AcoustiPack Noise Damping Kit

Cases|Damping
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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 70x25 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.

TEST 1
undamped Sonata
damped Sonata
Heard The overall noise of the fan dropped a lot compared to having it outside the case. There was much less whine, and maybe a bit more lower frequency noise. The latter could have been caused by both cavity resonance as well as case vibration, which could be felt with the fingers. This is so loud I would toss it out the window in 20 minutes if I had to work with it. The whine became much more subdued than in the undamped case and the overall noise dropped further. There was less case vibration, and somewhat less low frequency noise. It became more wind noise than whine, but was still too loud. Most of the sound emanated from the outflow vent on the back panel. In comparison, there was very little noise coming through the top, sides or front of the case.
Measured 4" from front panel mid-height* 55 dBA; 6 KHz peak no longer visible. Highest peak now around 500 Hz. 48 dBA; 6 KHz peak even less visible. Highest peak around 400 Hz.
Measured 2" from back panel exhaust hole* 63 dBA; 6 KHz peak almost unchanged from free air. 500 Hz peak also in evidence. 56 dBA; 6 KHz peak clearly visible but less pronounced. Highest peak around 400 Hz.

*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.

TEST 2 - back panel sealed
undamped Sonata
damped Sonata
Heard The overall noise was lower than in Test 1. There was less whine. It was still so loud I would toss it out the window if I had to work with it. Maybe not in 20 minutes, but half an hour? The whine became even more subdued than in Test 1 and the overall noise was lower again. Low frequency noise. There was also less wind noise, but it was still too loud.
Measured 4" from front panel, mid-height 56 dBA; 6 KHz. peak no longer visible. Highest peak around 500 Hz. 48 dBA; 6 KHz. peak even less visible. Highest peak around 400 Hz.
Measured 2" from back panel, mid-height 58 dBA; 6 KHz. peak no longer visible. 500 Hz peak also in evidence. 50 dBA; 6 KHz. peak even less visible. Highest peak around 400 Hz.

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.
Recordings of PC Noise (MP3)
Thermaltake Volcano 7+ fan, FD12702598-2F at 12V, 12" Warning: This is very loud, but if you turn the playback volume down too low, you may not be able to hear the Panaflo without turning the volume back up, thus spoiling your comparison.
Volcano fan in undamped Sonata case, mic in front
Volcano fan in damped Sonata case, mic in front
Volcano fan in undamped Sonata case, mic in back
Volcano fan in damped Sonata case, mic in back
Panaflo FBA08A12L fan at 12V, 12 inches When played on a reasonably good pair of speakers or headphones, this recording gives you a good idea of the smooth quality of the Panaflo 80mm Hydrowave bearing fan noise and why it remains SPCR's reference. Comparing between this and the first (Volcano fan) recording is really educational.

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.

TEST 3 - Panaflo 80L fan as noise source
Noise
undamped Sonata
damped Sonata
Panaflo 12V The overall noise was low. A bit of whine could be heard from the Panaflo but it was modest. From the rear exhaust vent, the Panaflo fan noise became more audible. The fan noise from the PSU made more low frequency noise than the Panaflo. The hard drive seemed to contribute a bit to the low frequency noise as well, but it was difficult to separate out. The overall noise was lower than with the undamped Sonata. Virtually no whine could be heard from the Panaflo inside, except when listening right at the back exhaust vent. The fan noise from the PSU became the bigger noise source. The hard drive noise was even harder to identify
Panaflo 7V The overall noise was very low, not much different than the Panaflo at 12V in the damped Sonata case. The Panaflo could not really be heard. Most of the noise came from the rear, from the PSU fan exhaust. The hard drive seemed to contribute a bit to the low frequency noise as well, but it was difficult to separate out. The overall noise was the lowest of all, but not by a big margin. The PSU fan exhaust seemed to be the only source of any noise. The hard drive noise was very hard to identify

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.

* * * * *

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.

* * * * *

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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