AcoustiProducts Vibration Dampers

FAN MOUNT TESTING

Let me first anticipate a question that many regular SPCR readers will ask:

Q: Why are there no acoustic measurements or audio recording of these vibration damping devices? These are great tools that help make SPCR reviews so useful and informative!

A: Unfortunately, there are limits for any sound level meter or audio recording system. In this case, neither provide any further insight into the products being tested beyond descriptive narrative alone. In fact, the measurements and recordings serve to obfuscate the effects of the damping, which are subtle in many cases and more qualitative than quantitative. SPL readings are virtually useless, as there is almost no measurable difference. The sound recordings could be useful but only if you had a really high quality audio playback system. Most people don't, and even if you did, it would still be tough to hear.

So, having dealt with that...

The fan gaskets and fan mounts were tested in two ways. First, an 80mm Zalman fan (PS80252H) was installed in a generic steel case using conventional screws to establish a noise baseline. Then, each mounting system was tried in turn, and the subjective differences recorded. The fan was run at 12V and 5V for each test. No measurements or recordings were made, as the differences were too small to be measurable. At this stage in a silencing project, a subjective improvement in the quality of noise tends to matter more (and are easier to achieve) than a reduction in the amount of noise.

The case has been heavily modified for use in other projects. It was a cheap generic case that was always kind of flimsy, and all the cutting and hacking has not helped. It's pretty susceptible to picking up and amplifying vibration. The case was chosen in hopes that any differences in vibration noise would be amplified.

Fan grills were cut out of the test case, and an additional hole for a 92mm fan was drilled in the top.

Each mounting system was also tried in an actual system — my main system, whose noise signature I am intimately familiar with. The acoustic details of the system are as follows:

• Seasonic Super Tornado 300W, with the fan controller bypassed and the stock fan undervolted to 5V
• Antec Sonata Case, with stock exhaust fan undervolted to 5V and soft-mounted with the stock Antec fan mounts
• Zalman FB165 PCI Fan mount with Nexus Real Quiet 80mm fan, undervolted to ~6V (inaudible) using a Zalman Fanmate 2
• Scythe FCS-50 heatsink with Panaflo FBA08A12L1A 80mm fan, undervolted to 5V
• Samsung SP0802N 80 GB hard drive, suspended with elastic cord
• Samsung SP1614N 160 GB hard drive, suspended with elastic cord

The mounting systems replaced the stock Antec fan mounts that decoupled the stock exhaust fan from the case. The noise baseline for this test quite challenging because the fan is already soft-mounted. It may be that the overall noise will increase if the fan mounts cannot match the performance of Antec's stock fan mounts. On the other hand, any improvement in noise levels will be doubly impressive.

AcoustiProducts' fan mounts were compared against the stock fan mounts that come with the Antec Sonata case.

Test 1: Zalman 80mm fan + Empty Steel Case

The 80mm Zalman fan is hopelessly loud at 12V. The huge amount of direct acoustic noise it produces drowns out any vibration noise. Although vibration may be reduced with both mounting systems, the reduction is inaudible because the primary source of noise is not vibration.

Because of this, the tests were repeated with the fan undervolted to a more reasonable 5V. At this level, the noise it produces is primarily a low frequency buzz that is muffled slightly by an equally low frequency motor hum. Airflow noise is minimal, although it would probably become more of a factor when impeded by a fan grill. This fan would not be a good choice in a quiet system, but for the purposes of listening for changes in vibration-induced noise it is perfect.

Anti-Vibration Fan Gasket AFG80B

With the fan gasket installed, the fan's buzz was slightly muted. The difference was most noticeable from the front and sides of the case, and disappeared entirely behind the case where there was a direct path between the fan and my ears. The difference in noise quality was very small, but it was enough to swap the roles of the buzz and hum: Instead of the buzz being muffled by the motor hum, I would characterize the noise as motor hum disrupted by a low buzz.

Anti-Vibration Fan Mount AFM02B / AFM03B

Both the retail and OEM mounts were tested, but they sounded the same so I will describe them together.

These fan mounts were more effective than the fan gasket, and the difference was audible from all angles rather than just in front of the case. As with the fan gasket, only the buzz in the noise signature was affected — the motor hum stayed the same. In fact, the buzz disappeared almost entirely, changing from the dominant source of noise to a background rattle that was only audible within a foot or two of the case. The motor hum was still present as a pure tone around 200 - 300 Hz, but most of the resonant buzz was eliminated. This indicates that the fan mounts were doing their job effectively.

Test 2: In-System Performance

The system sits in a cheap computer desk that amplifies the noise it makes. The character of the noise is predominantly the quiet whoosh of airflow. There is a residual amount of hum, which may be vibration-related — or it may be direct noise from the various fans. The system is usually inaudible because the ambient noise around it tends to be quite high. Only at night when the ambient noise drops does it become audible. All listening tests were done at night when the system was clearly audible.

Anti-Vibration Fan Gasket AFG120B

As far as I could tell, the Fan Gasket had no effect on the noise signature of my system. Neither the airflow noise nor the low hum appeared to be affected by the change in fan mount.

Anti-Vibration Fan Mount AFM02B (Retail)

Only the retail fan mount was tested in my system. The previous test convinced me that I was not going to see a performance difference between the two versions.

My first impression of this mounting system was that it helped — a little bit. The low hum beneath the whoosh of airflow may have been even lower than before. Unfortunately, because the hum was so quiet already, it is hard to say for certain whether or not the improvement is imagined. Now, after the mounts have been in use for a week or more, I am as unsure as ever whether the noise character of the system has changed or not. If there was a change, it wasn't large.

ACOUSTIFEET

AcoustiFeet are designed to isolate a computer case — or any other piece of electronic equipment — from the surface it is placed on. Like the fan damping products above, the idea is to reduce or eliminate the transmission of vibration and thus isolate the noise it creates to the case. This prevents vibration from causing further noise, which might happen if the case is placed on a wooden desk, for example.

Obviously, the best approach would be to isolate the individual sources of vibration inside the case first to prevent the case itself from resonating. However, if vibration is still a source of noise even when the individual sources of vibration cannot be damped any more, a further acoustic benefit may be had by using these soft adhesive feet. AcoustiFeet also have other applications. AcoustiProducts suggests using AcoustiFeet to damp everything from home theater PCs to speaker cabinets. Speakers in particular may benefit from being isolated, as poorly isolated speakers can add unwanted resonances to the sound that they reproduce.

AcoustiFeet come with an adhesive backing, four to a sheet.

In total there are eight different versions of AcoustiFeet: Four different softnesses and each softness comes in either black or semi-transparent silicone. Each softness has a maximum recommended weight it can support, beyond which its vibration-reducing properties are reduced. The maximum weights along with the recommended applications for each are summarized below:

The difference between the different models was apparent to the touch. Feet with lower maximum weight were much softer than higher rated feet. It is not hard to imagine that a heavy case would become quite unstable if used with the softer feet. In fact, this effect could be seen on the custom-built system from Puget Systems that we reviewed not long ago. This system was extremely heavy thanks to the large radiator installed on the side, and equipped as it was with soft feet, it listed noticeably to the left even when placed on a hard surface due to the uneven weight distribution.

Although it is a good idea to pay attention the recommended maximum weights, your choice of feet may be limited by availability. Many web stores only carry the highest rated model — the ACF3007-30B.

The AcoustiFeet were tested on the same system used to test the fan mounts above. The system weighed in at 16 Kg according to my not-legal-for-trade bathroom scale, so the ACF3007-25B with a maximum weight of 22 Kg was used.

Once the existing feet on the Antec Sonata were removed, installation was as simple as peeling the feet off of their backing and applying them to the bottom of the case in appropriate places. The hardest part of the installation was finding a way to remove the existing feet, which were firmly stuck to the bottom and couldn't be pried loose with my fingers alone. Eventually, a paint scraper (otherwise known as a razor on a stick) was used to scrape them from the bottom of the case.

Despite the fact that the stock feet on the Sonata are hard rubber and the position of the system in a cheap computer desk, I heard very little difference with the new feet installed. This is probably because there was so little vibration being transmitted to the case in the first place. The major sources of vibration in the case, the hard drives, are already mechanically decoupled inside the case, so there simply isn't much vibration for the feet to damp. Only the faintest trace of vibration can be felt when holding a hand against the side case panel of the case. AcoustiFeet would be more effective with a system that is less dead than my own.

CONCLUSIONS

AcoustiProducts' vibration-reduction products are meant to address a very specific issue: Vibration-induced noise. A system that is too loud for vibration-induced noise to be heard will not benefit much from these products. Neither will a system that is already well damped — these products cannot damp vibration where there is none to begin with. This explains why so little difference was noted when the products were tested in my existing system: The system already has very little vibration.

In a system where vibration is more of an issue, these products could be what is needed to reduce system noise enough to put it below the ambient noise level. If you are not sure, at less than $10 each, they are cheap enough to experiment with.

Another use for these products may be to compensate for flaws in the system elsewhere. For example, the fan decoupling products are probably more useful in an aluminum case that resonates more easily than a steel case. If a vibration-prone aluminum case cannot be avoided — in a SFF system for example — a thick silicone fan gasket may be invaluable for overcoming the case's acoustic limitations. AcoustiFeet may help compensate for vibration in a system where the hard drives are hard-mounted, because they are often a major source of vibration.

In terms of noise reduction, the new fan mounts seem superior to the fan gaskets. However, the gaskets do one thing that the fan mounts don't: They seal the area around the fan to ensure that air cannot recirculate around the edges of the fan. This seal is also useful for keeping dust from bypassing any filters if the fan is used as an intake.

In sum: None of these products are going to make a night and day difference in most systems, and their noise-reduction effect will vary widely depending on the specifics of the system. Regardless, they are well-designed products that will probably do as good a job in damping vibration as anything similar we've come across. Used judiciously, they can be invaluable for tackling noise problems without resorting to custom modifications. If you suspect vibrarion to be a source of noise in your system, one or more of these products may well be worth a try. It may lead to an audible improvement; it certainly won't hurt the acoustics or the wallet.

* * *

Our thanks to AcoustiProducts for the opportunity to examine these vibration-damping products.

Discuss this article in the SPCR Forums.

Help support this site, buy from one of our affiliate retailers!

Search: All ProductsComputersPhotographyElectronicsSoftwareVideo GamesMoviesMusicBooksToysOfficeJewelry & WatchesApparelHealth & BeautyHome & GardenBabies & KidsFlowers & GourmetSporting GoodsMusical Instruments