VO Weekly Workflow – Distortion and What To Do About It

The term “distortion” crops up frequently when discussing audio from home voiceover studios. Distortion may be applied to a wide variety of recording steps, making it tricky to determine precisely what someone might be talking about. The effects of distortion can range from recordings sounding “not quite right” to a vocal track that sounds like a space alien has taken up residency in our booth.

What is “Distortion” in audio?
At the simplest level, when we refer to “distortion” in voiceover recordings it means that the sound captured differs from the signal that entered the microphone. Of course, GIGO (“Garbage In, Garbage Out”) applies here. If the recording space has poor acoustic characteristics, we position the microphone badly, or neglect to place ourselves properly in front of that microphone, then the captured signal will accurately reflect that. The unusable audio result is not “distortion.” The recording setup rendered what it was given.

I focus upon improving those three variables every time I work with someone. Assuming that you have followed best practices and minimized flaws in the recording space, the signal you create should be free of those issues. Make things sound as good as you possibly can before trying to record.

It can be challenging to find the words to describe distortion. I find that using clear adjectives can often help clarify the specific issues. When you listen back to the recording, is it garbled? Buzzy? Does is sound like it’s underwater? In a windstorm? Does it sound like an overproduced horror movie ghost voice (assuming that’s not the goal…)? Those descriptions will suggest where the problem might be living.

Where Distortion Happens
Distortion commonly occurs during the input stage. The input gain setting is the main tool we use to control this. That setting is typically adjusted through a knob or slider in our audio interface, though sometimes there’s a software control. Increasing or decreasing this variable changes the “Peak” measurement of our input – the height of the wave measured in decibels (dB). If that Peak goes above the maximum that the system can handle, bad things happen to our recordings. It cannot deal with too high of an input level, and the recorded result is obviously inferior to the original signal. Distorted input typically sounds very buzzy, inharmonic, and overmodulated.

Most voice actors have experienced this. If you have ever yelled into a microphone during a video game audition and found that the resulting waveform gets cut off at the top of the recording, you have heard what input distortion sounds like. This type of distortion cannot easily be fixed. Deamplifying it after the fact just makes the distortion sound quieter. It’s why I suggest aiming the loudest Peaks of our recording around -12 dB. That gives enough margin for error (technically “headroom”) if we get a little louder than we plan. But what happens if our input levels are well controlled and we are still getting distortion?

Other Ways to Distort Audio
The microphones we use for VO are sensitive instruments, designed to capture detail. It is possible to overwhelm the actual capsule that acts as the microphone’s ear. The capsule has a large diaphragm that reacts to changes of pressure. If the sound pressure reaches a certain level, that thin diaphragm is overwhelmed and no longer renders the sound accurately. Microphones all have an SPL (Sound Pressure Level) rating which indicate the loudest direct sound they can withstand. Since sound increases exponentially, getting too close to the microphone can drastically increase that pressure past an appropriate level, overdriving the capsule or even the circuitry inside the mic.

If you are still getting distortion even with moderate recording levels, this is likely the case. Adjustments to the audio after it’s recorded matters as well. If your audiobook mastering workflow drastically increases the overall loudness (RMS) of your recording, it can be distorting the peaks during that step. In many cases, the recording software does not handle those changes well. Any increase in RMS creates the same change to the Peaks. If excessive, that can make things sound “crunchy” even after it’s “fixed” with a Limiter. A more appropriate mastering approach would increase gain in moderate stages that do not damage the recordings. If your raw audio sounds good but your final audio sounds buzzy or overly crisp, that is usually a sign of this issue.

Preventing distortion in our audio remains a challenge in creating a solid workflow. We are tasked with capturing an instrument with a very wide dynamic range. What we do is difficult!

Have you tested your studio’s audio quality to make sure it meets professional standards? For a free review of your vocal recordings, please use the upload tool on my Audio Review page.

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