Thanks to the info here, my new gaming build is up a running and is much quieter than my old C2D setup.

I'm using a ps07 case and it is a little thin so more sound than I would like is still getting out. It's mostly airborne sound but it could use some dampening as well. I'm planning to get some damping material and I started to look at various foams. I inevitably ran across the threads referencing McMaster Carr. Most of the threads were from 2003-05 when McMaster would sell single tiles for about 5 bucks. Now, you can only buy packs of 8 and with shipping it is over $100! Item 9216T1 At that price, prepackaged alternatives make a lot more sense (assuming they work).

I haven't seen any more recent posts about them so I'm curious if they are now obsolete. Does anyone still use them? Anyone know where to buy smaller quantities? Are options like acoustipack a better choice?

If these are still worth while, anybody interested in a local group buy? I'm in the East Bay Area, CA so hopefully there are some SPCR guys in the area.

Judging by what I know of sound physics (which isn't all that much, alas), I suspect you'll see better results from mass-loaded vinyl or the like. You might want to try pasting on a few adhesive-backed, vinyl floor tiles from Home Depot/Lowes/whatever. They're dirt cheap, have been recommended by others on this board, and I doubt more expensive materials will give you appreciably better results.

Hm... I might try the self adhesive vinyl tiles. The top P280 panel rattles like crazy. Was about to buy some Dynamat, but that stuff is expensive, if simple vinyl tiles can do the job for fraction of the price I'm not going to complain

If it's vibration/coupled noise, then adding weight to panels can reduce the coupling. Cheap, heavy floor tiles could do the trick. If it's airborne noise, then thick foam-like stuff is needed to dampen it.

I'm going to be building my new rig in P280. I have to get new front panel from Antec because it's been damaged in shipping and I only found out now. However, I poked around otherwise, and the top panel of P280 rattles if you flick it with you finger. That can't be good, so I want to take pre-emptive steps to silence it. I'm really disappointed at how the quality has gone down though. P18x had solid 5mm plastic top and side panels. P280 feels cheap in comparison. And my case has the same side panel catches defect that was described in the SPCR review. Not a big deal since I can bed them back in shape, but it's just sad to see Antec cheapening out on an otherwise great case.

Sound waves are funky - They tend to bounce, reflect, and wrap around surfaces and obstacles. If you're trying to block sound, you need to block off every crack/vent/etc between the computer and the listening position. Even then, you have to worry about sound reflecting out of the other openings then bouncing towards your ears. The real world application to this is simply to make sure you cannot "see" any fans or vents from your computer case from your sitting position. Cases with doors like the p182 are good for this, but you trade off a bit for cooling, so you may have to end up turning up the fans to compensate for this. Sometimes, having a very efficient and open case (Antec Three Hundred) with very quiet fans is better than an inefficient case with faster fans. Another approach to this is using a heavy material to block the sound waves. This is done in movie theaters with mass loaded vinyl (1 pound per square foot), which is then hung free air between the walls of adjoining theaters. Sound waves will hit the material, which is so heavy, does nothing, and does a combination of reflecting, blocking, and absorbing the sound wave.

If you're going to try and absorb sound, you need to have absorption material that is thick relative to the wavelength. The higher the frequency, the shorter the wavelength. Lower frequency wavelengths can approach inches or feet in length, making absorption within a computer case basically impossible. The mid/lower frequency sound will go straight through whatever you're using to try to absorb the sound. Unless you have a weird high frequency problem (squealing coils, or dying hard drive), adding foam isn't going to help you at all.

Another type of sound management is deadening (mass loading). This is what Dynamat does - it doesn't block or absorb sound. Simply put, this method makes it much harder for a solid to vibrate by making it heavier. This is really easy to test if you'll benefit from this. Simply press down on any portion of your computer that you think may be vibrating and transmitting sound to the air. Sides of cases are a huge culprit, drive cages, etc. If pressing these parts makes an audible difference in the sound, slap something heavy and sticky on it. Dynamat, sticky roofing material, vinyl floor tiles, etc are all fair game. Just make sure that the mass load, and the vibrating solid have a good connection via adhesive, glue, etc.

Hope this helps - I've done a lot of work with sound treatments in cars so I have some good experience with this topic.

Technically, in that case the term is "absorb," not "damp," and the <1"-thick, polymer foams they sell for case "damping" only absorb very high frequencies. They might change noise character, but they'll barely touch the overall volume, even with indirect noise paths giving the stuff multiple absorbing passes.

I have some knowledge about sounds behaviour on a bigger scale (buildings) but i think it's apliciable on this smaller scale just aswell but because of the scale diference i might make some errors so correct me if i'm wrong. Aswell excuse me if there are any language errors because im from the netherlands.

Sound moves in all directions from any point where there is a sound level (amount of dB), as it spreads over a larger area when moving away from the source the sound presure on any point of that larger area is lower then when youre closer to the source. so it can move around corners however if it has to move around corners the amount of sound does get lower because the sound traveled a longer path and is spread over a larger area.
you can block sounds with a barier, meaning in this case the case pannels. the panels will reflect part of the sound, let part of the sound trough to the other side and absorb part because the panel moves while being fixed at the seems. the more flexibel and/or havier the panel the more sound it absorbs. such a panel would absorb lower frequencies better because it is easier to move the panel back and forth slow then it is to move it fast. Things like absorbtion foam is easier to move back and forth fast by sound and therefor it absorbes higher frequencies better while adding to the weight of the panels without making it less flexibel. There are also absorbtion panels for lower frequencies however they are often bigger and heavier, for example in building they often use wooden panels with holes which sizes depend on the frequensies with rockwool behind them. it would reflect the lowest of frequensies, let the specific frequensies it is designed for trough the wholes so they can bounce behind the panel. but still reflect a large portion of the higher frequencies with the area around the wholes and they also can escape easier from behind the panel because they can pass trough the holes easier.

Everything absorbs sound, howerver there is a big diference between how much sound and what frequencies between diferent materials and construction.
the absorbtion is important because if every surface inside the case would reflect everything it just increases the sound level inside the case, but somehow it will always find some way out.

as for the movement of sound, even a panel full of holes help, but it would let the relatively higher frequensies trough better as lower frequensies as lower frequensies have trouble to move trough relatively smaller holes.

so if you hear higher frequensies outside the case the best solution often is to place sound absorbtion for those high frequencies inside the case. (absorbed sound doesn't move out the case but the energy became, a small amount of, heat)
if the sound you here is more the lower frequencies the best solution often is to make the panels heavier but keeping them as flexibel as posible. or in few situation make the size of wholes smaller, a smaller but relatively heavy and flexible mesh in front of fans might actualy help to keep sound in and give it time to be absorbed inside the case.