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Putting it all together
We have so far designed cooling solutions for the chassis and for the three hottest components. It is time to put it all together and run a few benchmarks to see if weve achieved our goal. Building a silent workstation is not very different from building a regular PC. The only thing to keep in mind is overall tidiness, attention to detail. and cable management. As with any PC build, you need to follow the manufactures guidelines and recommendations. Also, join a reputable PC-building forum, such as Silent PC Review, and ask questions. The biggest issue is component compatibility, both in terms of hardware and software. Make sure the operating system you choose supports all of the hardware you plan to use. Workstation building is a craft that requires careful planning, patience, and a little bit of creativity. You can be sure that all of the components chosen for this build are compatible with one another and work perfectly with Windows 7 64-bit as well as with Linux Ubuntu 11.04. Heres the hardware inventory:
- Intel Core i7 Sandy Bridge 2600K CPU
- Intel DP67BG socket 1155 motherboard
- Kingston HyperX Grey Series 240-Pin DDR3 SDRAM DDR3 1600 RAM (16GB)
- Antec CP-850 power supply
- EGVA NVIDIA GTX460 video card
- OCZ Vertex 2 120 GB SSD
- SAMSUNG EcoGreen F4 2TB hard drive
- Western Digital Green 2TB hard drive
- LiteOn DVD reader/writer
- Antec P183 V3 chassis
- Gelid 120MM PWM fan
- Scythe 120MM PWM fan (x3)
- Thermalright HR-02 CPU heatsink
- Thermalright Shaman VGA cooler with the TY-140 fan
I benchmarked the system with Prime95 to stress-test the system and measure temperature increase from idle to full load. At idle, the CPU and GPU hover around 30C, while at full load (30-min of 100% load testing) the CPU reaches around 65C while the GPU peaks at around 60C. Of course, these temperatures will differ slightly depending on the ambient temperature in your work environment as well as your fan speeds. The most important result is, of course, the total noise output, both at idle and at full load. The workstation performs as expected. At one meter away, it is inaudible in my office and lab environment. This simple result has taken a lot of research and planning, but it has been a thoroughly satisfying experience. I hope you give it a try yourself. Know that it is currently the only way to make sure your workstation is powerful, stable, cool, and, most of all, virtually silent.
Figure 1 shows the finished system inside the Antec P183 V3 chassis. Figure 2 is a screen shot of CPUID Hardware Monitor software. The fans, controlled by the Intel BIOS, run at low speeds, thus keeping the system quiet. Finally, you can further improve cable management and the overall looks of your build by individually sleeving the PSU cables or making sleeved extensions (Figure 3). Yes, it is perhaps superfluous, but it can be utterly fun. Good luck with your build and be sure to email me with questions.
Figure 1. The finished system
Figure 2. Fan speeds
Figure 3. Individual cable sleeving
Much thanks to Bartek Plichta for this highly valuable contribution to SPCR!
If you have any interest in acoustics including excellent reviews of microphones and related audio gear or linguistics, check out Bartek's unique site, http://bartus.org/akustyk/
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Discuss this article in the SPCR Forums.
Quantifying noise performance
Quantifying noise performance is tricky. It is virtually impossible to come up with a fully satisfying approach for the purposes of this article. Remember, our ultimate goal was to build a workstation that will not be audible from the distance of 1 meter, in a typical, quiet research environment. Of course, ambient noise levels are going to differ dramatically from lab to lab, so if your laboratory happens to house, say, huge power generators, even a relatively loud PC is going to appear whisper quiet. One might, therefore, ask, why not just measure noise levels and report them "objectively?" Well, it is not that simple. Yes, in theory noise measurement can be more "objective" but there are many, potentially confounding variables at play. The fields of audiology, hearing science, psychoacoustics grapple with this problem on a daily basis, and researchers still do not fully agree on how to measure noise "objectively."
Part of the problem is ambient noise levels (also referred to as "the noise floor") in the testing environment. For the most accurate noise measurements, the testing environment must have an extremely low level of ambient noise and be free from electromagnetic interference. Anechoic chambers are designed to obtain precisely this type of environment, but even the most expensive and technologically advanced anechoic designs vary greatly in their "noise floor." For example, the anechoic chamber at Michigan State University has the noise floor of about 15 dBA. But, what exactly does that mean? Is this an absolute value, such as, say, somebody's height? Not quite. Decibel scales differ from one another, partly, because they use different reference levels and weighting filters. And that gets complicated, as well.
Say we want to use a scale that best corresponds to human hearing. After all, we want the workstation to be virtually silent, as perceived by our own ears. Human hearing is greatly variable and non-linear, i.e., it performs differently for different types of sounds. I think you can already see the problem there. We would not be able to properly characterize noise levels in reference to human hearing by using just one number. We would need to characterize the entire audible spectrum, between 20 and 20,000 Hz. The next question is whether we should apply an octave-band, a third-octave-band, or a critical-band filter? On a linear or logarithmic scale? Then we get into periodic versus transient sounds, bandwidths, overtones, resonant frequencies... the list goes on.
It is equally difficult to compare our results to those published by workstation manufacturers. We would need to know all the details of their testing procedures, instrumentation, methodologies, etc. It is simply not possible, so we have no choice, but to take their numbers in good faith, or rely on independent reviewers such as Silent PC Review.
Given all the complications related to quantifying noise performance, I decided to make digital recordings of my quiet research environment (a sound-treated, audiology lab) with the workstation off and on (at idle and full load). To give you a better idea of what the levels are, figure 4 shows octave band maximum permissible ambient noise levels for each test frequency range and ANSI S3.1-1977 levels for comparison.
Figure 4. Octave band maximum permissible ambient noise levels for each test frequency range and ANSI S3.1-1977 levels for comparison
I decided to use the same recording technique as that I use in my microphone reviews. The idea is to give you a reasonable comparison of the PC noise levels with typical conversational speech. This should give you a decent indication of how much above a very quiet lab ambient noise level the workstation-generated noise appears to be. Loudness is in the ears of the beholder, so you be the judge! Here's how I suggest you listen to the recording:
- Open the MP3 file in your playback application (e.g., Windows Media Player, iTunes, etc.).
- Listen to the speech sample and set the volume at a level that, subjectively, would similar to that of someone talking to you from about a meter away.
- Listen to the entire sound file, which starts with 0.5 s of pure tone (377 Hz), followed by speach, then pure tone, ambient noise, pure ton, PC noise at idle, pure tone, and PC noise at full load (see Figure 5).
- Try to hear any differences among the three noise samples.
Download MP3 files, encoded with the LAME MP3 encoder at 128 kbps (mono). The maximum CPU and GPU temperature peaks at around 60C, with ambient temperature of around 25C. The recordings were made with the DPA 4006-TL microphone (reviewed here) at the distance of 1 meter from the workstation, an ultra quiet Tucker-Davis microphone pre-amplifier, and the Sound Devices USBPre A/D converter (reviewed here) at 48,000 Hz, 24-bit.
Figure 5. Waveform of the test recording
I have plotted long-term average spectra (LTAS) of each type of noise (200 Hz bandwidth). Figure 6 shows LTAS of ambient noise, while Figures 7 and 8 show LTAS of the PC noise at idle and full load, respectively. Note the clear change both in noise level, as well as character, with the most pronounced increased below 500 Hz, possibly caused by the low-frequency "hum" of the fans. At full load, an additional peak shows up in higher frequencies, possibly the result of the PSU fan spinning faster due to a significant increase in both power and temperature during the test. Still, the Antec CP-850 PSU remains relatively (and surprisingly) quiet throughout.
You will recall that the fans operate at rather low speeds (Figure 2 above), thus the increase in noise is rather small and barely perceptible (at least to my ears) at the distance of 1 meter from the workstation.
Figure 6. LTAS of ambient noise
Figure 7. LTAS of PC noise at idle
Figure 8. LTAS of PC noise at full load
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