Studios & Silence: AES Student Summit in St. Louis

The Silent Front
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STUDIO-WORTHY COMPUTERS

The need to build a studio-worthy system prompted a bit of rumination on our part about tuning a system in studio-specific ways. The point of having a quiet system in a recording environment should be fairly obvious. A low, computer-free noise floor means a purer reproduction of whatever is being recorded. However, until we actually had to put together a presentation on the subject, we had never thought through the specific needs of a recording studio.

SPCR has always advocated evaluating noise subjectively in addition to using objective measurements. This remains true in the studio, but it pays to know what you're listening for because recorded sound behaves a bit differently from live sound. In real life, we are generally able to tune out much of the background noise. Microphones don't do this — they record the background along with the foreground. Sometimes this doesn't matter too much — a thrash metal band recorded at 120 dB will blast out all but the loudest background disturbances. But, there are also many musical genres where quiet pauses are quite common (jazz and classical come to mind) and equally many recording situations where background noise, i.e. ambiance, features strongly — radio and film, for example.

In these situations, a quiet background becomes essential because, once it is picked up in the recording, it is liable to be amplified above its original level — especially in material where the signal is dynamically compressed to bring the quieter sections closer to the louder ones. That faint electronic squeal that you can ignore because it's quiet gets much worse when it's amplified 10 dB. Recorded ambiance draws attention to itself even when it's played back close to its original level because it is directional — our ears can source it to the speaker, and we therefore pay more attention to it than we did when it surrounded us in real life. What this means is that the quality of the noise is doubly important in studio applications. A noise signature that is tonal enough to color a studio's ambiance is not just annoying — it's unacceptable for recording.

Dynamic changes where the ambiance shifts from one noise signature to another are even worse. Even if the change is too slow to draw attention to itself when it happens, it's possible that the recording may need to cut — and if the ambiance is different on either side of the cut, the sudden change will draw attention to itself.

With this in mind, the subjective quality of the noise in a studio system is actually more important than the noise level. A 23 dBA@1m system may be better for recording than a 21 dBA@1m system if its noise character is broadband and the quieter system is not. Of course, the best systems (as always) combine the advantages of both, but it's worth bearing in mind that a quiet studio system means something a little different from a quiet home office system.

Computer noise can be a problem in other places too — the mixing room, for example. Forcing your brain to tune out the constant drone of computer noise while you're mixing changes the way you hear — and thus the creative choices that you make while mixing.

Enough theory. The prize system that we built demonstrates all of this. Pay attention to the aspects that primarily address noise quality: The drive suspension, the grommet-mounted fans, and the sound damping. All of these are advanced techniques that go beyond just picking the right off-the-shelf parts. All of them are aimed at reducing secondary noise — resonance — rather than targeting the primary noisemakers (the fans and the hard drive). This is how you improve noise quality. Resonances are nearly always tonal, so getting rid of them goes a long way to leaving only the broadband turbulence noise of the air blowing through the system.

So, what does a weekend of audio geekery come down to for SPCR? New testing equipment, new ways of looking at old problems, and a chance to spread our knowledge in new places. We'd like to thank forum user souagua for inviting us down to St. Louis, and everyone at Webster for hosting a great event.

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SPCR Articles of Related Interest:
What is a "Silent" Computer?

CES 2008, Day 1Days 2 & 3
SPCR's Test / Sound Lab: A short Tour

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