substitute for Acoustipack foam?

Enclosures and acoustic damping to help quiet them.

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serfurj
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substitute for Acoustipack foam?

Post by serfurj » Wed Mar 16, 2005 7:07 pm

i think mounting foam in my case would reduce the whining noise that the hard drives make, but i'm not willing to dish out $90 on a couple pieces of foam. does anybody know if there is commonly available foam (packaging material?) of the correct density to use as a substitute for Acoustipack?

Tibors
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Post by Tibors » Wed Mar 16, 2005 7:41 pm

Guy's I know you are hiding out there. Don't let me answer all serfurj's questions.

Some discussion about Acoustipack alternatives in this thread:
To dampen or not to dampen.

m0002a
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Post by m0002a » Wed Mar 16, 2005 9:06 pm

One thing to consider when looking at alternatives is that the AcoustiPack is a two layer material. The bottom layer is very, very dense and relatively thin, and the top layer is much thicker that is not at all dense that is supposed to absorb the sound. My own observation (having purchased AcoustiPack) is the top layer is of dubious efficacy and that the thin but very dense layer does almost all of the work of keeping the case quiet.

I developed a hard drive suspension system for a Sonata and also an old PIII Gateway and used a high density closed cell foam for that purpose (although it is not as dense as the first layer of AcoustiPack). I also applied some of the same foam to the walls of the Gateway to quiet the case, and it worked very well, surpassing my expectations. The material has to glued in small pieces but is fairly cheap. It doesn't look that great, but it does work well.

Here is the link where the foam (Wall Plate Insulating Gasket) is described and where you can purchase it.
http://forums.silentpcreview.com/viewtopic.php?t=10450

Just one piece of advice for sound deadening of a case, and for drive isolation: Use a high density foam, preferably closed cell. And make sure it is has the proper fire and electrical rating to be put inside a case.

MonsterMac
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Post by MonsterMac » Wed Mar 16, 2005 10:06 pm

I've had great experiences with paxmate blocking high frequency noise.
Antec P180, 3200+ Venice, Gigabyte A8N Ultra-9, 1gb RAM (2x512) PQi Turbo, eVGA 6600GT w/ NVSilencer, Audigy2ZS, XP-120, S12 430W PSU, 1.2TiB HDD Space

Tibors
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Post by Tibors » Thu Mar 17, 2005 8:29 am

m0002a wrote:Just one piece of advice for sound deadening of a case, and for drive isolation: Use a high density foam, preferably closed cell.
Do you have any scientific reasoning for this? Apart from your own experience described above.

Most commercial sound insulation products (not just those for use inside a PC) use medium density open or half-open cell foam for the absorbtion layer. They back this up with something that is a far better soundblocker than high density closed cell foam.

m0002a
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Post by m0002a » Thu Mar 17, 2005 9:20 am

Tibors wrote:
m0002a wrote:Just one piece of advice for sound deadening of a case, and for drive isolation: Use a high density foam, preferably closed cell.
Do you have any scientific reasoning for this? Apart from your own experience described above.

Most commercial sound insulation products (not just those for use inside a PC) use medium density open or half-open cell foam for the absorbtion layer. They back this up with something that is a far better soundblocker than high density closed cell foam.
I would completely agree with that if a two-piece material is used. But if only one material is used (most likely if one is trying to do this cheaply), I think it is important to keep the sound off the metal walls of the case.

Even closed cell foam has some sound absorption properties. After all, the stuff is not made of steel, and some of the sound passes through the cells is “effectively” trapped inside (I realize that trapped is probably not right word, but I don’t want to get into a scientific discussion of acoustics).

But even if high density closed cell foam did bounce the sound around, as long as it bounces around inside the case, it will eventually attenuate (decrease) to inaudible levels. This is different than when acoustic foam is used in an open air studio, where as much sound as possible “must be” absorbed the first time it hits the foam, so as to prevent reverberations in the studio or listening area.

But we are not inside our computer cases, so letting the sound bounce around a bit more is no big problem, so long as the sound does not transmit directly through the metal case wall, or some other means. The sound will eventually attenuate with all the bouncing around the inside of the case, in a similar manner that sound attenuates when bouncing around inside a half-open cell foam.

serfurj
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Post by serfurj » Thu Mar 17, 2005 2:37 pm

thanks for the replies. i'm thinking about taking this person's advice (using common foam from home depot with paxmate glued on top). if that doesn't work out, i'll try the wall plate insulating gasket.

i'm definitely going to give paxmate a try, despite this review's dismissing it as no good (based on theory alone).

Tephras
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Post by Tephras » Thu Mar 17, 2005 3:37 pm

m0002a wrote:But we are not inside our computer cases, so letting the sound bounce around a bit more is no big problem, so long as the sound does not transmit directly through the metal case wall, or some other means.
That is, however, often what happens - sound escaping through openings in the case. So, the use of an absorber layer, maybe with a sculptured surface, would be more efficient, at least in theory.

m0002a
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Post by m0002a » Thu Mar 17, 2005 4:34 pm

Tephras wrote:That is, however, often what happens - sound escaping through openings in the case. So, the use of an absorber layer, maybe with a sculptured surface, would be more efficient, at least in theory.
You are correct. But when is enough, really enough? (I probably should not ask that question on this forum.)

Krispy
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Post by Krispy » Fri Mar 18, 2005 5:48 am

Like MonsterMac I've had pretty good results with 2 layers of PaxMate. I then covered this with a 2mm layer of open cell foam mounted with 3M spraymount.

2 years on & it's still all attached as well as day one!
[size=84][color=darkblue]Asus A7N8X Dlx | Athlon XP 2200+ | Volcano 12/Nexus 92 fan | 2x60Gb WDJB's | 2x512Mb | ATI Radeon 9200 Pro | Fortron FSP300-60PN | Insulated Case.[/color][/size]

serfurj
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Post by serfurj » Fri Mar 18, 2005 6:41 am

krispy,

where did you get the 2mm open cell foam?

m0002a
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Post by m0002a » Fri Mar 18, 2005 9:14 am

Keep in mind that the best acoustic foam is not open cell. They use an open/closed cell hybrid. This is what "traps" the sound inside the foam. The sound gets in, but can’t get out.

An open cell foam is not much of a sound barrier, nor much of a sound attenuator. It is hard to imagine that 2mm of open cell foam will do much to reduce the sound.

Krispy
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Post by Krispy » Sat Mar 19, 2005 11:48 am

m0002a in reality you are probably quite right about this thin open cell foam. In theory an optomist would hope it might have some microscopic effect.

The reason I fitted it was because it was plastic foil backed & I have a bit of a dust problem. The dust was starting to stick to the black Paxmate. I stuck on the thin stuff, plastic foil side up, so now the inside of the case can be wiped out clean in seconds.

Initially, this may sound over the the top, but in practice it means I don't have to risk damaging anything by the vacuum cleaner nozzle & I have saved a lot of time since. No more memory dimms up the vac tube either! :)
[size=84][color=darkblue]Asus A7N8X Dlx | Athlon XP 2200+ | Volcano 12/Nexus 92 fan | 2x60Gb WDJB's | 2x512Mb | ATI Radeon 9200 Pro | Fortron FSP300-60PN | Insulated Case.[/color][/size]

slimeballzz
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Post by slimeballzz » Sat Mar 19, 2005 2:31 pm

m0002a wrote:Keep in mind that the best acoustic foam is not open cell. They use an open/closed cell hybrid. This is what "traps" the sound inside the foam. The sound gets in, but can’t get out.

An open cell foam is not much of a sound barrier, nor much of a sound attenuator. It is hard to imagine that 2mm of open cell foam will do much to reduce the sound.
When you say "open/closed cell hybrid", does that mean the open/closed cells are blended in together? Or are they two seperate layers on top of eachother?

If the opened/closed cells are mixed with eachother where can I find this type of foam??

m0002a
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Post by m0002a » Sat Mar 19, 2005 9:10 pm

slimeballzz wrote:When you say "open/closed cell hybrid", does that mean the open/closed cells are blended in together? Or are they two seperate layers on top of eachother?

If the opened/closed cells are mixed with eachother where can I find this type of foam??
Acoustipack has 2 layers:

A 5mm "semi-open cell foam" that is used for the top layer of their product.

The bottom layer is a 2mm "very high density acoustic barrier mass".

http://www.acoustiproducts.com/en/materials.asp

Tom Brown
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Post by Tom Brown » Sun Mar 20, 2005 9:19 am

m0002a wrote:One thing to consider when looking at alternatives is that the AcoustiPack is a two layer material. The bottom layer is very, very dense and relatively thin, and the top layer is much thicker that is not at all dense that is supposed to absorb the sound. My own observation (having purchased AcoustiPack) is the top layer is of dubious efficacy and that the thin but very dense layer does almost all of the work of keeping the case quiet.
I tried acoustipack, blackhole 5, and some fairly dense foam I got at a surplus store that has a thin layer of closed cell foam on one side.

It's hard to say which did the best. I think it was the blackhole 5 but I hesitate to make this claim because I don't feel I had enough controls. I certainly didn't take any measurements.

The $7 foam I picked up at a surplus store was intended as automotive sound deadening material. It worked reasonably well. I just glued it in with weather strip adhesive.

The acoustipack was less dense than the cheap foam and seemed to work about as well. I wanted to see how it differed from the other things I tried and it didn't seem to differ much. At least, I couldn't tell the difference.

The main problem with blackhole 5 is that it's even more expensive than acoustipack. It is used as dampening material in loudspeaker construction. Neither the acoustipack or blackhole 5 are worth the money, IMO.

Again, I didn't take any measurements, I performed this on three different Sonatas (all with stock fans and L1A modded PSUs), but I didn't compare all three mods side by side to a stock Sonata.
Modded Antec Sonata

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