Hardware Reference
In-Depth Information
Choose quiet case fans
Most modern systems have at least one supplemental case fan, and some
have several. The more loaded the system, the more supplemental cool-
ing you'll need to use. Use the following guidelines when selecting case
fans:
• Case fans are available in various sizes, from 60 mm to 200 mm. All
other things being equal, a larger fan can move the same amount of
air with less noise than a smaller fan, because the larger fan doesn't
need to spin as fast. Of course, the fan mounting positions in most
cases are of fixed size, so you may have little choice about which size
fan(s) to use. If you do have a choice—for example, if the case has two
or three fan positions of different size—use the largest fan that fits.
• Case fans vary significantly in noise level, even for the same size and
rotation speed. Many factors come into play, including blade design,
type of bearings, grill type, and so on. In general, ball bearing fans are
noisier but more durable than fans that use needle or sleeve bearings.
• The noise level of a fan can be reduced by running it at a lower speed,
as long as it moves enough air to provide proper cooling. The simplest
method to reduce fan speed is to install an inline resistor to reduce
the supply voltage to 7V. These are available from the sources listed
earlier, or you can make your own with a resistor from Radio Shack or
another electronics supply store. Some fans include a control panel,
which mounts in an available external drive bay and allows you to
control fan speed continuously from zero to maximum by adjusting a
knob. Finally, some fans are designed to be controlled by the power
supply or a motherboard fan connector. These fans vary their speed
automatically in response to the ambient temperature, running at
high speed when the system is heavily loaded and producing lots of
heat, and low speed when the system is idle.
• The mounting method you use makes a difference. Most case fans
are secured directly to the chassis with metal screws. This transfers
vibration directly to the chassis panels, which act as sounding boards.
A better method is to use soft plastic snap-in connectors rather than
screws. These connectors isolate vibration to the fan itself. Better still
is to use the soft plastic snap-in connectors in conjunction with a
foam surround that insulates the fan frame from the chassis entirely.
The preceding six elements are the major steps required to quietize your PC.
Once you minimize noise from those major sources, you can also take the fol-
lowing steps to reduce noise from minor sources. Some of these steps cost
little or nothing to implement, and all contribute to quieting the PC:
Put the PC on a mat
Rather than putting the PC directly on your desk or the floor, put a sound-
deadening mat between it and the surface. You can buy special mats for
this purpose, but we've used objects as simple as a couple of mouse pads,
front and rear, to accomplish the same thing. The amount of noise reduc-
tion from this simple step can be surprisingly large.
