Setting up a home voiceover studio? As a voice actor, the room in which you record is the most important factor to consider. It is more critical than your mic, your interface, expensive preamps, your computer and software. If your sound is compromised before it even gets to your microphone no amount of expensive equipment is going to be able to make up for poor acoustics.
There are two areas that you need to consider that are often confused and misunderstood: soundproofing and sound treatment.
The best approach when treating a space is to use multiple treatments concurrently to attenuate frequencies across the spectrum as evenly as possible. This is never going to be perfect, and short of a physics degree experimentation is going to be your best method for treating your recording room.
We’ll go into more details below, but here is what you basically need to do:
- Start with your empty space.
- Put in the microphone and stand, your music stand and any other equipment that is necessary for you to record, then record a sample.
- Gradually bring in your treatment and sample as you go until you have a room that cuts down the reflections as evenly as possible across the frequency spectrum. Don’t be afraid to leave areas of wall exposed, the reflections off of these can serve to offset extreme low end absorption and can add some brightness back into your sound.
Let’s dive in!
What is soundproofing?
Soundproofing is the process of preventing sound from leaving or entering your recording space. This has nothing to do with optimizing the sound quality of your recording; rather it is a fundamental requirement before you even get started.
So how do you soundproof your space? It depends on many factors. As voice actors we rarely have to worry about sounds leaving our space as our voices tend not to carry to the same extent as loud music. So our main concern is to prevent sounds from coming in and interrupting us.
Where to record your audio
Most people's first space is going to be a corner of a room or a walk-in closet in their home, and while this may not always look professional, if done correctly can produce extremely usable results. As you progress you may decide to invest in a dedicated audio booth, or even better a build out of an existing space (more on this later).
A walk in closet or a small room is useful as you can treat the whole space with a relatively small amount of material. If recording in a larger space, say a bedroom, you may be using that room for other purposes which is a compromise. With a larger space comes a larger area to treat and shares a larger surface area with neighboring walls or the outside.
How to choose your recording space
If your living situation affords you the ability to pick from multiple spaces to record in, there are a few things to consider:
- Does the room share any walls with neighboring rooms that produce noise? Say, a kitchen that is used regularly or a bathroom?
- Are there household appliances or technology that create noise nearby, such as HVAC, noisy plumbing, elevators, garage doors, washing machines etc.?
- Does the room overlook an outside space that could create problems such as traffic, leaf blowers, neighbors etc.?
- Is there power and ventilation? (This is particularly relevant if you’re using a walk-in closet).
- Acoustically speaking, a square room is the least optimal shape, so if you have two similar rooms with different dimensions, choose the least square one.
How to soundproof your space
A lot depends on what you are trying to eliminate. If you live near a busy train line then you are going to have to spend an extraordinary amount of money (create multiple walls, float floors etc.) and even then it will not eliminate the sound entirely. If however you want to insulate against household noise, outside sounds such as leaf blowers etc... there are some more realistic things that you can do.
Mass is the name of the game here, even better is mass plus air. Allow me to explain further:
Sound is essentially energy and the higher the pitch the less energy that sound has. Therefore the higher the pitch, the easier it is to soundproof against. Think of a car blasting music, with the doors closed you hear just the bass and low end sounds thumping. The car is successfully blocking the higher frequencies but is not able to soundproof the lower and more energetic frequencies.
You will have the same issue with soundproofing your space.
Your soundproofing is only ever as good as it’s weakest point, so first you will need to make sure that your space is completely sealed starting with spaces around doors and windows that should be filled in. If the door is hollow you could try to fill it with sound insulating spray foam or replace it with a dense fire door. You can also add a sheet/s of soundproofing material that overlaps the frame when the door is closed.
If you seal the room so effectively that you are creating an airtight box, you will most certainly need to have a ventilation system to remove stale air and replace with fresh. The way to achieve this acoustically is to put the vent outlet in one part of the room and then pipe the stale/fresh air conduit around the room and then through the wall as far from the vent as possible. This serves to separate the end of the vent from the break in the wall and reduce that as a weak point where sound can leak in.
READ: “10 Questions Every New Voice Over Actor Must Ask”
Treating your walls
Adding another layer of plasterboard will help reduce upper mid and high frequencies (the thicker the better), but if you really want effective isolation you need to decouple an inner wall from the outer wall. This can be done with an entirely separate stud wall, unconnected to any other, or via resilient bars (R-bars) that screw to the outer wall and provide a surface for the inner wall to attach to. The air gap between either the stud wall or the R-bars offers decent isolation, and the decoupling of the walls reduces sound vibrating from one surface to another.
If this still doesn't do the job, adding multiple layers of different thickness plasterboard will further insulate the space. Floating floors and ceilings are also a consideration if this is where sound is leaking in.
Soundproofing is expensive, time consuming and it is difficult to predict its effectiveness. So choosing the correct space to start with, and/or being able to live with certain restrictions may save you a significant amount of time, money and headaches.
What is sound treatment?
Sound treatment deals with how the sound moves around within the room that you are recording in. When a sound is created it hits any surface in it’s path. This causes a reflection and the sound will continue bouncing off surfaces until it loses energy. These reflections interact with one another creating audible anomalies. Clap in an empty bedroom to hear some of these sounds in their most raw form. And as I mentioned in soundproofing, higher and lower frequencies behave differently.
For those of you who like statistics, the optimal reverberation time for speech is 0.2 of a second. (Don’t worry, you don’t need to know this to create a pleasant sounding space).
The approach that most people take is to buy a stack of acoustic foam such as Auralex (those square sheets made out of small foam pyramids/triangular prisms) to absorb reflections, and they stick it on every square inch of the space. While it immediately reduces a lot of audible reflections, it does so unevenly. As we mentioned before, different pitches have different amounts of energy. Acoustic foam is only really effective at reducing upper mid and higher pitched sounds. Therefore the higher pitched sounds are reduced but the lower frequencies are free to bounce around unimpeded creating an uneven and muddy or boxy sound where the low end dominates.
Middle and higher frequency reduction (attenuation)
This is relatively simple, you can hang heavy drapes or thick rugs on the wall, you can use specialized products such as acoustic foam, you can bring in soft furnishings such as pillows and cushions. You can even hang thick clothing on hangers in various places around the space. If you’re feeling particularly handy you can construct your own acoustic panels. Check out this video from VO Tech Guru Tim Tippets who shows you how to do it:
Low frequencies
Reducing low frequencies is tough, they tend to form what’s called ‘standing waves’. They can bounce off surfaces and react with each other causing some frequencies to be exaggerated and others to be reduced and on occasion even eliminated—it’s very complicated! (Google ‘phase cancellation’ if you’d like a headache).
But there are some things that you can do. Thankfully the human voice tends not to produce significant low frequencies at high volume, so the effect is not so pronounced, as it would be for mixing music for example. Even in voiceover low frequencies tend to build up in corners, so adding mass there can help to reduce them in the whole room. One simple and cost effective way that I have found is to put a tall, thin book shelf across the corner(s) and fill it with books and magazines. This both cuts off the corner of the room and also fills it with very dense material that soaks up the low end. You can also buy specific acoustic products called bass traps that stick to the wall or stand freely in the corner.
Diffusion
Another way to reduce reflections is to diffuse them. Rather than absorbing sound, diffusers scatter sound waves. They should be placed directly opposite the source (your mouth in our case) to stop the sound from bouncing back at you and around the room. The problem with diffusers is that you have to be at least two times the wavelength away from them for them to be effective. 100 hertz has a wavelength of around 3.5 meters (11 feet) so for them to scatter sound effectively in the lowest register of a deep voice you would have to be standing a long way from one (over 20 feet!). The human voice does not produce volume levels (a.k.a. sound pressure levels, or SPL) to really justify that kind of treatment. It’s also extremely unlikely you will be in a room that large.
That was a lot of information, but acoustics are vitally important for your recording environment and you must become familiar with the relevant facts. A lot of information that you can find online tends to be tailored toward recording studios and music production (amplified sound amplifies the issues). While a lot of it does translate to VO, we only really need to be aware of the issues discussed above. At least to start with. You can go and have a lie down now.
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