Viewing page 2 of 5 pages. Previous 1 2 3 4 5 Next
Noise reduction strategies
Figure 1 shows a simple system built around the Lian Li A05NB case. I have labeled the typical components that you will need to build a basic workstation. Can we simply get rid of the noisy components? Having identified the most common sources of computer noise, we can now move on to discussing some of the most effective noise reduction strategies. The obvious question one should ask is whether we can get rid of any of the noisy components. Since our goal is to build a powerful and versatile workstation we cannot really skimp on too many components. However, I believe that we should try to get rid of at least the optical drive. These days, you can install all of the applications from the network and even the operating system can be easily installed from a USB memory stick. Yes, I realize that in some administrator-managed university computing environments software is distributed on optical disks only, but, one would hope, these policies will change and the optical disk will become obsolete soon.
Figure 1. An Intel Core i7 system built inside the Lian Li A05NB chassis. The labels indicate some of the typical components you are likely to use in a workstation.
What can we get rid of next? How about the hard drive? At this time (summer of 2011), we can install the operating system and all the applications on a solid-state drive (they are virtually silent), and use spinning drives only as data storage. For some workstations, data can be stored on a network-attached storage system (NAS), but for most of us, it is not a good idea. We need to run experiments, record audio and video, capture participant responses, etc., all of which require fast and stable data throughput. Therefore, let's assume that every workstation is going to have to have an SSD and two at least two 2TB hard disk drives, possibly more.
Can we get rid of the GPU? I think that, in some cases, we can get rid of the discrete GPU altogether, but only if the workstation is controlled by a remote desktop connection from another machine and does not require any GPU-specific programming. All modern operating systems allow the control of a workstation desktop via the network. This requires another computer, with a GPU installed, a monitor, keyboard, and mouse connected to it. For example, the "headless" workstation may be located inside a sound-proof booth and used to collect participant responses, while the control PC is in the adjacent lab, behind a sound-proof window. I believe this is a rather rare scenario, but a very real one, nevertheless. Thus,if your workstation involves this particular use case, it can, in theory, be built without an add-on GPU card. In all other cases, we will need to make sure the power supply, the CPU, the GPU, and the hard disk drives are all kept cool and quiet.
Passive and active cooling
The progress in semiconductor manufacturing has enabled Intel, AMD, NVIDIA and others to create physically smaller, more powerful, and more energy efficient chips. Some of the less powerful chips do not require dedicated active cooling. They do generate heat, but the amount of heat is small enough to be effectively dissipated by air circulation within the computer chassis. Is it perhaps possible to build a workstation entirely out of such passively cooled components? Unfortunately not. I believe that a modern research workstation must be built of components that will perform all of the required processing with ease and with a great deal of headroom. We must, therefore, focus on providing efficient and silent cooling.
This brings us to an important point in our discussion. There are two approaches to active cooling, namely liquid cooling and air cooling. Obviously, liquid cooling has more headroom, and is more effective in cooling extremely hot components. However, unless a truly elaborate, expensive, and physically large passive radiator system is used, liquid is going to have to involve several fans spinning at high speeds in order to facilitate efficient heat exchange between the radiators and the surrounding air. Perhaps ironically, liquid cooling simply requires too many noisy fans to be satisfactory for our needs. I argue that air cooling is the best choice for our silent workstation. It is efficient enough, yet reliable, inexpensive and relatively easy to implement.
I have seen several labs where the workstation is covered with sound dampening foam. Perhaps, intuitively, this might like a good idea, but it certainly is not. We should always keep the PC in a relatively well-ventilated area to facilitate efficient heat exchange. However, the chassis itself can play an important role in reducing the PC's overall noise output. Computer cases are rarely optimized for noise reduction, but there are a handful of models that provide decent acoustic isolation. When choosing a chassis for your silent workstation, you should look for cases that provide some form of sound dampening and anti-vibration hardware mounting options. Of course, the case must also provide adequate air circulation and have the necessary expansion and good cable management capabilities.
For the purposes of this build, I have chosen the Antec P183 mid-tower case, but there are other equally good alternatives available (e.g., Fractal Design Define R3). The case comes with sound-treated side panels (a three-layer design) and anti-vibration hard drive mounts. Also, it uses a proven ventilation system with two intake in the front and two exhaust fans (one in the back and one in the top). The case is divided into two different thermal chambers to further facilitate airflow. It is important to point out that good air circulation is crucial to quiet operation because it allows fans to run at relatively slow rotational speeds, and, as a result, more quietly.
Obviously, you don't have to use the Antec P183 if it doesn't work for your needs. What should you look out for when buying a chassis for a silent build? Here are some points to consider.
The case must be large enough to accommodate all the components with ease, giving you plenty of room to work with.
The case must have good ventilation options. I recommend using the proven design of front intake and rear exhaust fans. The top fan is optional. You should use fans of 120 mm in diameter. Larger fans, especially 140 mm, can also be used, but there are far fewer silent options available in sizes other than 120 mm.
You must be able to do proper cable management to facilitate good air circulation. Look for cut-outs in the motherboard tray for routing cables and for enough room (say, at least 15 mm) between the back of the motherboard tray and the right side panel for tucking your cables away. Figures 2 and 3 show the cable management options of the small Lian Li PC-A05N case. The power supply and SATA cables are secured with adhesive cable anchors and zip ties. All cables are tucked away and do not obstruct airflow inside the chassis.
Figure 2. Cable management of Lian Li A05NB chassis (back)
To further facilitate cable management, be sure to use a modular power supply, such as the Antec BP550 Plus 550W. A modular power supply allows you to connect only the cables you need, thus substantially reducing cable clutter. More details about power supplies are included further on.
Figure 3. Cable management of Lian Li A05NB chassis (front)
It is crucial for the case to use rubber grommets for mounting vibrating components, such as fans and hard drives. Figure 4 shows rubber fan pins that are very effective at preventing fan vibrations. You can also use rubber dampeners for fans and power supplies (Figures 5). They are installed between the vibrating component and the chassis to further decrease noise levels.
Figure 4. Rubber fan pins. They are easy to use and effective in preventing vibrations.
Figure 5. Sound dampening rubber gaskets for a power supply (black) and a 120 mm fan (white)
You need some sort of acoustic treatment (sound dampening) to prevent the fan noise from leaking outside the chassis. Some cases come with pre-installed acoustic foam or bitumen but you can easily apply acoustic treatment yourself, provided the case have enough room for it.
The case can be made either of aluminum or steel, with some plastic parts usually used for the front bezel. The construction must be sturdy and made with tight tolerances in order to prevent unnecessary vibrations. There's a debate on whether aluminum cases provide better cooling, but we don't need to concern ourselves with that. Be prepared to be pay a little extra for a sturdy case. Try solid brands, such as Antec, Fractal Design, Silverstone, or Lian Li, and stay away from the entry-level cases. You should expect to spend around $100-150 (US) for a decent case.
It is important for the case to have sturdy rubber feet (avoid the flimsy adhesive ones) to keep the body off the floor and prevent vibrations.
Proper placement is crucial to proper air ventilation. I realize that labs and offices have limited space to spare, but try to place the system in a well ventilated area, away from the wall or furniture. Make sure the spot is clean and free from dust. If you are going to put the case in a closet or locker, be sure to install ventilation fans.
The 60-Hertz hum is a proper curse of acoustics laboratories. It is quite difficult to avoid it, especially in old buildings, with old power lines. I have written extensively on preventing hum in sound recording, and the same ideas apply here. Be sure to use a high-quality uninterruptible power supply (UPS) and a surge protector. Use properly grounded cables and outlets. Finally, try the Ebtech Hum-X for filtering out unwanted voltage on the ground line. You can read more about it in my review.
|Help support this site, buy from one of our affiliate retailers!|