Acoustic Treatment for Podcasters | Controlling Reverb
Room Verb. It’s the bane of any recording or listening environment.
It can mean the difference between a dry, professional recording and a hollow and incomprehensible interview. The difference between a clean mix and a muddled mess that doesn’t sound its best outside of the studio in which you mixed it.
Luckily, there are several tips and tricks to tame that recording environment to get a great sounding take whenever you press record.
Reflections, Flutters and Standing Waves
Reverb in a room is a result of reflections.
Sound travels from the source. The sound hits a wall or other surface and bounces back into your ears at a delay, causing a reverb or echo.
But unlike light, sound doesn’t travel along a single path. It resonates outward and bounces against many surfaces, simultaneously or in succession, leading to several reflections that define your acoustic space.
Additionally, the location and size of something reflecting your audio can cause a build up of certain frequencies.
Walk into any standard rectangular room without carpeting. Stand near a corner and clap your hands. Unless that room has been built to very specific acoustic dimensions, chances are you hear a slight warbling ring after you clap your hands. This ring is called flutter.
Now imaging your voice or your mix in this space, and you’ll begin to understand how that annoying little ring can produce less than optimal results when recording or mixing in that space.
Similarly, stand in a corner of the room and speak in a low natural voice. You’ll notice that your lower register resonates more. A boxy reflection occurs as your voice bounces not only off the corner walls and into you ears, but off the ceiling above and the floor below you. This produces a standing wave that unnaturally enhances the bass reflections in your room.
Absorbers and Diffusers
Fortunately for us, there are several ways to tame a room. And not all of them involve shelling out hundreds of dollars for Auralex products.
First, though, let’s talk about the differences between absorbers and diffusers and what each does to your room sound.
Any given surface in a room does one of three things to any sound that hits it: absorb, reflect, or diffuse.
In reality, all surfaces do all of these things to one degree or another, depending on the characteristics of the sound, but it it helps to understand it more simply.
The characteristic we're most trying to avoid in our space is reflection. Specifically direct reflections that are going to bounce of the walls and into your ears or microphone.
This means that we want to create a space that either absorbs or diffuses the sound in the room – without necessarily deadening the sound of the space being recorded in.
Solution 1: Gobos
A gobo (an industry name, short for “go between”) is mounted to a microphone stand to absorb sound behind the microphones and to the sides. They're also referred to as reflection shields.
Reflection shields work great in non-harsh acoustical environments that just need a little absorption to prevent echo. If you are recording in a well-fabriced bedroom or a clothes closet, this may be all you need.
In a pinch for cash? This video shows you how to make your own gobo on the cheap. I’ve built a few of these myself, and they work very well!
Solution 2: Sound Blankets
Sound blankets (AKA, Moving blankets) are a staple for controlling sound in film and audio recording locations. Be sure to get the quilted moving blankets, as they absorb sound much better.
I used some inexpensive shower rings to hold the sound blankets to the PVC and get solid professional results.
Solution 3: Absorbers
Looking around the internet, you might get the impression that Auralex has cornered the market on sound absorption materials. Thankfully (and less expensively) nothing can be further from the truth.
For a bit of the DIY treatment, some Owens-Corning 703 fiberboard wrapped in burlap, duckcloth or similar, has great absorption.
Or, as an alternative to Auralex, for you folks in the United States, I get my studio foam here.
Where to Hang Your Absorbers/Diffusers
Okay. So, you’ve got your absorbers and/or diffusers and you want to know where to put them. Here's two methods to get you going.
Method 1: There’s An App For That
Auralex has produced an app for both Android and iPhone that helps you map your recording space and shows you the optimal placement of absorbers and diffusers in your space. You can find those apps here. The original web-based version is also available here.
Method 2: The Mirror Test
The mirror test is a fairly simple means to determine where to hang your acoustic foam.
- Place your monitors (for a listening room) or a stationary object (for a vocal room) where the monitors or speaker will normally stand.
- Place a compact or hand mirror against each wall in the room, level with the monitors or object.
- Mark any spots along the wall where the monitors or object are visible from the mirror while standing directly in front of it, including the wall directly in front of and behind, as well as the ceiling.
- Install your foam and diffusers where you’ve marked using the mirror.
Really effective sound treatment doesn’t have to cost an arm and a leg. A little DIY and some diligent mirror work can save you a bundle on equipment and improve the sound of your recording or mixing space immeasurably. Your podcast listeners will notice the difference!
If you'd like some more tailored help with creating your recording environment and improving your audio quality, be sure to check out The Podcast Host Academy – that's where you'll find all our courses, community forums, and regular live Q&A sessions!