How much soundproofing do I need for a room

I’ve recently been ask “Would you know what the Db level requirement would be for an edit room?

This question could equally be taken for a meeting room or an executive office.

Technically speaking we’d make a room perform to a written specification known as the Noise Criterion (NC) or Noise rating Curve (NR) This takes any subjectivity out of the final hand over of any room, as a proof of design can be made by a simple measurement of noise across a frequency range of 63Hz to 6.3KHz with-in the room.

In terms of a non critical listening edit room a NC value of between NC25 and NC30 is adequate quality, where there is a trade-off on cost of building works and the lower you go in NC curve level, pragmatically you’d always building something with as quiet as system as possible.

What is stopping me getting a perfectly quiet edit room?

For example if each room is going to have a local split A/C fan unit installed this item will affect the background noise level the most. (Typical indoor units run around 29/36dBA) As long as nothing else in the room or outside the room constantly makes a noise louder than this air conditioning unit, then this unit alone will be as good a noise response level you will get out of a room.

How much will another rooms noise effect the design.

One of the most important design criteria is to isolate noise from adjacent rooms, The main point being that a normal sound track for a movie can have loud passages of sound at 95dBA (peaking at 102dBA) while a room may only block out 30dBA of sound and thus the next door room would hear 60dBA of the other rooms sound. (a lot!) Ideally the numbers need to be reversed where a specific sound isolating room wall will but block out 65dBA of sound. The usual problem in this type of design is restricting sounds from entering doors which in cutting rooms (I imagine at low cost) won’t be fully isolated acoustic treated doors.

How do rooms with sound proofing general fit in the NC scale?

Below is a simple list of Noise Criterion as they relate to rooms specification, while there is always a sweet spot between, cost, quality, and performance. It should be noted requesting the incorrect NC level especially when it is too low will seriously affect the style and cost of a build, where difference in true performance may only be noticed in .01% of the hours the room is used over a lifetime.

NC-15 NC-20 (the gold standard) Sound mixing and recording rooms, Concert halls, opera houses, broadcast and recording studios, large auditoriums, Large churches and recital halls

NC-20 to NC-25 Sound layback rooms, Small auditoriums, theaters, music practice rooms, large meeting rooms, tele-conference rooms, executive offices, small churches and courtrooms, private home countryside

NC-25 to NC-30 Edit rooms, Bedrooms, sleeping quarters, hospitals, Apartments, hotels and motels, private home urban

NC-30 to NC-35 Private offices, small conference rooms, Classrooms and libraries, hospital wards, corridors

NC-35 to NC-40 Large offices, reception areas, retail shops Cafeterias, restaurants, gymnasiums

NC-40 to NC-45  Lobbies, drafting and engineering rooms secretarial areas, maintenance shops,

NC-45 to NC-55 Kitchens, laundry facilities, computer equipment rooms, sports hall, factories.