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Designing Usable Voice User Interfaces

Voice user interfaces (VUIs) are quickly becoming an integral part of our daily lives, and they are a major UI/UX design trend in 2018. Used in smartphones, smart home devices, and a whole range of other products, VUIs are changing how we interact with technology, enabling new user experiences that drive growth.

What is a voice user interface?

A voice user interface, often referred to simply as VUI, allows people to control computers and devices with their voice. The very first voice-controlled user interface, the Audrey system, was built by Bell Labs in 1952, over half a century before Siri and Alexa came onto the scene.

While Audrey wouldn’t be able to give you accurate weather information or order kitchen napkins for you from Amazon, it could recognize numbers spoken into an ordinary telephone. After all, Audrey’s name comes from its special power: Automatic Digit Recognition.

Fast forward to the early 2000s when interactive voice response (IVR) systems were becoming common. Primarily used as the first response part of customer support calls, IVRs were infamous for their obnoxious design and poor voice recognition accuracy. Still, they proved to be useful for many fairly advanced tasks, such as booking a flight or getting stock quotes.

Designing usable voice interface is ruled by 3 main principles.
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Thanks to recent breakthroughs in machine learning and voice recognition, we now have VUIs, such as Amazon’s Alexa, Microsoft’s Cortana, or Apple’s Siri, that can converse in real-time and answer questions such “Will it rain today?” or “What are my reminders this weekend?” or even “How much time is left on the pizza timer?”

What modern VUIs bring to the table is improved accessibility and the ability to remain fully human in our interactions with technology. Modern VUIs allow us to us to interact with them using language, the most sophisticated method of communication we know, which has many benefits but also creates plenty of problems for voice user interface designers to overcome.

Principles of designing voice user interfaces

Designing usable voice user interfaces is not an easy task, largely because there are not many established VUI design principles on which voice user interface designers could rely. Still, we can point out at least three important design principles that every VUI should obey.

Simplicity trumps complexity

Human conversations may seem complex, but that’s only because they are full of repetition and redundancy. We are especially terrible at remembering a lot of new information at once, and many people struggle to remember even a single name without hearing it over and over again.

While it might feel tempting to design VUIs that mimic real human conversations as closely as possible, the goal should be to reduce complexity as much as possible and put meaningful information front and center in every interaction. This doesn’t mean that VUIs shouldn’t be personalized, but it means that personalization shouldn’t be the top priority.

“Do we want a personality to talk to or do we want a utility to give us information? I think in a lot of cases we want a utility to give us information,” argues John Jones, SVP Design Strategy at Fjord.

Encourage dialogue

Human conversations have a certain flow to them. They are not simply a series of questions and answers. Instead, they often start with a simple question and gradually develop as more information is provided.

A usable VUI must take into account context and be able to refer to past answers. The most advanced VUIs today, such as Amazon’s Alexa or Apple’s Siri, can already hold a dialogue to a certain degree, but there’s still a long way to go for them to be perfect.

There are at least 3 important things you must keep in mind when designing usable voice interface.
Image source

For instance, no VUI today accounts for the user’s current emotional state. This means that VUIs provide the same answer regardless of whether the user is angry, confused, joyful, or indifferent.

A VUI capable of recognizing various emotional states could, for example, ask an additional question to verify the answer of an apparently puzzled user or skip certain steps when conversing with someone who is annoyed.

Provide feedback

“One of the most common and noticeable mistakes made in conversational interfaces is to leave a user waiting without providing any feedback,” writes Nick Babich, editor-in-chief of UX Planet.

“In traditional GUI interfaces, users have the patience for only a few seconds before they think something is wrong. But the situation is much worse in the context of the voice interface, where users don’t have any visual feedback.”

Chatbots solve the issue by displaying various typing indicators, and some products that rely on a VUI do the same. For example, the Amazon Echo smart speaker indicated its state with LEDs. Ideally, voice user interface designers should provide feedback without relying on visual indicators. A message like, “Let me think for a moment,” is a good start, but using the same message every time isn’t ideal.

Conclusion

Designing great voice user interfaces isn’t easy, but there are some basic principles we can rely on to guide us along the way. Voice user interface designers who are not afraid to venture into an uncharted territory have the opportunity to test and validate their own voice user interface design principles and set the stage for the future.

Matt Warcholinski

Matt Warcholinski is the COO of Brainhub (a software house building awesome node.js web and mobile apps) who loves to build startups and play guitar.

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