Reading a Studio Plan: What NC Curves and Cable Schedules Actually Mean
Two terms turn up in every studio design quote and drawing. Callum Rhodes explains noise criteria and cable schedules in plain words, and what to ask for when you see them.
6 minutes to read
Why two small terms decide so much
When a studio drawing arrives from a consultant, most producers look at the floor plan first and skim the notes. Yet two items in those notes, the noise criteria target and the cable schedule, tell you more about how the room will behave than the layout does. A studio can look right on paper and still hum, ring or leak sound into the corridor if these two are vague.
I come to this from the camera and workflow side, not the acoustics side, so I explain them the way I wish they had been explained to me. Both terms sound technical, but each answers an ordinary question. How quiet will the room be when nothing is happening? And when something breaks at six in the morning before a live show, can anyone find the right cable quickly?
This article takes them in that order. It is not a design manual, only a reading aid for the notes that sit beside a studio plan, so that you can ask better questions before work begins.
Noise criteria: a number for how quiet is quiet
A noise criteria rating, usually written NC followed by a number such as NC 25 or NC 35, describes the background sound in an empty room. It is measured across several pitches, because a low rumble from ventilation bothers a microphone differently from a high hiss. The lower the number, the quieter the room. A figure in the low twenties suits a voice-over booth, while somewhere in the thirties is common for a general production space.
The point is that the rating is a target agreed before building starts, not a promise you discover afterwards. It forces a conversation about air handling, lighting transformers, and the lift shaft next door, all of which add noise that no microphone technique can remove later.
If your plan states no target at all, that is worth raising. Without a number, nobody can say whether the finished room has met its brief.
- Lower number means a quieter empty room
- The target covers ventilation, mains hum and building noise
- Ask for the figure to be written into the plan
What drives the number up
Most studios miss their target for dull reasons. Air conditioning is the usual culprit: ducts sized too small push air faster, and fast air is loud air. Dimmer packs and power supplies near microphone lines add buzz. A wall that stops short of the ceiling slab lets corridor chatter straight through.
Some of these are cheap to fix on paper and expensive once plaster is up. Larger, slower ducts cost little at the drawing stage. Moving a dimmer rack to another room later means new cable runs, new containment and a delay to your schedule.
In small production spaces, the compromise is often between airflow and silence during recording. A common answer is to let the ventilation run between takes and settle it for the take itself, but that only works if the plan allows for a controllable system in the first place.
The cable schedule: a list that saves a bad morning
A cable schedule is simply a table. Each row names one cable run: where it starts, where it ends, what it carries, its length and its label. Audio, video, intercom, network and power each appear, usually grouped by type. It is the least glamorous page in a studio file and the one crews thank you for during a fault.
Without it, tracing a dead camera feed means pulling floor panels and guessing. With it, you read the label, go to the patch point and test one known run. Callum's rule on shoots is that anything unlabelled on both ends is treated as unknown until proven otherwise, and the schedule is how a studio avoids unknowns.
It also shapes the build. Seeing every run listed shows where trays need to be wider, where audio and mains cross, and where spare capacity should be left for equipment you do not own yet.
- Each run: start, end, signal type, length, label
- Group by signal type to spot bad crossings
- Leave visible spare capacity for later additions
Questions worth asking when the plan arrives
You do not need to be an acoustician to review these two items sensibly. Start by asking what noise criteria target the room is designed to, and how and when it will be checked. A measurement taken before equipment is installed and again after is a reasonable expectation.
Then ask to see the cable schedule in draft form. Check that the labels follow a pattern a new crew member could learn in an afternoon, and that the schedule matches the drawing. A mismatch between the two usually means one of them was never finished.
Finally, ask who keeps the schedule up to date after handover. Studios change. A new camera position adds a run, and if nobody records it, the schedule slowly becomes fiction. Naming one person to own it costs nothing and keeps the document useful for years.
Putting it to use this season
Autumn is when many teams review rooms before winter schedules fill. It is a sensible moment to check that an existing studio still matches its paperwork. Walk the room with the cable schedule in hand and pick five runs at random. If you can find all five and the labels agree, the document is in good shape.
Then listen. Switch everything off except the ventilation, stand where the presenter would stand, and note what you hear. A steady hiss, a tonal hum or a rattle each points to a different cause, and describing it plainly helps whoever you call for advice.
Neither check needs instruments, only ten minutes and attention. What you learn will make the next conversation about a refit or a new space far more specific than a general wish for a better room.
Noise criteria and cable schedules are not jargon for its own sake. One tells you how quiet the room should be, the other tells you where every signal goes. Ask for both in writing, keep them current, and a studio becomes easier to run and easier to repair. If you would like a second pair of eyes on a plan or an existing room, get in touch through the contact page and we will talk it through.
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