The project uses a custom LED matrix, shaped by cutting holes into a piece of cardboard. Gustafson then aligned the LEDs so they could support all of the mouth shapes to be used in the animation cycle. This project specifically is about creating a mouth, but it represents just one of many ways you could create a custom configuration of LEDs with Raspberry Pi.
Gustafson also created a program to accept audio input and output the appropriate mouth animation. To complete the process, he located a database of every English phoneme sound. Each sound had to be paired with a specific mouth shape to complete the animation. You can see his work in action, with the help of Avatar: The Last Airbender's Iroh:
The idea for this project is simple, but elements from its design can be used with plenty of other Pi projects. LEDs can be a really fun way to visualize audio. Why stop at illumination? You can use audio to trigger changes in color, brightness and more.
This project also demonstrates how easy it is to configure an LED matrix into custom shapes for a unique experience.
If you'd like to see more of this makers's work, be sure to follow Gustafson on YouTube.