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BEFORE / AFTER COMPARISONS
To determine the effect of MuteMat Plus on our test system, detailed notes
were made about how the system sounded in three activity states, before and after MuteMat was installed:
- System Idle
- Hard drive seeking
- Optical drive spinning
These activity states cover the whole range of noise that the system
can produce. Load testing was not done, as the noise would be the same as in idle; there are no thermally controlled fans.
System Idle
Before: The system measured a respectable 24 dBA@1m: Quiet enough that it
could easily be tuned out, but loud enough
that it was still clearly audible above the low ambient noise level of the test lab. The character
of the noise was fairly benign, with few pure tones. The bulk of the
noise was in the lower frequencies. I would describe it as a low hum or growl.
There was also a significant amount of broadband airflow noise easily
noticed on close listening.
The main source of noise was the Antec TriCool exhaust fan. Stopping it temporarily
made a big difference to the noise level. Aside from that, most of the noise
seemed to be resonance, the source of which could not be easily pinpointed.
MP3:
Test system without MuteMat Plus, Idle (24 dBA@1m)
After: MuteMat had very little effect. Both
the volume and quality of the noise were largely the same as before. The measured
noise level was identical. The balance between the low hum and the airflow may have changed
a little, with the airflow becoming more noticeable and the hum receding further into
the background, but the change was minor if it was there at all. A comparison
between the two recordings confirmed that there was very little change.
MP3: Test
system with MuteMat Plus (24 dBA@1m)
Hard Drive Seek Noise
Before: Seek noise was one of the worst aspects of system noise
during the baseline test. The Western Digital Raptor is a fairly quiet drive
when idling, but its seeks are sharp and loud, and stand out against the otherwise quiet idle noise. Despite
the intrusive nature of the sound, the measured noise level was only 26 dBA@1m.
The noise recording below was done while the drive was being defragmented. This gives a good idea of what the drive sounds
like, but it doesn't drive home how irritating the seeks can be when they are
intermittent, which is typical during general PC use. For me, variability is the worst part
of seek noise.
MP3:
Test system without MuteMat Plus, HDD Seek (26 dBA@1m)
After: MuteMat Plus made a noticeable difference with seek noise. The noise became much less sharp, more broadband
and muted. Instead of having my attention drawn to the seeks every time Windows
decided to hit the swap file, I had to actively listen to
hear the seeks. The measured noise did not drop by much though — maybe a decibel.
It is possible to get a sense of how MuteMat changed the quality of the noise
by comparing the two recordings, but they don't quite illustrate the significance
of the difference, perhaps because they are recorded at a distance 3",
while most users will be seated closer to a meter away. Because the muted seek noise became much
more broadband than the original noise, it was harder to distinguish
the seek as you moved away from the source of the noise.
MP3: Test
system with MuteMat Plus, HDD Seek (25-26 dBA@1m)
Optical Drive Noise
When they are in use, optical drives are often the worst noise offender in
a quiet system. Their proximity to the front of the case (and thus the user),
the difficulty of soft-mounting them, the variability of the noise, and the
inherently unbalanced nature of optical disc media all contribute to the loud noise
of optical drives. Because of this, four separate tests were run with the optical
drive to get a good idea of what it sounded like. All tests were done with a
disc in the drive; without any media loaded the drive was effectively silent.
- Drive idle, case door closed
- Drive in access mode, case door closed
- Drive idle, case door open
- Drive in access mode, case door open
"Idle" and "access" refer to the speed that the disc was
spinning inside the drive. The "access" mode could be reliably induced
by leaving the autorun window that pops up after inserting the disc. "Idle"
refers to the baseline noise of the disc spinning after the autorun window was
closed. Each state was tested with the case door open and closed to determine
what role the door played in damping the noise.
Before: The generic optical drive in this system did not sound nice,
even at the basic "idle" level. This is reflected partially by the
high SPL measurement — 28 dBA@1m — but the recording is a better
demonstration of how the drive destroys the otherwise smooth character of the system
noise. Even at idle, the optical drive added a rough midband clatter to the system. It's
possible that the drive had a loose bearing, as there is a distinct rattle
that sounded a bit like muted hard drive seeks.
With the drive in access, the midband noise became significantly louder,
and the measured noise went up by 3 dBA to 31 dBA@1m. The spindle motor noise
sounded like heavy machinery operating in the distance. There was a slight
warble or throbbing to the noise that made it difficult to tune out. The
rough rattle at idle was still present, but it did not increase
in volume like the motor noise, so it was less noticeable than before.
Opening the door, at any optical drive speed, made high frequency
noise audible, along with a rough "ch-ch-ch".
In addition, the basic motor noise became louder and rougher in character.
When the drive was spinning, the distant machinery sound became louder, along with the warble, especially in the
lower frequencies.Strangely, the measured SPL did not change with the door open, suggesting that all the heard differences were qualitative.
MP3:
Test system without MuteMat Plus, Optical Drive at Idle, Case Door Closed
(28 dBA@1m)
After: The biggest drop in measured noise came when
the optical drive was tested. With the case door closed, the idle noise dropped
a decibel to 27 dBA@1m, while the in use noise dropped 2 dBA to 29 dBA@1m.
Opening the case door lessened the change, although it still measured slightly
lower with the drive in use — 30 dBA@1m compared to 31 dBA@1m.
The measured noise says
very little about how the noise actually changed. At idle, the roughness of
the noise became smoother, changing from a midband drone to a low frequency
hum, making it more difficult to distinguish it from the rest of the system noise. A slight high frequency buzz was all that remains of the rattle.
The improvement was no less noticeable when the optical drive was in use. It sounded more like a medium-speed fan than heavy machinery. The primary noise
turned into a low drone and a small amount of airflow noise.
Even with MuteMat in place, opening the door increased the noise. At idle, the main
noise was the "ch-ch-ch" described before, perhaps slightly softer in character. Although motor noise was rougher than with the
door closed, it was still better than without MuteMat.
With the optical drive in use and the case door open, it sounded a bit like
distant machinery again, although not as bad as before.
The biggest change was that air turbulence, not motor noise, now
dominated the noise character. The motor noise was not gone, but
not nearly as intrusive.
MP3: Test
system with MuteMat Plus, Optical Drive at Idle, Case Door Closed (27 dBA@1m)
CONCLUSIONS
MuteMat Plus is an interesting product, and a fair amount
of R&D has gone into its development. Like their main
competitor, AcoustiProduct, MuteMat goes to a lot of trouble to explain the science
behind the product, and does a good job of presenting it in layman's terms.
A damping product like MuteMat Plus is not the place to start when
silencing a system. If your components
are loud to begin with, acoustic damping materials really won't help much. This can be seen by the marginal difference it
made in the sound pressure level measurements. But, if you're looking for an improvement in the subjective noise quality with a PC that's already reasonably quiet,
MuteMat can definitely help. The most noticeable difference
is with noise sources that are rough or sharp — seek noise, for example.
MuteMat cannot
turn a loud PC into a quiet one, but it can improve system acoustics by smoothing the quality of the noise. The overall effect of MuteMat with our test system was to lower the overall frequency balance,
pushing some of the noise out of the more audible midband. It also did
a good job of smoothing out pure tones and changing the noise character towards
a less irritating, more broadband sound. Fans that buzz when undervolted, for example,
may be less of a concern with MuteMat installed.
Is it better than AcoustiPack? It's very difficult to say without applying the two materials in the same way to two identical system, and having an untreated third identical system as a control. Even then, I'd guess that the differences might be difficult to assess definitively. Suffice it to say that MuteMat seems like a good, viable alternative.
Mutemat is sold only in the UK at this time. The company does ship internationally.
* * *
Much thanks to MuteMat
for the opportunity to examine these vibration-reduction products.
Discuss this article in the SPCR Forums.
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