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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.

Criteria
Media PC
Normal Home PC
Location
On equipment rack, near TV / stereo
On desktop next to monitor or on floor under / beside desk
Application
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.
User Position
Typically >2 meters away.
Typically not more than 1 meter
Overall Acoustics
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 noise.




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