Step Five: Isolation and Mode Analysis

So it’s been a while 🙂 now we are going to look at our room from the perspective of increasing the isolation and doing the initial mode analysis of our room.

From an isolation perspective we can do several things: one – increase the mass of the room boundaries – walls, floors, ceiling and windows and doors; two – seal everything really well – doors, windows, electrical and other boundary penetrations; and three – decouple noise and sound creating elements from the surrounding boundaries to reduce the amount of transfer directly through the structure. And in our example room we really cannot do much else if we’re renting (for example and very commonly asked about) or even if we own it, it might not be within our budget.

Adding mass to the walls and ceiling is pretty straightforward – we add some more drywall layers. if we choose this, we probably need to strip out the trim and outlets etc so we can add the drywall, and maybe it’s just a single 5/8″ (16mm) layer, and replace the outlets, switches, fixtures, trim etc. if we have access under the floor because it’s joist and subflooring – we can add layers of drywall between the joists (sometimes we line this with “blueboard” foam insulation to even it out because of nails) and seal it all up.

Remember – check with a properly licensed structural engineer before adding this extra weight to your building and of course obtain any necessary building permits and inspections needed to correctly complete this work, maintain your certificate of occupancy and your insurance coverage.

Increasing the mass on the windows and doors can take several forms but in our example we simply create a window plug to cover the window (like heavy indoor shutters) and seal up the doors. we could add a layer of MDF to the doors to increase their mass, and if they are hollow doors, replace them with solid core doors first. Increasing the weight of the doors means we need to also look at the structure around the door to make sure it is sturdy enough and also we may need to replace the hinges as well. we can make our own stops and seals or buy them from companies like Zero International.

E.g. Increasing our room isolation

Once we finish sealing everything, adding mass where we can, then we need to consider the air flow – in our example room we only have supply vent and no return as it’s a common return for the house. in this case assuming we need some isolation on the ducting, we can build an in-room plenum to isolate the supply from the rest of the house, perhaps big enough to slow the air speed down, and advantageously direct the air flow in the room. for the return, we could build an in room or in hallway plenum which vents into the common space so the return operates as expected. this return plenum could include a fan to ensure positive air flow out to the common area or it could be passive.

With isolation design out of the way (and please don’t consider this a trivial step – good isolation like anything else can be difficult to achieve when you have limited options and budget) the next step is to consider what we need to do about acoustic treatment design. the purpose of the design effort here is really to identify your main options for the acoustic treatments and get them incorporated into your budget and planning. what you will do is measure the room response after you complete the isolation work so you K NOW what you’re really into. plus the testing will also help identify any remaining defects in the isolation.

From a design perspective, we know that small rooms have a smaller number of modes which have enough space between them to be problematic and the proximity of surfaces causing interference and reflections on our mixing activity which often results in less than ideal translation on other systems. on the other hand we also need to consider the lack of room volume and our need for other considerations in the use of the room – maybe we record acoustic instruments, or someone in the home uses it for painting and bookkeeping. so we want to make some educated guesses as to how the room may respond and also what type of treatments we can add to fit our room requirements and budget.

With the room laid out in SU, it’s easy enough to download my mode template ( and scale it to fit the floor and two of the walls (long and short wall) and see not only the main axial modes but also first choice positions (like the 38% rule) so our subsequent design work can be checked.

E.g. Gullfo’s SU model template on the floor

With the main modes identified, we can also use several spreadsheet calculators (or Bob Gold’s online mode calculator) to verify our room characteristics such as tangential and oblique modes, first reflection points, etc. it can help to have some of the key equipment specifications handy when calculating reflections, lowest frequency response from your monitors, possible desk reflections, and speaker positioning etc.

E.g. Chris Whealy’s Control Room Calculator

Armed with this information, in the next post we’ll start to layout the room based on our assessment. we will start with standalone treatments which are typically commercial products such as those from GIK Acoustics or Real Traps, or they can be DIY treatments (we’ll start with POA (plain old absorbers) and think through more sophisticated units such as VPR or limp membrane absorbers). A subsequent post we’ll look at the use of integrated treatments and understand how they work together to go even further in shaping your room response.

Step three in the recording studio design process

Going green. It’s much more than money (assuming your currency of choice is green…). And in today’s constrained financial times, getting a budget and staying within the budget is more important than before. Once you are operational, you need to consider the day-to-day costs for the studio – electricity is the life blood of electronics and there are several aspects to consider.
Electricity is not free (unless you are one of the few people who are either producing it in a sustainable manner already or you have subsidies). The price you pay per unit of electricity is not the only cost to consider either. if you are not aware of the news regarding climate change and sustainability and carbon footprint etc. then you might want to look into these topics to better understand how your consumption of electricity flows in a cycle which impacts many places – from obtaining the fuels to run the power plant, power distribution, construction of the infrastructure that delivers it to you, and the radiation from your electronics which flows through you and your neighbors.
The construction of your studio needs to consider the sustainability angle as well as local requirements for use of building materials which may require permits or fees or additional inspections plus licensed or skilled installers. disposal of the construction waste should be performed in accordance with your local regulations as well as a clear conscience.
All of these details can impact your costs, timelines, and overall construction and working budgets.
Fortunately the Internet enables people to communicate more effectively than ever before and therefore finding the information you need about the rules for your studio and people with experience to do the work is easier than ever – but it is still work so don’t expect magic. that said, you are building something which many people will find desirable and unless you have the monetary backing, consider bartering the materials and work in exchange for time and output from your new studio. consider it “sweat equity”.
Using recycled materials can save much on costs especially if your new studio has a lot of finishing materials like flooring, slats, wood trim, etc. be aware that older materials could contain toxic or volatile materials or are not structurally up to specification, which you want to avoid for safety, health, and regulatory reasons. make sure you inspect (or have someone you trust inspect) the materials and verify their suitability for purpose.
Sometimes new is better as well. new insulation from recycled cotton products has both good acoustical properties as well as fire and insect / mold retardant – check your distributor. using paperless gypsum wall board saves paper and is generally better for environments where moisture could be an issue because it is less likely to promote mold growth. paperless GWB is more expensive in many markets so go with the type best suited for your budget and needs.
Lightweight steel framing is generally better for isolation walls than wood given similar construction and can lower the amount of lumber needed for framing (still best to frame out the doors and windows with wood or heavier grade steel). Using the steel framing can also cut the overall parts needed to obtain good isolation and the process of assembling it is generally understood by many carpenters.