VO Studio Acoustics: Reflecting on Reflections in our Recordings

How do we learn to recognize good sound?

We’re surprisingly immune to noticing imperfections in our VO recordings – especially reflections or echoes. It is likely related to our social orientation, and the magic of learned language. In short, when people talk, we listen. We focus upon what is being said, and our brains do a wonderful job of filtering out those sounds which are not coming out of the speaker’s mouth.

Why We Don’t Hear Stuff

The more urgent and immediate the message, the less likely we are to notice “other” things.

This works really well for communicating. Though humans are basically a soft, fairly defenseless, tasty snack compared to most animals, we’ve done reasonably well as a species. Adaptation of verbal communication into language allowed the sharing of generational wisdom.

Our ability to selectively focus upon that verbal information increased as well, allowing us to filter out the extra noises and distractions with our brain.

Microphones Hear Everything

However, our microphone does not have a brain attached (well – so far…). When we place that simple transducer in a space, it records everything. People complain about microphones being sensitive, but that is their job. That is what they are supposed to do for us. We just get surprised by all that other stuff the microphone captures.

The biggest distraction is generally reflection. Sound is simply a change in pressure – a vibration of air. When we speak, we create that pressure change by pushing air through our vocal folds. It rushes out in a wave. When that wave hits something hard, the energy is bounced back. Just like waves in a pool or bathtub. The waves may come right back at us, or they may skip away like a rock on the surface of lake – heading into a direction we didn’t quite expect but continuing to carry the energy.

The words are the “direct” signal, straight from our mouth to the sensitive ear of the microphone. Any indirect waves come back to our microphone at different times – slightly after the words we spoke. If it takes a long time, we call it an echo – a distinct repeat of the sound after a period of time. It takes distance to make that occur. But when in a small room, the sound does not take that long getting back to us. These “short echoes” layer in with our direct sound. That impacts the clarity of our recording.

Acoustic Reflections Cause Problems

Those primary reflections of our voice actually change how we sound. When you combine a bunch of out of phase waves, they start to cancel each other out, meaning certain frequencies are reduced or eliminated. That’s why you can sound weirdly muffled or “thin” in a recording (assuming you are talking into the correct side of the microphone from an appropriate distance).

What stops the primary reflections is soft, appropriately dense, absorptive material. It makes the sound waves lose energy – just like the breakwater around a small boat harbor. If we’ve worked together, the first thing we likely addressed was locating all the hard surfaces in your space. In most cases, we find bare undersides of shelving, copy stands, hardwood floors, or other areas which negatively impact your sound.

But one area easy to overlook… (cue creepy horror movie voice) “there’s something behiiiiiiind you!”

Final Room Check: Turn Around 

Yep. That door, wall, or lack of wall matters. A lot. Whether it’s the unpadded door to your closet, or the big open room behind you, the area in back of you has a strong impact upon your sound. It’s easy to get focused on surfaces in front of you when you face the mic, but it’s important to take into account what is happening in the rest of your space. 

Since most VO mics have a cardioid pickup pattern, it mostly wants to “hear” the sound from behind you. When you turn around, you are looking at the reflection sources that the microphone is most likely to capture. Cover that stuff or add a PVC framed soft back wall. That’s much more important than even the ceiling in most recording spaces. 

This information recently went out to my email community. If you would like to join in, please take a moment to share your contact information through this sign up form. Thank you.