I searched through the articles, reviews, and forums of this site and a few others hoping to find a "roundup" of sound dampening/deadening materials but couldn't find one. I only saw the single "Brown Bread" review.

I'm building a HTPC from a Dign case (http://www.moddin.net/review.asp?ReviewID=45) and I want to make the think as quiet as possible. I'm going to use the quietest components I can find and afford -- I may even decide to go for that $300 fanless PSU from Germany...
And, I'm going to use sound dampening material on the bottom, front and back of the case. So, I does anyone have recommendations for the best sound dampening materials?

I haven't tested this extensively yet, but I've had some success with using a cut up yoga mat. I have an Antec SX1040 with yoga mat material behind the front drive door and it dampens the CD/DVD noise by a lot (attenuates the high frequecies by 6dB or more, lower freq's less so). It's a cheap mod - the cheapest one I've seen is $30 CDN for a 2' x 5.5' piece. Is this cheap compared to Dynamat and the like?

Okay I applied the akasa pax mate to my already quiet pc (4X21dba fans) and I couldn't tell the difference, I guess those sound dampening material is best used for really loud stuff

In a computer noise research project I did a couple years ago, I found that adding sound-deadening material in most cases had very little effect on noise levels outside of the case, and for some frequency bands, noise outside the case actually increased.

If you're looking for sound deadening material on the cheap, one option is fiberglass ceiling tiles-- they have a high reflective absorption coefficient (95-99%), and they're dirt cheap at places like Home Depot (or for Canadians, places like Revy Home and Garden). I think I bought a few 2 feet by 4 feet panels for about $5.

Check out this link: http://mtrs.org/MTRS/noisecontrol.html

I used Automotive sound deading foam for my setup, it's called something like closed cell foam or the like, very light and very easy to use.
The car audio guys use it for stopping road noise coming into the car, cheap as well

Watch out for what sound deading stuff you buy. Dynamat, for example, dissipates the absorbed sound through heat.

All sound absorbing materials dissipate the sound in the form of heat.


Its the First Law of Thermodynamics in action.
The energy has to go somewhere.

But don't worry, the amount of heat we're talking about here isn't enough to raise the temps of your system by even .1C. And half of that is radiated out the backside of the material anyway, and onto the case itself

quote="Rusty075"]All sound absorbing materials dissipate the sound in the form of heat.
Its the First Law of Thermodynamics in action.
The energy has to go somewhere.
[/quote]
Right.
But Dynamat is dissipating sound that would otherwise resonate the case wall (or other piece of sheet metal) and then re-radiate as noise.
The foam (or ceiling tile) absorbs sound waves directly (by providing air friction). It only works for high pitched sounds because of the way the sound waves convert from pressure to motion depending on how far they are from a reflective surface - the conversion is dependent on the length of the wavelength - and the foam/tile isn't very thick so it isn't going to catch much low frequency energy as motion.
I'm afraid I'm not explaining this well (need a white-board) - have a look at F. Alton Everest's books for a good explanation with diagrams.
Anyway, I *have* had good luck attenuating high pitched disk noise by linking a case with automotive sound-deadening *foam* - but it was at least 3/4" thick. I'm not sure PaxMate (which is more like 1/4" thick) is going to attenuate noise low enough frequency to *hear*. Might make your dog happier, though...

I used black automotive undercoating and adhered old mouse mats (the soft rubber ones) to the insides of my Antec SX630 Case. I think it prevented some noise, but mostly, my efforts concentrated on reducing cpu fan noise. I've tried (in chronological order) the volcano III, thermal engine, Volcano 6, thermal engine with the volcano fan, Dr.Thermal V77N, Volcano 9, and now, I've finally settled on the Dr.Thermal V77N with the fan running at 5V. It is by far the quietest of all the HSFs i've tried, even beating out the volcano 9 at medium speed! I agree that the case does not play a huge role in reducing the noise....you gotta reduce noise from its source.
With my case exhaust fan running at 5V and a thermally controlled Antec 303 PSU...it's pretty quiet. Next project...Seagate BV drives.

Sound dampening helps less then you would think. I use simple car noise dampening foam, it's cheap.

You must be prepared to do other stuff before you dampen with noise dampening materials. You need to suspend the HDD's from the case for a start, and preferable also suspend the CPU fan somehow, or the noise will just wander out in the case and you will not get much of an effect from the dampening materials.
Although, some dampening mats will make the case heavier and thus dampen the noise.

I had 12kg (25 lbs) bricks and a wet towel on my old computer. It helped a lot (really!). =^.^=

i think the negative feedback in sound dampening comes from vibration. low frequencies will travel through anything which make them difficult to dampen (or try concrete!). dampening is effective for higher frequency fan noise and hard drive whine especially.
I use akasa mats, but pretty much any sort of firm, dense but soft material will work. a yoga mat is a good suggestion, as well as one of those roll up sleeping mats at outdoor stores.
overall i see no negative reasons for sound dampening your box, just maybe not as many positives as we hope there would be because different materials are only good for absorbing a certain frequency range.

About those black automotive undercoating.

Since the product is intended to be used outside of the cars, can it contain some poisonous substances? Since the materials used to seal and protect the bottom of the chassis often is I think this question is justified. What happens to these kind of stuff when they get heated, approx 30-40 degrees Celsius, and contained in a under-ventilated, small room? I have often thought about using this plates as they are very efficient in canceling out vibrations.

Pape