Nothing kills a video like poor audio quality. No amount of set design, camera effects, or lighting tricks will help your finished video if your audio sounds like an old cassette tape. Beyond seeming unprofessional, poor audio quality makes it difficult for your viewers to understand the video. Your point gets lost in the static along with your voice.
Of course, some types of videos are less driven by audio than others. I can think of a few excellent videos that don’t have any speaking parts at all! But for anything with a voice over, on-screen dialog, or interview, you’ll want to make sure the sound quality is as good as possible.
Before we talk about how to prepare your own room, let’s take a quick look at how sound works in the first place. Once we understand what makes a voice recording echo-y or scratchy, we can start fixing the problem.
The Science Behind Sound
Sound moves in waves. When those waves hit something (like a wall), they bounce back. If you’re in a room with more than one wall (and let’s be honest, that’s most rooms), the sound wave will bounce back and forth. Over and over again. As you might imagine, sound bouncing back and forth across a room doesn’t make for the highest quality audio.
To give you a better visual of what this means, I’m going to turn it over to John Calder of Acoustic Geometry.
Like John says in the video, there are two types of sound in a room: direct and reflected. Direct sound comes from sound waves going directly to your ears (or voice recorder). On the flip side, reflected sound is created by sound waves bouncing off walls. Because reflected sound arrives at our ears later, it causes distortion. Basically, it makes audio sound bad.
To fix this problem, we have two options: absorb the reflected waves or diffuse them. Absorbing sound waves reduce the strength of the reflection. Absorbing all the errant sound waves may seem like a good a idea, but if you absorb too much, your recording will start to feel unnatural or lifeless. That’s where diffusion comes into play. Diffusion is just another word for scattering; sending reflected waves in different directions has a smoothing effect. To get the best overall audio, use absorption and diffusion together.
Common Misconceptions about Soundproofing
Up until this point, we’ve been discussing how to make the audio inside a room sound better. Absorption and diffusion only help with echoes, dampening the noise within a space. Although many people refer to this process as soundproofing, what we’ve actually been discussing is acoustics. Soundproofing, on the other hand, is how you block outside noise from entering the room in the first place. And it takes different tools to do both jobs.
Dampening sound within a room
Soft materials absorb sound waves better than hard materials (that’s why it echoes more when you walk on hardwood floors than carpeting), and surfaces with lots of angles diffuse sound waves. Put those two concepts together and it becomes pretty obvious why most recording studios are covered in soft foam with lots of angles.
Here you can see TechSmith’s recording studio; we used a combination of a few different types of foam to get the best overall audio experience.
Blocking external noise from entering a room
To soundproof, you have to stop sound waves from entering a room. Generally, very dense materials are good at this. Usually soundproofing is taken care of during construction because it can be difficult to reinforce a room after it’s finished. But don’t worry yet, there are a few tricks you can use to get around this setback!
Things to Try
For a truly masterful voice over, you’ll want to control for everything we’ve covered above: blocking outside noise, absorbing stray sound waves, and diffusing the rest. You’ll also want to use a professional microphone to pick up the best audio possible (Check out this blog about picking a microphone if you need help).
To block noise from entering a room, you need thick walls made out of a dense material. Think plaster instead of drywall. Since full-on construction isn’t exactly inexpensive, let’s focus on picking the best room you already have access to.
Choose somewhere remote, preferably without windows. The best spaces can seem unconventional: don’t count out closets, storage rooms, or even your car. Most cars built these days have built in soundproofing to minimize road noise. Use this to your advantage! No one will know if you record your voice overs from the passenger seat.
Recording in a busy office can be a challenge, but if you can’t find somewhere quiet, you can always send a polite email reminder to your coworkers when you need to record something, or let them know in-person.
Next, assess how much extra noise you’re still hearing. The easiest way to do this is to plug headphones into your mic and listen closely for anything it’s picking up. Is a dog barking? Do you hear construction noise? Maybe the fan in your desktop is whirring?
You’ll want to dampen any extra noise you hear: the goal is complete silence. You could buy acoustic foam and plaster it up in the room you’re using, but that’s not always necessary. Remember, any soft material can deaden noise. If you’re short on budget, try putting a blanket over your head and microphone. Sure, it looks a little silly, but it works! Hanging heavy curtains or carpeting on the walls of your room is another option.
Small spaces tend not to need as much diffusion as larger spaces, but if your audio plays back sounding dull, throw some corners into your room. Again, acoustic panels work well, but anything with some angles on it will do.
And there you have it—everything you need to know to keep those vocals sounding fresh! Have any tips I didn’t cover? Let me know in the comments!