by jhhoffma » Thu Apr 03, 2008 8:34 am

Well, I would say the correct way to use sorbothane is to set the drive on four small blocks (1 in each corner) and not use any mounting. But that would limit the amount of movement you can do.

However, my HTPC has 1 3.5mm WD5000KS on sorbothane blocks on a custom platform and I have to peel that thing off. When the HDD gets warm the Sorbothane softens and gets tackier and sticks to the drive.

I'll post a pic of my suspension method when I get home if I can remember so you see how stable suspension can be.

jhhoffma
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Post by jhhoffma » Thu Apr 03, 2008 5:37 pm

Pic as promised. What is not in this pic is a couple zipties I had to use to pull the floppy drive tray up so that the bungees don't bend it down.

Image

FYI, that ugly green foam is gone and replaced with black headliner fabric, which is adhered to self-adhesive vinyl floor tiles.

Image

The drives are very well isolated, but the bungees are tight enough too keep them from swinging any which way. In fact, I tried shaking the case to see if they would hit the case. They don't.

jeffc
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Post by jeffc » Thu Apr 03, 2008 11:56 pm

jhhoffma wrote:Well, I would say the correct way to use sorbothane is to set the drive on four small blocks (1 in each corner) and not use any mounting. But that would limit the amount of movement you can do.
You may want to check the specifications on Sorbothane. It's supposed to be clamped (compressed) to be effective.

It's possible to put screws through Sorbothane just like the Silicone drive grommets so the screws go into the drive, but not directly into the metal mount. In other words, the Sorbothane is used exactly like the Silicone, but with more clamping pressure on the Sorbothane.

jhhoffma
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Post by jhhoffma » Fri Apr 04, 2008 4:40 am

jeffc wrote:You may want to check the specifications on Sorbothane. It's supposed to be clamped (compressed) to be effective.
There's how something's supposed to work and then there's how it actually works. :P

I know how it's usually used, as we use it at my place of work for isolating instrumentation against motor vibration. However, Sorbothane does not require high compression to be effective. Besides, the most effective Sorbothane for reducing drive vibrations is the 40 durometer stuff, which is really soft and compresses under the weight of the drive over time.

Remember the main idea of using sorbothane or foam is to completely decouple (or as near to complete as possible) the drive from the case to prevent transmission of vibrations. If you still have a hard link (screw or bolt) between the two, you still have a much higher potential for transmission of vibration, which is why the silencing materials that use hard mounting almost never work and people around here use other methods.

jeffc
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Post by jeffc » Fri Apr 04, 2008 7:26 am

The stock Antec Silicone grommet hard drive mounts are very effective and do put a screw through the grommet. But the screw only touches the drive. Only Silicone touches the case. So there is decoupling thanks to the Silicone.

The amount of compression Sorbothane is meant to be used with is in the specifications. It's not very much compression, really very little, but is is some.

You're probably right that the softer Sorbothane is more appropriate for PC use. The vibrations are tiny, not like a submarine motor.

jhhoffma
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Post by jhhoffma » Sun Apr 06, 2008 7:51 pm

I've tried the Antec grommets, and while they're better than nothing, they aren't very effective. At least in comparison to other true soft-mounting options.

But if you have a drive that doesn't vibrate much to begin with then they might be enough.

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