Voice Over Audio Production Techniques
Professional's Guide to Voice Acting

Mixing and mastering refers to the process of enhancing your audio’s sound quality using EQ, compression, and gain, so that the audio remains consistent from track to track. Mixing and mastering also make it possible for you to offer the file to the largest audience possible in a format that’s accessible on nearly any device.

Mixing and Mastering Your Audio

When editing your audio tracks, it is a good rule of thumb to decrease rather than increase your frequencies wherever possible. Decreasing undesired sounds is always the less obtrusive option, since increasing too much can make a track too loud and lead to digital distortion when encoding the file.

Use Compressors to Reduce the Dynamic Range

A compressor’s basic function is to reduce an audio recording’s dynamic range, which is the difference between the recording’s loudest and softest sounds.

By reducing the volume of the loudest sounds, with a compressor you can raise the level of the entire audio track, causing the track to sound louder than it actually is. Compression can be a considerable help when it comes to making your audio tracks sound intelligible and maintain consistent volume. It is required for your audio track to sound great no matter what stereo system you play it on.

A compressor consists of a level detector that measures the incoming signal, and an amplifier that controls the gain by the level detector.

A Threshold control sets the level at which compression begins. Below the Threshold, the compressor acts like a straight piece of wire. But when the input level reaches the Threshold, then the compressor begins reducing its output level by an amount determined by the Ratio control.

The Ratio control establishes the proportion of change between the input and output levels. If you set the compression Ratio to 2:1, then when the input signal gets twice as loud, the output signal will only increase by half.

If you set the Ratio to its maximum (10:1 or more), the compressor becomes a ‘limiter’ that locks the maximum level at the Threshold.

While a compressor can level out a recording, high levels of compression can also introduce artifacts including ‘pumping,’ in which there is an audible up and down change in the volume of a track, or ‘breathing,’ which sounds like someone breathing as the background noise level goes up and down.

Expanders Increase the Dynamic Range

An expander is the opposite of a compressor. As the level of the audio signal grows louder, the expander’s amplifier also turns up, making loud signals even louder. An expander can be used to reduce noise in a process called downward expansion. In this case, you set the Threshold just above the level of background noise. The expander then raises the volume of everything above the Threshold, but won’t change anything below it, thereby lowering the perceived background noise.

Normalization Evens Out the Loudness

Normalizing increases the audio file’s gain until its loudest point is at a maximum level. The overall signal level is now higher, which makes for clearer audio, giving the encoder more bits of data to work with and reducing encoding distortion.

Normalization should be used carefully because it increases the noise in addition to the audio signal. It should be your last step before encoding, and you may not need it at all.

Recording Your Slate

Slating a demo simply means stating your name at the beginning of a read.

As with every industry, standards change. You don’t need to use slating in the case of online marketplaces (in fact, we do not recommend it), because it’s become a redundant practice. The client typically has everything they need in front of them. Given this fact and taking company preferences into account using the online marketplace, many voice talent are now choosing to read the script without opening with a slate. This goes for generic demos as well. Even though they’re considerably short, slates do comprise time and can take away from the read.

When in doubt, follow the instructions of the client or casting director. If they require a slate, then submit a slate. If they specify that you simply read the copy, do just that.

Converting Your File

Being able to convert audio from any format into an mp3 is an important skill to have in this business.

Most demo hosting services on the web, including Voices.com, require demos to be uploaded in mp3 format. Because mp3s are heavily compressed, it stands as the best format for sending files over the internet, both by FTP services and email, since they are much smaller than WAV files and other digital formats.

However, due to the amount of compression inflicted upon mp3s, your previously perfect audio quality may end up sounding scratchy, distant, or muffled after it’s been converted to mp3 format. A little remixing may be required. In most cases, simply boosting the gain will do the trick. The important thing to remember is to boost the gain only after you’ve first converted your file to the mp3 format.

Whatever recording program you’re using, you should be presented with the option to save or export your recording as an mp3. If your only option is to export as a WAV file, that’s okay too.

You’ll just have to complete an extra step to convert the WAV file to an mp3 file. An easy way to do so is with iTunes.

Checking Your Mix To Review Your Recording

After you have mixed down your mp3, test if it sounds good on a variety of stereo systems, such as your computer speakers, headphones, portable stereo, or car stereo. If your mix translates well from system to system, you will know that you have created a quality recording that will be easy on the ears.

Structure for Saving Audio Files

Organize your audio recordings. You will ultimately save a lot of time by being organized right from the start. Create a file in your Documents folder with an easily recognizable title like ‘My Voice Overs.’ Inside your ‘My Voice Overs’ folder, create new folders for each client that you have, or will be working with. Having a defined structure for your client’s audio will not only keep you organized but it will help you plan your work in advance. When saving you work, export your voice over recording as an mp3 file.

Save the file as: ClientName_Project_Version_01.mp3

File Sizes

WAV or AIFF files are uncompressed pure audio in PC and Mac format. They are massive files with superior audio quality, and often happen to be what clients need their projects delivered in for the final product. Compressed audio, such as the mp3 or AAC audio formats, make it far easier to stay within bandwidth limits. Compressed audio is easy to upload to Voices.com, deliver via email, and share online.

To encode audio, you need to know the bitrates and sampler dates. 128 kbps and 44.1 kHz are ideal (44,100 is standard mp3).

A professional sample rate will be of a much higher kHz. The sample rate is a basic measure of how close the sound is to its original. The smoother and clearer the sound is, the higher the rate will be.

Applying a Rule of Thumb

The most widely used digital audio format is the mp3.

Default setting:

  • Mp3 file, stereo, encoded at 128 kbps as a minimum, but can go up to 320 kbps
  • Mp3 equation is: 1 minute of stereo digital audio, encoded at 128kbps = 1MB mp3 file
Key Points of Mixing and Mastering

Now you know how easy it is to make your recording sound exactly the way you envisioned it. After mixing and mastering your voice over, you will be rewarded with your very own demo-ready mp3 file.