The review compares the noise from a AcoustiPack-treated Antec Sonata case versus a “bare” Sonata. Goes on and on… but lots of interesting things in there — other damping materials, what the stuff should do, and high quality MP3s for comparisons. A bonus for the uninitiated: One is of the Panaflo 80L at 12V at 1 ft.

February 11, 2003 — by Mike Chin

Acoustic damping materials are virtually ubiquitous in the modern world. Fiberglass batting, foam, and all manner of specialized materials are used in an incredible range of applications to combat and control noise. In computers, however, it is not yet common. One place many SPCR readers may have seen it is beneath the metal protective cover of the Seagate Barracuda IV hard drive: a bit of blue foam is visible there. This foam helps to keep the Barracuda relatively free of high frequency whine. The fact that this quietest of all hard drives uses damping materials is probably significant. As far as I am aware, no other hard drives incorporate acoustic damping materials.

In my own systems, some damping materials are used — things like heavy carpet underlay and recycled foam from packing materials — but until now, I have never tried any of the aftermarket damping materials sold specifically for computer cases. There is little question that acoustic damping can help reduce noise.

The main question is,

How much money, time, and effort is required with acoustic damping materials to obtain what level of noise reduction in a PC?

Many PC silencers are of the opinion that using the quietest components and reducing the noise of components at their source makes damping materials unnecessary. This was generally my point of view, too. My perspective has been changed with exposure to the product under review.

This article began originally as a comparative review of four brands of damping materials marketed for use in a PC case. All share the common feature of being backed with adhesive on one side so that it is relatively simple to apply. They’re shown in the photo below (clockwise from top left):

• Pax.mate by Akasa — purchased (typically <~US$20)
• Wispermat by Muffled Computing – submitted by Muffled Computing, US$20 online
• ProStudio by CoolerMaster – purchased (typically <~US$20)
• AcoustiPack™ by Acousti Products

Why this article turned into a review of just the one product will become clear as you read on.

TEST METHODOLOGY / PLATFORM

After a great deal of research into the question of how to analyze the effectiveness of these damping materials, I came to the unavoidable conclusion that there is only one practical way:

Apply the damping to a case as recommended by the manufacturer and compare it to an unmodified case of the same type, the same model, with the same noise sources (computer components) in it.

This conclusion took a long time to reach, mainly because it was the one I wanted most to avoid. Why was I so loathe to use this methodology?

Applying the damping looked like a mountain of tedious work, especially without at least one pair of matching cases. My hands were going to take a beating…

Fortunately, Antec came to the rescue by generously sponsoring another Sonata case, this time a pre-production black one to match the earlier beige sample used for the review conducted some weeks ago. This seemed a reasonable case to use as a test platform, as the Sonata is designed specifically as a reduced-noise case. Thank you Antec!

Still this meant applying four and removing at least two sets of the damping materials. Ideally, what I wanted was five identical cases. (Good thing I didn’t get them! As you know the review only focuses on one product.)

NOISE CHALLENGES

Before getting into the product details, it seems worthwhile to consider the challenge noise damping materials face in a PC. Here are some basic observations:

1. The main goal is to reduce noise — all noise. In a typical PC, there are high-pitched whirring noises from hard drives and small high speed fans, the mid/high frequency noise of fan turbulence, the lower frequency rumbling and clacking seek noise from hard drives. While we tend to identify the more annoying high frequency noises quickly, there are noises in every frequency band.

• The damping materials must be effective not in a narrow or limited bandwidth but across the entire audible frequency range.

2. The case is made of thin metal panels and plastics, which do not block, contain or dampen the noise inside well. The metal chassis and panels often vibrate, sometimes subtly, sometimes obviously, adding their own noise to the mix. This noise is usually lower in frequency, but their sympathetic vibrations add to the whole mix of noise.

• The damping materials must reduce or eliminate sympathetic panel resonances that contribute to the noise, and increase the noise blocking/containing capability of the case panels.

3. The case has air vents that allow noise to escape directly and easily. Sound becomes more directional higher in frequency, becoming more like narrow beams of light rather than waves from a splash in a pool (the behavior at lower frequencies). So in theory, it should not be that hard to minimize high pitched whining or whistling by eliminating direct paths to the ears. In practise, as most PC silencers know, high pitched noise is not easily eliminated by baffles alone, most likely because there are many hard and reflective surfaces that noises bounce off to find their way out the openings, regardless of frequency.

• The damping materials must reduce the noise and reflections within the case by absorbing it as much as possible. Coverage of as much internal surface area as possible is likely desirable.

4. Other desirable qualities.

• Nonflammable — Acoustical or soundproofing foam is most often made from polyester, polyurethane, or some other poly-something or other, all of which have a tendency to be at least somewhat flammable.
• Doesn’t smell — Nasty smells have been reported to emanate from damping materials, especially as the computer case heats up. It is not clear whether this smell is accompanied by any toxic outgassing or is simply unpleasant.

PRODUCT COMPARISON

How do the contenders fare on the points under NOISE CHALLENGES?

The Akasa Paxmate is far too light, way too thin and has too low a density to meet any of the criteria set above. Its total area coverage is the only way that it passes — just barely, but it is a minor 1 out of 4. It is simply not worthy of a serious look. It also smells terrible, although one user mentioned it seemed to go away after a few days. It is unlikely that applying this product could have any significant impact on the noise of any PC in any case. Anyone with the least bit of understanding of acoustic damping will come to that conclusion in a 30-second examination. Not recommended.

The Cooler Master Pro-Studio comes in a really nice lime green translucent plastic case with handles and snap locks. It’s the nicest part about this kit. It is too light, too low in density, and covers way too little surface area to have any affect to noise in a PC. If 4 or 5 kits were purchased and their entire contents applied to the interior of a PC case, there would probably be a small decrease in high frequency noise. Not recommended.

As the above profile of the 1″ Wispermat by Muffled Computing shows, this is a composite of 3 materials. The thin grey strip in the center is a dense vinyl layer. The acoustic foam on either side of the vinyl layer is considerably less dense. The thicker outer layers seems stiffer and more coarse, while the inner layer closest to the adhesive seems both softer and finer. Its weight and density is very close to that of the Acousti Products Acoustic Composite sheet (see below). Wispermat is thick enough, dense enough, and heavy enough; alas only one 1/2″ sheet and a 1″ sheet were provided. Not nearly enough to conduct a full review. They were excluded from this roundup only for that reason, and will be the subject of a review in the near future.

ACOUSTIPACK™ DETAILS

AcoustiPack™ Deluxe: 4.6 kg (over 10 albs) of 4 different types materials

Acousti Products, based in the UK, are relatively new to the market. They offer two kits, a standard and a deluxe version, the latter offering more materials, and more types of materials for a larger case. The variety of materials in the deluxe kit indicates an approach that is considerably better thought out and more sophisticated than others. Both kits easily meet all the above criteria.

Referring to the photo above, starting with the materials on top and moving down, the Deluxe AcoustiPack™ contains…

• 1 precut rectangular block of Acoustic Foam for spare 3½ inch drive bays.
• 2 precut rectangular blocks of Acoustic Foam for spare 5¼ inch drive bays.
• 1 Acoustic Foam sheet featuring the AcoustiContour™ anechoic surface
• 2 Acoustic Composite sheets – 12.5mm thickness (2.5mm Acoustic Barrier Mass and 10mm Acoustic Foam)
• 2 Acoustic Barrier Mass sheets – 2.5mm thickness

Each of the 5 sheets measures a substantial 495 x 395mm (19.4″ x 15.5″), which is large enough to cover the entire side cover of almost any tower case. The total weight of the package is substantial, at 4.6 kg (10 lbs).

The Standard AcoustiPack™ has 3 Acoustic Composite sheets (same size as in the Deluxe kit).

Acousti Products’ web site has extensive details about these various materials. It provides the most comprehensive information of all the PC damping materials referred to above. It even includes this graph showing lab measurements of the materials’ damping qualities. All this is impressive, as it suggests a carefully studied approach to development, rather than the typical marketing-driven, me-too approach.

Acoustic Foam — AP use a semi-open cell, polyurethane foam. This is approx. 65 kg/m³ – unusually dense compared to alternative noise-reduction foams. The advantages claimed for high density foam:

• Improves sound absorption efficiency at lower frequencies (sub-1KHz) – said to be critical
• Helps to maintain a low flammability performance, and
• Withstands being manufactured into thin ‘low-reflection’ layers for dual-layer composites

“The acoustic foam is certified UL94, ISO 3582, FMVSS 302 and DIN 4102 for low flammability, and can be operated normally within the temperature range -40°C to +120°C.”

Acoustic Barrier Mass — This quote is from AP:

“Manufactured from a flexible polymeric material incorporating additional mineral fillers to increase mechanical strength, durability and fire resistance. The material is not bitumen-based, and does not give off undesirable odors when warm. This material is very dense at approx. 2000 kg/m³. It is designed to add mass to computer casing, for example, sheet aluminium, steel, alloys and non-glossy plastic surfaces. The material mass acts as an acoustic absorption barrier, significantly reducing noise transmission and reducing any natural resonance frequencies.” It is considerably more effective at sub-1000Hz frequencies than the acoustic foam.

“The acoustic barrier mass is certified to ISO 9772, DIN 75200, ISO 3795 and FMVSS 302 for low flammability, and can be operated normally within the temperature range -25°C to +120°C.”

They recommend combining the Barrier Mass with the Acoustic Foam whenever possible — for example, on the main left side cover. This ensures the best broadband noise reduction. Their Acoustic Composite sheet, which is not described in detail, is a composite of these two materials. The photo below shows the profile of the composite sheet; the thin lighter gray layer is the heavy barrier mass:

Adhesives: Acousti Products use water-based, nonflammable adhesives. They say these are

“less odorous than solvent-based adhesives in some similar products… and can be operated normally within the temperature range -20°C to +150°C. If a mistake is made during the application of acoustic materials, our adhesive allows for the materials to be peeled off and then reapplied.”

A Caution:

“Although the range of operating temperatures stated above are those published by the manufacturers of the raw materials – we strongly recommend that materials are not placed directly against hot components. This is to ensure that products are installed with optimal safety in mind and to help maintain hardware longevity. Always read the printed instructions with each product prior to installation.”

APPLYING THE DAMPING

The biggest challenge to applying the AcoustiPack™ materials to the Antec Sonata is that the right side of the case is not removable. The gap between the motherboard tray and the right side panel is too small for any material to be applied to either, as shown in this photo below, taken from the PSU location looking towards the front of the case.

After careful study of the available spaces and access to various portions of the Sonata case, I decided to use the Deluxe AcoustiPack™. I wanted the flexibility of its wide range of materials.

I consulted Acousti Product’s fitting instructions, included with the kit, as well as these resources on their website: well-illustrated instructions and FAQ recommendations. Here is the approach I decided to take:

• Cover as much of the internal surface area as possible without limiting airflow.
• Apply additional damping around the intake vent, which is closest to the listener when the PC is placed in the typical under-desk location.
• Combine the Barrier Mass with the Acoustic Foam for maximum noise reduction on the removable left side panel.

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1) Antec Sonata case on operating table (dirty floor rug).

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2) Measure twice… cut with sharp utility knife and/or scissors.

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3) Top piece for right side panel.

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4) Between step 3 and this one, there were actually about 3 dozen steps, but you don’t need to see them.

• The composite material was applied on the top, the bottom, and as much of the right side, front and back panels as possible.
• The foam in the center patches of the right panel in the middle of the motherboard tray were simply cut to size to fit those openings. The mounting standoffs keep the bottom of the motherboard from touching the foam. See 1) above as a reference.

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5) Some slightly sloppy cutting for Acoustic Composite material behind the front door. A photo was not taken, but a layer of Acoustic Composite material was similarly applied to the inside of the plastic bezel intake vent.

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6) The right panel with Mass Barrier sheet on bottom and convoluted Acoustic Foam on top.

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The installation process took more than two hours. (It would go faster if you were not stopping to take photos or make notes.) One and a half sheets of the Acoustic Composite sheet, one Acoustic Barrier sheet and almost all of the Acoustic Contour sheet were used. The total weight gain was about 8 pounds.

The adhesive is very sticky, but can be pulled off and reapplied at least once to get the alignment right. (I actually did it a couple of times with a few pieces.) None of the materials smells much. Finally, the 3 foam blocks for drive bays were added. They friction-fit into place easily.

NOISE REDUCTION

The True380S PSU in each Sonata case was used to drive various fans, and do A/B comparisons. It made for a relatively simple series of listening and measuring comparisons.

After trying a number of different fans for noise makers, I concluded that the greatest difference was most easily heard and measured with the loudest noise sources. Rather than present an exhaustive set of data about different noise sources, the loudest, most dramatic one is detailed here.

Both listening and acoustic measurements were conducted in the main test lab, a converted kitchen with no carpeting and very live acoustics. The ambient noise was estimated to be around 20-25 dBA. The cases were placed on the top of a very heavy steel office desk. It did not contribute any resonance noise when the loud fans in the cases were turned on. The Sonata’s PSU is too quiet to contribute to the overall perceived or measured noise in this setup.

Main test instrument: Heath AD-1308 Real Time Acoustic Analyzer / Sound Level Meter. Note: This machine is not calibrated and very old. Its accuracy is somewhat questionable, but above 40 dBA, it seems to jibe with both what I hear and with other more accurate instruments.

The venerable Heath AD-1308: OK above 40 dBA…

Noise maker:

• Thermaltake 70×25 mm fan, FD12702598-2F
• Specifications: 49 CFM, 6000 RPM, 0.55 Amps, 47 dBA

This Thermake fan is the noisiest fan in the lab. It is used on the Thermaltake Volcano 7+ heatsink. Measured noise:

• 10″ distance: 64 dBA — 10″ was chosen because the Heath SLM’s mic could be positioned at about the same distance even when the fan is inside the case.
• 40″ (~1 meter): 49 dBA

While it can be categorized as broadband noise, there is a marked peak of 5-6 dBA at 4-8 KHz, centered at ~6 KHz. It makes quite a screaming racket, with lots of whine and whoosh — wind turbulence noise.

The fan was placed on the bottom center of each case in the frame used to mount it to the Volcano 7+ heatsink. In the undamped case, a thin piece of closed cell foam was used to keep the fan from chattering and vibrating against the metal case floor.

*These distances are ~10″ from the fan — albeit through panels and grills. It is about the same distance as the first free-air measurement above and thus directly comparable to consider the impact of the case.

PRELIMINARY ANALYSIS

The data indicates that an undamped case has a fairly significant noise reduction effect simply by enclosing the noise source. The improvement measured from the front of the case was 9 dBA. The AcoustiPack™-treated Sonata improved on this by a further 7 dBA for a total of 16 dBA noise reduction, which is very dramatic.

Sounds really good? Keep reading; the story does not end here.

• The measurements from the back of the case were not as good. At about the same 10″ distance from the fan, the noise at the case fan exhaust outlet of the undamped Sonata was 63 dBA, just 1 dBA lower than the fan in free air. This difference is too small to be considered significant; you’d have to say the noise level was the same.

• In contrast, the noise at the case fan exhaust outlet of the damped Sonata is 55 dBA, which is louder than measured at the front of the damped case but 9 dBA lower than the fan in free air.

Another listening comparison and measurements were done. This time, the fan vent in the back panel of both cases was blocked completely with some scrap composite Acoustic Composite material. Naturally, there were still many small holes and gaps where some sound could emerge, but now the exhaust fan hole for the PSU became the largest opening on the back panel.

Keep in mind that the above test is completely artificial. In a real system, the exhaust vent could not be sealed without components overheating inside. But it does show dramatically the effect of the noise coming out through that back vent.

MORE ANALYSIS

So what does all this mean?

• The greatest amount of noise emerges from the fan exhaust vents in the back. This probably holds true for most cases, as they generally feature indirect sound paths in the front intake vents and direct outflow vents in the back.

• The overall noise perceived from the case will depend greatly on how close the back of the case is to the user. Also, acoustic damping materials on the wall behind the case could lower the overall noise substantially.

• It is difficult to correlate any of the measured numbers with what I actually heard. The reality is that it’s the total acoustic energy emanating from the case that mostly determines what I heard. This requires a sound power measurement, far beyond the capacity of my test gear.

• A point somewhere between the of the back and front measured noise levels with a slight bias for the higher level might be considered a rough estimate of the perceived noise — 60 dBA for the undamped Sonata and 53 dBA for the damped Sonata. (Acoustics purists will kill me on my methodology but probably not argue too long with the guesstimate numbers.)

• The estimated overall noise reduction of the AcoustiPack™ damping treatment in the Antec Sonata case can be said to be roughly 7 dBA. This correlates reasonably well with what I heard, given my understanding of the dBA scale.

• But in a more damped room — one that has carpeting, thick drapes and plush furniture– the noise level of both cases will be lower, and the difference between them may also drop. Ah these noise complications will drive you crazy! This was precise what I heard when the cases were taken over to Adri’s place for making digital recordings of the cases.

MP3 NOISE SAMPLES

My musician friend Adri has a nifty Sony portable minidisc recorder and a high quality stereo microphone she resorts to when “shooting on location”, so to speak. Adri graciously agreed to help me capture some PC noises with her audio gear for the benefit of SPCR readers. The goal for making these recording was so that you could hear an approximation of the noise that I heard and am discussing and measuring here.

We first listened to the Volcano 7+ fan in the two cases in her living room. Adri marveled at how anyone could stand to have such a noisy fan in their computer. I must have become deafened temporarily; I could only marvel at how much softer the noise was in her carpeted living room compared to the hard live test lab.

After some preliminary listening and testing, Adri determined that a small bathroom on the main floor was the best, most isolated location — equidistant between the distant traffic noise from the north windows and the hum / buzz of her server bank in the upstairs landing. All the recordings were made with the Sony DAT recorder gain at maximum, and the mic positioned about a foot from the fan.

• The recording equipment:
  • Sony portable minidisc recorder MZ-R50
  • Sony stereo electrec condenser microphone ECM-MS907
  • MOTU 828 firewire audio interface

• The 4 recordings of the Volcano fan in the cases were made with the mic placed on a cushion approximate 4″ away from the front or back of each Sonata case, which was placed on the floor.
• Because each recording was made at the same level, if the payback level is not changed as you switch between recordings, you should get a good sense of the relative loudness level of the different setups.
• As a reference, the Volcano fan was recorded by itself from 12″ away — about the same distance between the Volcano fan and the mic when the fan was in the cases.
• Finally, a Panaflo FBA08A12L, SPCR’s reference standard, was also recorded as a reference – at 12″ distance, and 12V.
• The files were transferred to Adri’s mixing computer and converted to .wav files. I then converted the .wav files with Cool Edit 2000 to stereo MP3 files using 96kB sampling. Each recording is 15 seconds long.

WITH LOW NOISE COMPONENTS

Thus far, the testing and analysis has focused on a “system” whose noise level would be considered ridiculously loud by SPCR standards. This was necessary in order to work with easily measurable and recordable levels. But what about with a system whose components have been carefully selected and optimized for low noise?

This question required a third test, of course. There are no measurements offered here, only my listening observations, because the noise level is far too low for the Heath SLM.

Noise makers:

• Panaflo FBA08A12L1A 80mm fan – SPCR’s reference: spec’d at 21 dBA at 12V; 12 dBA at 7V
• Seagate Barracuda IV 40G, in idle – rated at 20-21 dBA sound power (which is usually several dBA higher than typical SPL at 1 meter reading). Mounted normally using the rubber grommeted drive mounts in the Sonata.
• Antec Sonata True 380S PSU – measured to be 42 dBA nearfield. There is no easy way to convert this to a 1 meter reading; I would guesstimate it to be somewhere between 26 and 30 dBA at one meter.

This test was run with the Panaflo at 12V, and then again at 7V. The fan was placed on its side the bottom of the case.

In Test 3, it became clear that with the Panaflo fan at 7V, the PSU became the limiting factor in noise reduction. The damping materials can do little to reduce the noise of the PSU because its noise source, the fan, is located on the back panel, virtually on the outside of the case.

The 12V Panaflo is louder than the PSU fan, but when inside the damped Sonata, gets to about the same volume level. While the damped Sonata with the 7V Panaflo is the quietest, its advantage over the undamped case is not nearly as big as before; much less than the 7 dBA estimated with the loud fan earlier.

CONCLUSIONS

You’re a trooper if you read through all the above to get here. If you did a quick jump and scroll to get here, instead, I don’t blame you. It’s been a long review for me too!.

The Deluxe AcoustiPack™ by Acousti Products represents a thorough and effective approach to dampening materials for computer cases. The variety of damping materials supplied, and the various functions they perform, as well as the comprehensive information for the end-user — all these bespeak of a carefully researched solution not evident in other damping products.

There appears to be two main potential uses for AcoustiPack™.

• Where the lowest possible noise is desired. If there are any fans or noise makers inside the case, AcoustiPack™ damping will make a difference. Obviously, it is easiest to apply when building a system up from the beginning, but it is easy to retrofit as well.

• Where the existing PC setup is considered ideal, and/or no more can be done to reduce the noise of existing components, yet the system is still too noisy. An example is a recording studio where high computing power and stability is desired. The overall noise of the system is too high, but the users do not want to risk any possibility of overheating or instability with things like slowing down noisy fans or replacing noisy hard drives. AcoustiPack™ would be a safer approach.

For SPCR diehards, there are three ways to consider AcoustiPack™:

• Make your system as silent as you can. When it just can’t seem to get any quieter, but you want it to, give AcoustiPack™ a try. It could buy you those extra few decibels of noise reduction, so difficult to achieve once you get below 20 dBA. Just make sure your PSU is not the loudest noise source.

• Start with AcoustiPack™ and you won’t have to work as hard to get the noise down. With its ability to dampen fan noise, you might just let that Panaflo 80L run at 12V (no!) on that huge copper HS so you can even try… (gasp!) overclocking!

• Ah, that damping stuff is for sissies! Real silencers do it by tweaking and fine tuning and undervolting and rubber boxing and modding and soldering… If you resort to damping materials, why, why, that’s just a cheap cop out!

Whether you consider AcoustiPack™ damping a necessity or a luxury really depends on the approach you take to PC quieting, and on your noise standards. Regardless, Acousti Products have clearly come up with a useful tool to add to the PC silencer’s toolbox. Recommended.

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Much thanks to Acousti Products for the review samples, and to Antec for the extra Sonata case for this comparison, and our apologies to Muffled Computing for not being on the ball about obtaining more samples to do a review. And great thanks to my friend Adri for her creative, expert approach to the audio recording challenges.

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As we were “going to press”, word came from Acousti Products that they have nearly finished developing a new pre-cut kit for the Antec Sonata case. They say it should be available soon. Antec may also offer it directly.

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