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 two in the recording studio design process

so you’ve convinced yourself (and maybe your investors) that you want to build your professional recording studio. the next step is to work through the design details. these include documenting your environment, your space, and how you want to use it. i have a simple checklist on my site to use as a guide for capturing things of interest:

– noise levels

– neighbors

– details of existing construction (if any)

– dimensions

– key requirements

get yourself a sound level meter (Radio Shack™ has a nice digital one that’s inexpensive) and a notepad. make measurements over the course of several days and mark it down in your notepad. does the AM/PM rush hour, or trucks, trains, planes create high levels of noise and vibration? when? does that impact hammer test center next to the automotive crash lab make too much noise for your acoustic violin recordings? (see my blob on site selection) all the noise and neighbor factors will weigh in later when determining what you need to do for isolation.

next, take photos of the site showing any existing construction and important features. a good starting point is at least one photo per wall, plus some of the floor and ceiling. not only is this good for your scrap-book, but later if you need help from a designer or on the forums, people will need to see how things are built in order to provide good answers.

now its time to get out your measuring tape and a large grid-lined paper (easily obtained in many art supply or office supply stores) and start drawing out your space. make the dimensions (as notes, or if inclined to the grid) as accurate as possible (1/4″ is good for imperial, 5mm is close enough for metric). make sure you include all dimensions so you can fully calculate the length of a given wall based on all the individual measurements (i find many people include 2 or 3 dimensions when they needed 3 or 4…). include water pipes, ducts, windows, doors, beams, fire pipes, utility equipment, stairs, odd protrusions, etc. remember to include the height of the room and when it varies from a single height.

you might need a couple of pieces of paper – one per room if needed but remember to create a single drawing with the overall floor plan so its possible to recreate the layout later…

finally, document your key requirements – need control room, need live room, need 2 isolation booths, need to move in and out 11′ grand pianos, need a lounge, restroom, etc… these bits of information all play into the design because you don’t want to build something that results in a crew of people trying to carry large equipment through your control room… then again, if your space is mostly control room with a booth, you probably want access to the control room without having to go through the booth so you don’t disturb the artist at work in the event someone has to come in or out…

if this is a commercial facility (be honest) then you need to follow accessibility regulations – this means access for people with various handicaps – and yes – it will likely cost you more to build – but it will cost you way more to get sued or censured with fines. you also need to make sure proper safety, security, licensing, etc all in compliance with commercial facility regulations.


so now you have the noise, neighbors, site, dimensions, and requirements all in hand. armed with this information it becomes possible to begin formulating the first design – either with a designer or as part of your own efforts.

next week we’ll start to work through some methods of bringing this information into play with a series of design attempts.

Recording Studio Design Guidelines

wow, this is tough because it really comes down to understanding what you are trying to do, your budget, and the location of your new studio. it really is a pain to hear “it all depends” but it does… it’s nice to dream about but in order to make it happen you need to get organized. there are a lot of Internet and book based resources for compiling a set of guidelines for your studio design, but in the end, there are a few key questions to answer to shape your design.

assuming you found the right location, then here’s a few guidelines to consider:

– isolation does make a difference — most people assume they can get by on little or no isolation, and in rare cases that is true, for most of us, getting a good level of isolation is going to keep things more organized in terms of odd sounds entering our recordings, or having disruptions because of neighbors concerned about noise levels. either one is distracting and can throw off those most excellent moments…

– good acoustics is essential — you need it, you want it, yes, really. always start with broadband bass treatments. this way, if somehow those treatments result in enough low, mid, and high frequency control, you’re done. nothing worse than starting with high frequency absorption and finding mud, then trying to correct for the mud, only to find you’ve taken every bit of life out the room. if the low frequency trapping is too much for the mids and highs – add some panels, slats, etc to get some of that life back – your recordings will love you for it.

– visibility is important — people like to communicate with one another directly – not through video and talk backs – try to get as much glass as you can into your walls so people can see it other. if you can make that glass open, then they can talk to each other and hear each others instruments, and generally bring life into your sessions that are just not nearly as fun as face-to-face productions.

– good vibes — no one likes to play in a dungeon (well, not many :-)) so good aesthetics do play a role. if you are running a commercial facility its important to consider flexibility in the aesthetics so they can be adjusted to accommodate the mood of the client and the session in general.

– ease of use — make it easy to get set up, rehearse, record, mix, party (if allowed ;-)) so consider layout carefully, try to design it so people can move large or heavy equipment in and out without risking damage to other equipment or people (do you really want someone carrying that B-3 in its road case over your new SSL console?) if you know you’re going to have long sessions – plan on a lounge with bathroom, kitchen, and some recreation. make sure that lounge is isolated from the recording space to avoid things like loud shrieks from the winners at the pool table from disrupting the 12th vocal take…

so that’s my short list – isolation, acoustics, visibility, aesthetics, and ease of use. there more technical details like electric, security, and so on but from a guideline view these are the main ones to think a lot about.