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THE MEDIA PC
The way a media PC is used is substantially different than the
average desktop PC. The most important differences are noted below.
Normal Home PC
On equipment rack, near TV / stereo
On desktop next to monitor or on floor under / beside desk
Play & record music and video, download & serve media files, play
games; usual PC functions secondary.
Office, creative, engineering, scientific and communication work; gaming;
watch/play video & music; video encoding, etc.
Typically >2 meters away.
Typically not more than 1 meter
Background + PC noise + noise from other A/V equipment + conversation
+ music/soundtrack playing from TV/stereo speakers
Background + typing noise + noise generated by PC, perhaps background music
In a nutshell, the media PC is usually situated near the TV, which is usually at least six feet away from the seated viewers. The noise in the room includes whatever is being played through the speakers of the A/V system, plus any noise made by other A/V gear. From first hand experience, we know that...
Many digital TV boxes and PVRs contain a noisy hard drive and fan(s).
The HDD is usually on all the time, as long as the unit is plugged
in. This means the noise is always there, whether you're using the gear or
not. There is no care in PVRs to ensure low acoustics; we've measured nothing
lower than 25 dBA@1m with several different PVR models. It's typically closer
to 30 dBA@1m or higher because the HDD is hard mounted to the chassis, and
the chassis then makes whatever it's sitting on resonate. The fan(s) in the
PVR are rarely very quiet, and they ramp up in speed when things get hot inside,
which is common given the way PVRs are usually crammed into poorly ventilated
shelves in AV stands.
Many high end (and not so high end) A/V receivers contain a fan that runs
almost all the time. This is usually not as intrusive as the HDD noise
in the digital TV boxes and PVRs, but still measure at least 20 dBA@1m.
Almost all rear projection TVs require at least one cooling fan to be
on constantly. The speed of this fan usually varies with internal temperature,
which naturally goes up the longer the TV is left on. The residual noise of
these TVs (with the speakers muted) is at least 30 dBA@1m. Of course, rear
projection TVs are extinct now, but they're still in use in many living rooms.
30 dBA@1m is about the absolute minimum level needed for
intelligibility of speech, given typical dynamics when the TV, movie or game
sound is turned on. Levels usually need to be much higher, with peaks
reaching ~60 dBA@1m, and averaging at least 40~45 dBA@1m. This depends a great
deal on viewer / listener habits, hearing sensitivity, housing setup, etc.
In general, sound levels for movies are higher, likely 10~20 dBA higher for
both average and peaks. This is also true of music listening: Most people
prefer higher levels for better realism. Typical peaks from an A/V system
playing music probably reach 80 dBA@1m, with the average being perhaps 10
dBA lower (depending on the type of music, of course.)
These are broad generalizations about the acoustic environment
for a media PC. Suffice it to say that we believe the acoustic environment for
a media PC will almost always be louder than for other types of
home PCs. Its noise will be masked by the sound from the speakers at
least until you hit the mute button, at which point the PC and other A/V equipment
noise may become very audible.
Just how quiet does a Media PC have to be to be inaudible?
If the HTPC is in a multi-purpose room, and you still want quick and instant access to its media functions, then it will have to stay on. Then the idle HTPC noise will be there for you to hear whenever you are in the room, whether you're using the equipment (ie, have the sound on) or not.
Because of these factors, most users tend to accept a higher level
of noise from a media PC case that they might not accept in a quiet home office
or bedroom. A perfectly acceptable SPL in most cases is 20 dBA@1m (or even several
dB higher, depending again on conditions). When the system is in use, such a
level will be completely inaudible.
However, some users are bothered by even modest noise in the midst
of quiet passage of music or in a dramatic cinematic moment. If you are one,
then obviously you will want to shoot for the lowest noise level from your HTPC.
Ditto if your media PC is always on in a living room that's otherwise free of
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