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Acoustic Treatment Basics for Voice Over Studios

June 21, 2019

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Acoustic Treatment Basics for Voice Over Studios

Acoustics is an enormously complex subject. It is physics after all.

To go into anything more than a very basic level for this article would be both prohibitively difficult to write (book-length) and ludicrously dense with formulas, graphs and specific scientific language. We’re not acousticians: which is an entire discipline in and of itself.

As such, for this guide, we will be focusing on the practicalities of acoustic treatment in a vocal booth and highlighting, in the simplest possible way, the acoustic principles behind these treatments. This should provide enough knowledge for anyone to set up a professional recording sounding environment.

To structure this article in a more relatable way, we put out a request through Voquent’s social media pages for pictures of our voice artists’ own recording studios.

Let me tell you now, there was a lot of variety! We had the ad hoc, with just a pile of laundry surrounding the microphone; the homemade, with duvets in strategic locations; to the full-scale studio environment. And everything in between!

Thanks so much to everyone for sharing their studio pictures with us, it was a genuine pleasure to look inside your booths! And a special thanks to those we’ve included in the article below.

First up, let’s go over some general acoustic principles, tips & tricks.

Acoustic principles

We’ve noticed that a lot of people seem to be under the impression that you need to create a completely dead room with absolutely no reflections. This is drastic overkill! You don’t need to create an anechoic chamber.

Anechoic chamber

You’d be surprised how many home studios look like this on the walls!

Audio and the human voice ALWAYS exist within a real physical space.

Incorporating some space into the recording, even if it is a ‘voice of God’ documentary narration, is vital for a quality and natural sound. This is even more important for listening environments if you are engaging in broadcast level mixing and editing.

Some of the previous articles we’ve posted on here have been more of a straightforward list of “what to buy”. Acoustic treatment is far too complicated and variable to have a simple list like in the microphones article.

The price of acoustic treatment can change drastically based on what you’ve already got to hand (i.e towels and duvets) and what you intend to buy. Pricing is also affected by whether you are going all out for sound-proofing or basic acoustic treatment. As such, we’ll categorize the options as:

  • LOW: less than £150 / €150 / $200
  • MID : less than £500 / €500 / $550
  • HIGH: more than £/€/$500

Anyway: to business! Let’s have a look at some home studio setups submitted by our wonderful community of voice actors.

Quick disclaimer: we haven’t actually heard any output from many of these studios, so inferences are based entirely on the photographs.

Harrison’s low-priced setup

This is about as homemade as you can get. And it’s perfectly fine.

A recording from this “room” will probably sound better than 75% of other half-done “home studio” environments that haven’t been treated properly.

Harrison's home studio setup

Ah, studios like this do bring back memories. It may not look the part but it does the job just fine.

A bundle of duvets is FAR preferable to a big empty square room with laminate floors and no furniture. Furthermore, duvets also provide some pretty decent sound absorption even when compared to some ‘professional’ (and expensive) sound-proofing options.

If you are recording in a hotel, or your house is near a fairly busy road, then an arrangement like this could be ideal.

Harrison also, very wisely, realized that the computer needs to be outside the duvet fort, otherwise the whir of the fan will be one of the loudest things on the recording.

You’d be surprised how many people bring the laptop in with them. There are a few recording environments mentioned in this article that are otherwise very high quality in terms of acoustic treatment, but they have their laptop or computer in the same room as the microphone!

However, there are a couple of major downsides to a set-up like this. The primary one being it will get incredibly warm in there very quickly.

For a duvet fort to be an effective acoustic treatment option, it needs to be covered all the way around. This will obviously make it stiflingly hot. It will also rustle with every single movement, meaning you really have to keep still. It’s not very suitable for long recordings.

Also, you can’t really show a studio like this to paying customers. Most Skype live direction is done by audio only, but if the client insists on video, they may not be very happy seeing the voice artist recording in a duvet fort rather than a proper studio (even though it’s totally fine).

This is certainly the cheapest of the lowest priced environments here and it should really be considered a stopgap until you can invest in some proper acoustic treatment that allows you to stand up and move around more freely (and more comfortably).

Squeakycheese Productions low > mid-priced environment

Here is another studio sent to us via Twitter that is a good example to talk about some other aspects of acoustic treatment, and to point out some potential issues.

Squeakycheese Productions acoustic treatment

There’s some great acoustic treatment going on here, but it is lacking in some areas.

This studio from Squeakycheese Productions has some great acoustic treatment.  They’ve used acoustic diffusion panels in key locations but not covered the entire wall.

It’s actually a complete waste of money covering the entire wall, since reflections that are hitting the diaphragm of the microphone off-axis (basically indirectly), will go through many other scattering and diffusion effects from other objects in the room before returning to the microphone. It’s only the direct lines at the level of the microphone that really need to be worried about, unless you are in an empty room, tiny little cubic room.

ALSO READ: 5 Tips for Perfect Microphone Technique

As mentioned in the previous section with Mike’s studio. The SE Reflexion Filter ( other brands are available) can be useful for preventing reflections and make the size of the room generally “smaller” sounding.

However, in this setup it’s open at the top and bottom, so there is a risk of direct on-axis reflections above and below the microphones. There is only very thin carpet below the microphones, and there is no picture of the ceiling, an area that is likely to have been neglected.

A few extra diffusion panels will easily fix this though, and it will definitely not require completely re-designing the studio!

One potential issue I have noticed is that the microphones appear to be positioned off-axis in relation to where the voice artist would sit. This could lead to problems. The microphone may end up being on-axis to the reflections from the floor and ceiling, along with other indirect reflections.  This is something that can easily be fixed by simply moving the microphone.

In terms of acoustic treatment materials, this could studio could realistically be considered a low-to-mid priced. The SE Reflexion Filter is probably the most expensive thing, particularly two of them, but the panels are not pricey and perfectly up to the job.

Mike’s mid-priced setup

This is good example of a largely homemade well-treated home studio, to show you that acoustic treatment for voice over doesn’t have to cost the earth.

Voice actor Mike’s homemade home studio acoustic treatment

Voice actor Mike’s homemade home studio acoustic treatment

Mike has used office dividers (which have a certain amount of acoustic treatment in them), covered them in duvets, then suspended one above them.

The use of duvets around the microphone and performer will absorb most reflections. The use of something that looks very much like the SE Reflexion Filter alongside this duvet based acoustic treatment ensures the microphone will sound great with very few reflections, but still natural.

Over-treatment, can make the room sound ‘artificially’ small – boxy and unpleasant. Every sound exists in a natural space, as I mentioned above, and you always want to try and preserve some amount of ‘room’ in any recording.

Every sound exists in a natural space.

One key thing Mike has done that many neglect is to acoustically treat the area above the microphone.

There are reflections from the floor and ceiling, just as there are from the walls. Leaving out the dampening above the microphone will make a Reflexion filter, and the acoustic treatment on the walls, largely redundant.

A job half done – in the case of acoustic treatment – is a job you might as well not have even started!

The floor can be trickier to treat. The best you can usually do is to reduce reflections somewhat rather than absorb the sound. Mike’s set-up is fine, because he has carpet.

This setup can be considered comfortably mid-priced, mainly due to the office dividers. Office dividers are quite pricey unless you find them in a skip or inherit them.

Joyce’s mid-priced studio

Joyce has a great studio with a room within a room. She’s covered the inside of the small squared off room with diffusion / dampening panels. This is good so far, but it gets even better when you realise she has specific corner bass traps too! Hooray!

Joyce home studio voice over environment

Corner diffusion! Huzzah!

Corners are bad for forming something called a standing wave at low frequencies. This can make the voice over recording muddier and less pleasing to the ear.

Having some specific wedge-shaped sound dampening panels in the corner will help, particularly in a small booth set-up like this.

However (why is there always a however?), every room is different, and every room will have different frequencies that they resonate at.

Think of the standing wave as the wavelength that “fills” the room. Say, for example that you have a room with a set of speakers at one end, and a flat wall opposite it.

Everything will reflect off that flat wall, but there will be one frequency (and it’s associated harmonics) that will perfectly fit the size of the room. These are the specific frequencies that need treating, and corners are notoriously bad for causing this problem.

A simple graphical representation of a standing wave

A simple graphical representation of a standing wave.

There are a variety of different types of bass trap made from different materials. Whether you get a porous or non-porous material may depend on the intensity of the standing wave in the room. You may notice in your searches that some bass traps are flat, and are intended to be placed diagonally across the corner, leaving an air gap to take advantage of the ‘quarter wavelength rule’. Thus enabling you to reduce low frequencies with large wavelengths by taking up less space. Ok that’s a ludicrously basic version of the facts but it’s a close enough description!

ALSO READ: Why Auditions are BAD for the Voice Over Industry

In any case, Joyce’s simple corner foam pads will work well for its purpose i.e. a small vocal booth where the standing waves are unlikely to be too disruptive based on the limited frequency range of a human voice.

One potential issue is the acoustic treatment on the wall opposite the booth in the picture. There are no pictures of this wall, so I cannot pass any specific judgement, but if the wall is flat and bare, then some of the good work of this booth will be undone with the reflections coming from directly behind the voice over artist / engineer.

Of course, some of the reflected frequencies will be absorbed by the body of the person sitting in front of the microphone but it is important to ensure that every key area of reflection is minimised.

Joyce’s setup is likely to be within the mid-priced range, although the quality of the corner bass traps seems quite high, and some brands can be expensive!

Aimee’s mid >high priced acoustic treatment

Aimee sent in this picture of her recently created vocal booth, with ingenious screen mirroring set-up. This set-up looks basically indistinguishable from most professional studios in terms of the acoustic treatment set-up.

Aimee's studio and acoustic treatment

This might look like a lot of diffusion pads. And that’s because it is. This is a great set up

As I mentioned above, the only time you need to have acoustic paneling/diffusion covering every square inch of wall is when you have a completely square recording room, which is the case here. Those panels are only about £1 each but getting hundreds will add up!

Creating a little booth and covering the interior of that with diffusers to prevent most unpleasant reflections is the perfect solution. There is one possible issue with this (the corners of the booth) which I will come to later.

Aimee’s booth also has a soundproofing element. It’s too complicated to explain exactly what happens, but having a room within a room can reduce the relative decibel level of the noise outside of the second room. This is because the sound wave is having to expend energy every time it hits new material. In this case: the wall of the booth; the air in the surrounding room; and then the wall of the surrounding room.

For sound waves: energy = amplitude = loudness

The sound wave expends energy by changing the state of the matter that it is vibrating in and the specific material itself, can reduce the loudness in both directions.

Please bear in mind that is a very simplistic explanation. As I said at the start: acoustics is science.

The foam panels on the walls behind the speakers in the listening environment are probably a bit overkill. It is much better to just place the speakers further away from the wall (there will be recommendations in the instruction manual for your speakers) and forgo that sort of diffusion behind the speakers. It would make more sense to have the diffusion panels on the wall opposite the speakers, behind the listener, to reduce reflections from there.

The reason to move the speakers away from the wall (similar to the reason to record further away from the microphone) is the boundary effect. Again this is complicated but basically it causes some sound waves to be obliterated through phase cancellation and some to be artificially boosted through similar phase properties. Suffice it to say:

Move the speakers away from the wall and put the diffusion behind your head.

This set-up is probably high-priced due to the construction of a room within a room and the copious amount of diffuser panels needed. If you’re crafty with DIY and can get some reclaimed wood, then you may be able to do this mid-priced but the cost will naturally shoot up if you need to hire joiner.

Mark’s swanky high-priced setup

Mark has an Esmono booth. I’m not sure of the exact specification of this particular booth, or how much it cost Mark (I’m not that nosey), but this one I found online costs almost £6,000. Which easily puts this setup in the high-price bracket!

Mark's voice over booth is by Esmono.

A swanky Esmono booth.

In terms of the sound isolation and internal acoustic treatment, this booth provides everything you need. It’s well treated, enabling the voice artist to stand further away from the microphone and project their voice without loads of unpleasant reflections. As previously mentioned, any reflections can make the recording sound boxy and it’s great not having to worry about that.

The only reasonable criticism I can make of Mark’s setup is the listening environment.

A cardinal rule has been broken.

Never ever put anything on top of your speakers.

The speakers generate sound waves in air by vibrating. That means they will vibrate whatever you put on top of them too, such as ornaments or plants, especially at higher loudness levels. I would also recommend some acoustic treatment in the form of diffusion, along with placing the speakers further away from the wall. These are simple fixes that will improve the listening experience.

It’s a great setup though and if you’ve got the cash and don’t want to go through the hassle of building an entire room within a room and calculating the acoustic specifications for the booth. You can’t really go wrong with these Esmono booths (other brands are also available).

So there you have it!

You’ve basically got three potential price points, but ALL of the studios here have something in common: they are all, to varying degrees, a room within a room. Even the duvet fort (which I love).

If you want to record voice over in a bigger room, then you will need to invest in sound proofing and acoustically treating the entire perimeter of that room – essentially by building a room within a room. This is obviously expensive and puts you in the realms of building an actual recording studio. Obviously a far bigger investment of time and energy.

Nevertheless, the broad acoustic principles still apply. Here’s a summary of the key points:

  • DO: create some sort of a room within a room
  • DO: be aware of reflections behind, above and below (as well as the more obvious ones)
  • DO: try and avoid recording in a completely empty square room – books and clothes are perfect acoustic dampeners!
  • DON’T: overdo it with foam diffusion pads – only use in particularly reflective areas
  • DON’T: spend a fortune if you can’t afford it. Just observe the basic principles of acoustics and you’ll be fine.


More useful articles by Alex:

Everything you need to deck out your home studio professionally, whatever your budget.