How to Sound Design for People With Disabilities

Sound design for people with disabilities comes down to one habit: give every important sound a second way to be noticed, and let people shape the mix. The audience is large. The World Health Organization says over 5 percent of the world's population, about 430 million people, need rehabilitation for disabling hearing loss. It projects that nearly 2.5 billion people will have some degree of hearing loss by 2050. Blind and low-vision listeners, and people who find sound overwhelming, add to that number.

Different people need different things, so this guide goes group by group, with checks you can run today. Interactive music needs extra care because it often carries information. A new layer can mean an enemy is near.

Start with the mute test

The Game Accessibility Guidelines define essential information as "something you absolutely can't play the game without." Relying on sound alone is a barrier for people with hearing loss. It also fails anyone in a noisy room, on poor speakers or with the sound off to avoid waking a baby. Their test is simple: "ask someone to play through for the first time with the sound muted." If the person gets stuck, the information needs another channel, "usually visually, through an icon, effect, text, or other visual device."

Music is easy to forget in this test. A 2021 paper on adaptive audio describes Portal 2 adding a music track when the player nears an interactive object, and Crypt of the NecroDancer adding a shopkeeper's voice to the level music as the player approaches. Layers like these carry information. Where yours do, add a second signal.

Deaf and hard-of-hearing listeners

Hearing varies from person to person. Microsoft's gaming accessibility training notes that some players have trouble with certain frequencies, volume levels or sounds from certain locations, and that scenes with music, dialogue, effects and chat all at once can make the important channel hard to pick out. Subtitles for all important speech come first. After that, five checks help.

• Separate sliders. Give music, speech and effects their own volume and a mute for each. Accessibility and adaptive music goes deeper on listener control.
• A mono option. The guidelines explain that unilateral deafness can mean missing "important sounds that occur only from one direction," and a mono toggle plays the combined signal through both sides. Fold your own mix to mono and listen. If a part disappears, fix the mix.
• Captions for sounds that matter. Ask whether a sound "could be totally removed without much impact to story, gameplay or atmosphere." If not, add a caption or a visual. The guidelines report that 14 percent of The Last Door's players chose to finish the game with sound captions on.
• Speech clear of music. A mix that sounds balanced on your setup "will not necessarily be how players hear it," so keep important audio "as distinct as possible from any background audio."
• A number to aim at. W3C's Level AAA criterion for recordings that are mostly speech, such as a podcast, gives three ways to comply. One is background sounds at least 20 decibels lower than the speech, which W3C calls "approximately four times quieter," apart from occasional sounds of a second or two. It does not cover songs, but it is a fair target when music sits under a voice.

Blind and low-vision listeners

For someone who cannot see the screen, sound can be the interface. The Game Accessibility Guidelines say distinct sound design "can also be an extremely helpful reinforcement." They also note that "some games can even be playable by gamers who have little or no vision at all, if key sounds are all distinct." One caution: cues for every visual detail can be intrusive for sighted players, so make them an option. At the advanced end, their list includes an audio description track, a voiced GPS and a pingable, sonar-style audio map.

Forza Motorsport shows one way to do it. Engadget reported in April 2023 that Turn 10 Studios spent two years building its Blind Driving Assists with an accessibility consultant who is blind and other blind and low-vision players. A steering guide pans engine and tire sounds left or right to show which way to turn, and beeps warn when the car nears the track edge. Players can switch each set of cues on or off and change their pitch and volume. Engadget noted that it will likely take a while to get used to the cues, so plan for a learning curve.

Listeners who find sound overwhelming

For some people, sudden or constant sound hurts. The National Autistic Society describes hypersensitivity to sound this way: sounds "may seem much louder and sudden noises may be more distressing" than they are to other people. It says people with this sensitivity can become distressed by unexpected noises, or when their environment is too loud for too long. It also describes hyperacusis as everyday sounds seeming much louder than they should and sometimes causing pain.

Two rules follow. First, WCAG's Audio Control criterion (Level A) says that if audio on a web page plays automatically for more than 3 seconds, there must be a way to pause or stop it, or to control its volume independently of the system volume. W3C notes that sound distracts some people and interferes with screen readers. Second, in your own mix, avoid sudden loud stingers without warning, and offer a calm setting such as fewer layers, a fixed mix or no music.

Three extra checks for adaptive music

• Mirror the mood. If the music tells the player that danger has started, show it somewhere else too.
• Offer a steady mix. Let people hold the music at one layer, or switch off reactive changes.
• Never let music be the only warning. Put essential alerts in effects and visuals, and let the music carry atmosphere.

A 15-minute audit

• Play your build with the sound off. Note every place you get stuck.
• Play with only the music up, then only the effects. Can you still hear speech and warnings?
• Fold the mix to mono and listen again.
• Play on a phone speaker at low volume. Do the important cues survive?
• List every sound that carries information. Next to each, write its second signal. Empty cells are your to-do list.
• Ask a Deaf, hard-of-hearing, blind or sound-sensitive person to try it, early. Microsoft's training advises consulting "an array of players with hearing-related disabilities" because their experiences differ.

Accessible sound is not a separate version of your work. It is the same work with a second door. To go further on the music itself, read about spatial audio as an access feature and how stems give listeners control.

Sources

• Game Accessibility Guidelines: Full list
• Game Accessibility Guidelines: Ensure no essential information is conveyed by sounds alone
• Game Accessibility Guidelines: Provide captions or visuals for significant background sounds
• Game Accessibility Guidelines: Provide a stereo/mono toggle
• Game Accessibility Guidelines: Keep background noise to minimum during speech
• Game Accessibility Guidelines: Ensure sound / music choices for each key objects / events are distinct from each other
• Microsoft Learn: Audio accessibility fundamentals, from the Introduction to Gaming and Disability module
• W3C: Understanding Success Criterion 1.4.7, Low or No Background Audio (WCAG 2.2)
• W3C: Understanding Success Criterion 1.4.2, Audio Control (WCAG 2.2)
• World Health Organization: Deafness and hearing loss fact sheet
• National Autistic Society: Sensory differences, a guide for all audiences
• Engadget: Forza Motorsport will feature audio cues to help players with visual impairments drive (2023)
• SBGames 2021: A Tool to Implement Adaptive Audio Techniques on Unity Games (Rodrigues and Coutinho)