Playing by Ear: Using Audio to Create Blind-Accessible Games

Have you ever played a game with a configuration option to turn off the graphics? I'm not talking about an option to turn down the level of detail or switch off textures, but to turn off the graphics completely?

How many games have you played with options to turn off the sound?

Most people can't imagine playing a videogame with no graphics - even the name videogame indicates that they're a visual activity. At Zform, we've decided to be different from most game companies. We're developing games with parallel graphical and audio user interfaces (GUIs and AUIs). In our case, we're doing it because we want to bring the excitement of online multiplayer competition to visually impaired people around the world.

There are over 7 million people in the U.S. that can't see well enough to read this magazine article. Many millions more need to find their glasses to read it. The percentage of the population that has trouble seeing is getting larger every year as the baby-boom generation ages. If you'd like to sell your game to the largest possible number of people, you should think about using audio to reinforce the information you present graphically.

Another area where audio interfaces shine is on nontraditional gaming platforms such as mobile phones or PDAs. Perhaps the next blockbuster gaming platform will be audio-based games running on portable MP3 players. After all, MP3 players have all the requirements of a good gaming platform: lots of memory, a fast CPU, high-quality stereo sound, and several buttons for user input. The lack of a high-resolution color display shouldn't impede a creative game designer.

So what if you're not creating games for visually impaired players? Even if you are creating another first-person shooter with a target demographic of able-bodied 18-to-34-year-old males, you should still consider using audio for more than just gunshots, grunts, and death screams. No matter what type of game you are creating, paying careful attention to the audio user interface and 3D audio environment will enhance the player's experience.

Technology Platform

In this article, I'll be describing the techniques we use to create an audio user interface for a first-person 3D game we're developing. Our goal is to create an interesting, compelling 3D environment in which both blind and sighted players can compete as equals.

We decided to use the Quake 1 engine as our technology base, for several reasons. First of all, older technology is great because it runs great on older machines. Blind folks usually don't have the latest and greatest PCs with state-of-the-art sound and video cards. Our target system is a 200MHz Pentium with VGA graphics and any DirectX 7-compatible sound card. The second reason we chose Quake 1 is because it's open source. Kudos to id Software for making it available as a starting point for innovative projects. Finally, we have the source code. We knew that no matter what engine we chose, we'd have to make lots of modifications to the audio and navigation code to create a blind-accessible game.

All of our audio is created in 22kHz, 16-bit format and played back in stereo via DirectSound. We assume that our blind players can hear stereo sound (that they're not deaf in one or both ears).

2D Audio Interface
Our first task was to make all of the introductory menus and text both audible as well as graphical. A little bit of programming extended the menu and option GUI to play back arbitrary sound files, instead of making the generic Quake "clank" sound. It was simple to record somebody reading each of the menu entries so that each entry is identified aurally when selected. Some of the game options were trickier than others, such as entering an IP address to set up a multiplayer game, but none was too difficult.

One simple rule we followed that many other games do not was to make narrations interruptible. This was especially important for our audio menus; it's no fun to listen to six options play back when you know you want the seventh.

Speaking of narrations, another thing we did that was very effective was to use the game's main character voice for all of the game's menus. Our main character, Momo the monkey, has a distinct, silly accent. Using Momo's voice for the initial game-setup menus was a great way to introduce the player to Momo and to set the right mood for the rest of the game.