Tips for Designing Accessibility in Voice User Interfaces

illustration: wired.com

Technology is relying more and more on voice interfaces that don’t have a screen, display or tactile interface. As we learn to design for this paradigm, we must also figure out how it impacts people with disabilities.

This article is concerned with both one-turn and conversational voice user interfaces (VUI’s). Most interfaces that are referred to as conversational are probably of the one-turn variety. Cathy Pearl in Designing Voice User Interfaces defines conversational design to mean “thinking about an interaction with a VUI system beyond one turn.”

There are four umbrella categories of disabilities that we generally design for: Deaf and hard of hearing, cognitive impairments, physical disabilities, and blind and low vision. A few tips are listed below for each type.

Deaf or Hard of Hearing

People who are deaf or hard of hearing are impacted the greatest by shifting to a mode of communication that relies on voice and they will likely need multimodal interfaces.

• Allow volume control. A user must be able to turn the volume of a device both up and down. Users who are hard of hearing may need to turn devices up to hear and those with hearing assistive technology may need to turn it down.
• Provide alternatives to speech-only interactions (multimodal). Users who are deaf may not converse using speech directly. To include these users, provide a multimodal experience.
• Consider conventions of transmitting to hearing devices. Users who are hard of hearing may wear devices that can connect via Bluetooth, FM or other means. Connecting to their assistive technology may create desired experiences for everyone.

Cognitive Disabilities

Many cognitive disabilities affect areas of the brain that process voice interactions. This broad range of disabilities must be understood to create a great experience for everyone.

• Create a linear, time-efficient architecture. When architecting conversations, make it easy for the user to understand the navigation and not get lost or trapped. Architecture is perhaps more important in an invisible interface than in one that is graphical.
• Provide context. Build the lexicon for your conversation with the context in mind. Many terms can be ambiguous and confuse users, especially those with cognitive disabilities. Then, make sure to add context to conversation to make possible responses clear for the user.
• Normalize language. DO use literal language, short and simple sentences, and full-length words. DON’T use ambiguous language, sarcasm, technical terms, abbreviations and acronyms.
• Put important information first or last. Put the most often used choices at the beginning and allow a user to quickly answer, or put them at the end so the user doesn’t have to remember all the choices. Avoid long menu options and don’t combine multiple ideas into one question.

Note: Conversational interfaces have been extremely helpful for people with dyslexia, allowing the users to interact without written text.

Physical Disabilities

Some physical disabilities may make it difficult for users to speak clearly.

• Understand shaky and broken speech. This may be out of your control, but realize that many users with physical disabilities have shaky and broken speech — especially those whose primary language is different than the system.
• Provide alternatives to speech-only interactions. Similar to users who are deaf, a user who is unable to speak needs an alternative way to interact.
• Design appropriate pauses in listening. Allow a user to pause and gather thoughts when speaking. Don’t be hasty to reply and tell the user that the system does not understand.

Blind and Low Vision

• Create a time-efficient interaction. Just as we try to limit the number of clicks a user must take to complete an action, limit the amount of voice interaction needed.
• Keep messages short and allow interruptions. Don’t force a user to listen to long messages or lists of choices without a way to continue forward.
• Let users control the speech rate. “Many blind users of screen readers can listen to text as exceedingly fast speeds.” (Pearl, 2016) Designers should recognize this super power and design accordingly.
• Make it discoverable. Consider how the ability to speak with a device is conveyed. If it is expected that a user speaks to a device, make sure that user knows it exists and can open a dialog.

Summary

Voice user interface design is in its infancy for most of us but with a little work we can create great, inclusive experiences for all users. Every project is different and each tip in this article should be interpreted and researched further for your own application.