A well-known noise-damping company offers a variety of vibration damping devices for mounting fans, and similarly soft feet. We take a listen to what AcoustiProduct’s new vibration dampeners can do for PC noise.
August 11, 2005 by Devon
Anti-Vibration Fan Gaskets (80mm, 92mm, 120mm)
Anti-Vibration Fan Mounts (Retail mount, OEM mount)
AcoustiFeet: Anti-Vibration Soft Silicone Feet
|Anti-Vibration Fan Gasket||80mm, 92mm: US$6; 120mm:
|Anti-Vibration Fan Mounts||Not yet for sale|
A large part of silencing a computer is simply finding the quietest components
that suit the needs of the user. The parts that produce noise are hard drives, power supplies and fans. Using cool components and removing heat
from the system efficiently without high airflow (and concomitant noise) are also important. Once all of these
aspects have been looked after, it becomes much more difficult to reduce noise
because it is the small details that matter. Improvements are no longer dramatic
AcoustiProducts has built its business around taking care of these small details.
Most of their products involve sound damping in some way by absorbing, reflecting
or redirecting sound and vibration. Although they are best known for their case-damping
product, AcoustiPack, they also make a number of other products. Recently, they
sent SPCR a number of silicone-based products designed to minimize vibration.
In a system built from low-noise components, vibration can still cause noise. Vibration comes from the same sources as
airborne noise: Components with moving parts, such as drives and fans. The basic
strategy for reducing vibration-induced noise is to isolate the vibrating component
from the case, as it is usually resonating case walls that convert
the vibration into audible noise.
Two of samples are fan isolation products that should appeal to those
who don’t have the inclination to find their own solutions. One is a 2.5mm thick
silicone fan gasket, available in the three most common fan sizes:
80mm, 92mm, and 120mm. The other is a set of silicone grommets that take the
place of conventional screws. The last product is AcoustiFeet, which is intended
to reduce the amount of vibration that is transferred from the system case to
its surroundings — a wooden desk or floor, for example.
Clockwise from the top: Fan mounts (retail), fan mounts (OEM), AcoustiFeet (black,
translucent), fan gaskets (80mm, 92mm, 120mm)
Determining Product Color
The Fan Gaskets and AcoustiFeet in this review are available
ANTI-VIBRATION FAN GASKETS
Features (from AcoustiProducts’ web
|Ultra-soft (unlike similar products) – Shore A 40||Shore A is a metric for measuring softness. It is quite soft, similar to the hard drive grommets in the Antec P180 case, perhaps akin to the silicone caulking used around bathtubs.|
|Not just 1mm thick like other fan gaskets – these are
|The extra thickness is supposed to do a better job of absorbing
|Compatible with virtually all case cooling fans||Just make sure you buy the right size.|
|Supplied with unique screws and soft silicone washers||This ensures that the screws don’t transmit vibration
through the gasket.
| Quick and very easy to fit (these gaskets ‘hold
onto’ the fan whilst fitting them due to a small lip in the gasket design)
|How easy? Keep reading.|
|Can be used with an external fan grille, for
maximum airflow and minimum wind noise
|Grill sold separately.|
The 120mm gasket is too large to hold its shape properly.
AcoustiProducts’ fan gaskets come in three sizes and two colors, but they are
all essentially the same. The product
page for the gaskets does an extensive job of explaining why you should
do something as esoteric as soft-mounting your fans. It also touches on some
of the technical details, such as the softness and thickness of the silicone.
According to the web site, the gaskets are intended to do two things:
No claim is made about the impact of the gasket on noise; the customer must
infer on his own that the reason for reducing vibration is to reduce noise.
This inference is quite reasonable — soft-mounting a fan is a standard
technique to reduce vibration noise. It is worth pointing out, though, that
it is one of the last steps of silencing a system; its impact is most noticeable
when the loudest sources of noise have already been dealt with.
The retail package contains the gasket itself, four silicone washers, and four
extra long screws to compensate for the additional thickness of the washers
and the gasket.
Installation is quite simple. First, the gasket is fitted over the fan and
a washer is fitted onto each screw. Then, the fan is screwed into place just
as an ordinary fan would be. It’s important not to tighten the screws too much,
as the silicone is most effective at damping vibration when it is not compressed.
This process works well for the 80mm and 92mm gaskets, but the 120mm gasket
has a tendency to come off the fan during installation — the silicone is
too soft to hold its shape properly when it is this big. I found an alternate
method of installation worked better: Attaching the gasket to the case with
the screws, and then adding the fan separately.
One word of caution: AcoustiProducts recommends that these gaskets should not
be used in high-heat applications, such as on heatsink fans. The reason for
this is probably the tendency of silicone to become sticky or even melt under
heat. The maximum operating temperature — 70°C — reflects this.
ANTI-VIBRATION FAN MOUNTS
Two slightly different versions of the fan mounts are available: On top
is the "retail" version, while the bottom is the "OEM" version.
At the time of writing, the anti-vibration fan mounts that we were sent are
not listed on AcoustiProducts’
web site, and do not appear to be for sale anywhere. The only hint that
they exist is an item under the "Latest News" section:
"NEW ultra-soft fan mounts are due for release shortly. An easy to fit,
cost effective solution to vibration noise from PC fans – more shortly!"
AcoustiProducts already sells what they call "Anti-vibration gel fan mounts",
which are essentially silicone sleeves for fan screws. However, in order to
use them properly, the mounting holes on the case must be enlarged, which not
everyone is willing to do. The new mounts do not require this modification,
as they do not rely on screws at all. Instead, they are designed to take the
place of screws.
The new fan mounts are quite similar to another product that is popular
in the silencing community: E-A-R
Fan Mounts. This product has been available for years as a way to
soft-mount fans. Compared
to the EAR mounts, the AcoustiProduct mounts are softer and easier to bend.
They are made of soft silicone, while the EAR mounts are made of some
kind of synthetic rubber compound.
The fan mounts come in two versions, one labeled a retail version and the other OEM. The only difference is in the
method of installation. The OEM mounts can be mounted on a fan before it is
installed, whereas the retail mounts must be installed on the case before the
fan is installed. This makes the OEM version slightly more versatile and easier
to install, but it leaves a silicone nub sticking out of the back of the case,
which is not as aesthetically pleasing. Installation aside, the two versions
should perform identically.
No matter which version is used, installation is a simple matter of pulling
the mount through the existing screw hole in the case and then threading it
through the corresponding hole in the fan. It takes a little force to pull the
mount through, but it comes through with a satisfying "pop" and is
completely secure thanks to the wide flange. Even fans with closed-style mounting
holes can be used, as the mounts should grip the inside of the mounting holes
with friction alone.
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:
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
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 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
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:
AcoustiFeet: Maximum Weight and Recommended Applications
product web page)
Light weight PC & SFF PC cases, HTPC cases, vibrating
HiFi units, TV and home cable set top boxes, small speaker cabinets, inkjet
Medium-to-light weight PCs, solid SFF cases, heavy HTPC
cases, larger inkjet printers and laser printers, heavier HiFi units (such
as power amps), speaker cabinets etc.
Medium-to-heavy weight PC cases (suitable for the majority
of PCs), larger Macs (like the G5), large laser printers, large speaker
Seriously heavy PCs and Tower Server cases – heavier PCs
with multiple HDDs, tower-style case servers, other applications like
noisy photocopiers and office equipment etc.
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.
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.