Using Effects Plugins to Create Character Voices: Robots, AI, and Androids

One of my favorite challenges when producing speculative fiction podcasts is dealing with non-human characters. This can vary from robots to aliens, androids to animals, and everything in between. While some of these characteristics can be dealt with in the acting, sometimes it requires additional processing to create convincing non-human characters. It is always important in an audio setting to differentiate who’s who, and this can be done in many ways. The acting and the panning are the simplest ways to make one character stand out from another but sometimes we also need to reach for the right tool to make the difference meaningful, especially when one actor is playing multiple characters in the story.

Robots, androids and AI are some of my favorite characters to produce, and they come up often in speculative fiction. There are a variety of audio effects that are useful in the creation of these characters and in this article I will cover a few of my favorite techniques for creating convincing voices. The first effect I reach for when working to create a synthetic sounding voice is the comb-filter (think C3PO). This simple technique gives the voice a synthetic feel, while retaining the clarity of the speech – and the plugin is available with most freeware and purchased Digital Audio Workstations (DAWs).

Comb Filtering

Comb filtering occurs when a signal is delayed and added to itself. This can often happen when using multiple microphones (set at different distances from the subject of the recording) and can cause problems with the audio quality. When this occurs the frequency display on your FFT (visual representation of the waveform) will show up looking like the teeth of a comb, hence the name (See Image 2). However, this layering of frequencies and the subsequent phase cancelation can be used as a powerful tool for creating non-human voices. Many DAWs will have a built-in, easy to use comb filter. If your DAW does not, you can achieve the same effect by duplicating the track and delaying the duplicate by a few milliseconds. Play around with different amounts of delay until you find something that suits your taste.  

Image 1) Vocal waveform before comb filter                                                                                       Image 2) Vocal waveform after comb filter

Another go-to effect for robot voices is the ring-modulator (I.E. the Daleks). The ring modulator is a tried and true effect for creating otherworldly voices but easily gets out of hand and needs to be treated gingerly, as not to be overdone. While using the ring-modulator is not my favorite technique because it has been overused in cinema, if it is the right tool for the job, then by all means use it.

Ring Modulators

Image 3) screenshot of a software interface for a ring modulator, highlighting the waveform function

A ring modulator combines both the waveform (in this case your voice) and a signal from an oscillator, typically a sine wave, but most ring mods will give you a choice of waveform (See Image 3). The output is both the sum and the difference of the combined frequencies, but contains neither of the original signals and tends to provide a robotic cadence to the original signal. It is easy for a ring modulator to go out of control, so alter your parameters with care and play around until you find something that fits your taste.

Text-to-Speech Applications

Another fun way of creating robot voices is to avoid the actor all together and actually use a robot voice. Most devices contain text-to-speech capabilities and these can give you the genuine robot feel, but it is important to keep in mind that they tend to be tinny and need to be equalized for clarity. There are several apps that come in handy for this technique and have a broad variety of voices, however the accents can be pretty bad and can sometimes sound like a parody of the desired accent. This is not my favorite tool but it can have its place, but keep in mind when dealing with this approach that you will not have much control over the inflection, and nothing can replace a good “human” actor. Text-to-speech apps are easy to come by, and often free, or even built into your word processors.

The aforementioned techniques will serve you well for synthetic characters but what about aliens? Since we don’t really know what aliens will sound like this can be a fun and interpretive process and the choices are endless as long as we stay within the human hearing range (20-20k Hz). But this is the subject for a future article. Of course, there are many other useful effects for creating synthetic character voices, and I encourage you to experiment with: pitch shifters, flangers, vocoders, etc. In the meantime have fun with Robot, AI, and Android voices.

Jean-Paul L. Garnier

Jean-Paul L. Garnier lives and writes in Joshua Tree, CA where he is the owner of Space Cowboy Books, a science fiction bookstore, independent publisher, and producer of Simultaneous Times podcast. In 2020 his first novella Garbage In, Gospel Out was released by Space Cowboy Books and in 2018 Traveling Shoes Press released Echo of Creation, a collection of his science fiction short stories. He has also released several collections of poetry: In Iudicio (Cholla Needles Press 2017), Future Anthropology (currently being translated into Portuguese), and Odes to Scientists (audiobook - Space Cowboy Books 2019). He is a two time Elgin Nominee and also appeared in the 2020 Dwarf Stars anthology. His new collection of SF poetry, Betelgeuse Dimming has just been released and is available as a free download audiobook / ebook at spacecowboybooks.bandcamp.com. He is also a regular contributor for Canada’s Warp Speed Odyssey blog. His short stories, poetry, and essays have appeared in many anthologies and webzines.