A Comprehensive Guide to Voice User Interfaces (VUI)


Voice User Interface (VUI)

Remember using Apple’s virtual voice assistant, Siri, on the iPhone 4s when first launched in 2011? Wasn’t it an otherworldly kind of feeling? Since then, we’ve come a long way- Google Assistant, Amazon’s Alexa, Microsoft’s Cortona, and many more. And thinking about how famous voice-based AI has become, it is only significant to dive deeper into Voice User Interface (VUI) design and know more. 

As per Google, around 41% of individuals who have a smart speaker feel like speaking with another person or a friend. This makes one think, is Voice User Interface revolutionizing how humans interact with a device? The answer to this question will vary from person to person; however, before rushing to any conclusions, let’s first understand what exactly Voice User Interface is and how you can create VUIs.


What exactly is Voice User Interface (VUI)?

Voice User Interface is an interface that lets users interact with an app or a device via voice commands. With an increase in the use of mobile devices, visual fatigue has gone on to become a broadly experienced issue. That, in turn, has given more advantages for creating and using VUIs. Voice User Interfaces offer hands-free, total control on apps and devices, without the trouble of looking at a screen. Whether it is a voice-enabled mobile app, AI assistant, or voice-controlled devices such as smart speakers, VUI has become immensely common.

Tech giants like Amazon, Facebook, Apple, Microsoft, and Google have created or been creating their voice-controlled AI assistants. Besides AI assistants, smart devices offering voice user interfaces are also ruling the world, like Apple HomePod, Google Home, and Amazon Echo.  

Understanding the meaning of VUI is important to develop a UI/UX design that does not frustrate the users and offers a good user experience. So, now that you know what VUI is let’s look at the next crucial question, i.e., how to design an effective Voice User Interface?


Designing a Voice User Interface:

Designing a Voice User Interface isn’t very different from designing UX or any GUI project. Here is a breakdown of the VUI designing process:


Step 1: Do User Research

Start by understanding how users interact with AI-powered voice assistants in several engagement states with the help of the customer journey map. 

Concentrate on understanding the user’s motivations, behaviors, and needs. Include voice as an important channel in customer journey mapping to know where and how voice could be used for interacting. 

Highlight where the voice interactions could be integrated into user flow. That’s possible only when the map of your customer journey is still to be developed. If you already have the map ready, check if the voice interactions could enhance user flow.


Step 2: Conduct VUI Competitors Analysis

A VUI designer should do a VUI competitor analysis to check how the competitors are using voice interactions. Figure out the voice commands they use in their app, and analyze the feedback of their customers or users through the reviews.


Step 3: Know your User Requirements

Besides conducting user research as well as competitor analysis, try user testing and interviewing. It would help if you captured varied scenarios before using them as conversation flows. Utilize flow maps for noting down the user needs and make a dialog flow for each of these needs. Then, create a prototype of the conversations between the voice assistant and users.

How to create successful dialogue flows:

  • Make a solid error strategy
  • Keep the interactions simple and conversational
  • Have an added layer of security
  • Confirm when any task is done

A VUI designer should create the dialog flows as well as the whole conversation between users and the system. The dialog flows need to guide users successfully. 

A dialog flow should cover:

  • The main keywords for the interaction
  • Example dialogues for AI assistants and users
  • Branches where conversation can head to

You will find a dialog flow similar to a prototype covering the to-and-fro conversation. Luckily, several prototyping apps are available that ease the dialog flow creation process for Voice User Interface designers.

A few prototyping apps for VUI are:

  • Speechly: Language understanding tool for building VUIs.
  • Voiceflow: Collaboration app for designing, prototyping, and creating for Amazon Alexa and Google Assistant.
  • Dialogflow: A Google-owned tool to design a conversational UI for mobile apps, web apps, devices, and bots.

Amazon now offers a tool called ‘Alexa Skill Builder’ to help the VUI designers build new Alexa skills.


Step 4: Testing

It’s now time to refine or improvise what you have done so far. Test the dialog flow between the voice assistant and user. Keep in mind that you always have the option to head back and tweak your VUI specifications.


Step 5: Know the Anatomy of Voice Command

The voice command of a user consists of three crucial factors: Intent, Utterance, and Slot.

  • Intent refers to the objective of the voice command given by the user. The intent of voice interactions could be either high or low utility interaction. Low utility interactions are about performing difficult or vague tasks. For instance, if the user asks to provide more data about a certain topic, the Voice User Interface should check whether it falls under its service limit and then ask more questions for responding better. On the other hand, high utility interactions are specific tasks, like a user requesting the fan in the bedroom be switched off.
  • The utterance is how the user gives a voice command for triggering the task. A few phrases for request can be easy and simple to interpret, like ‘Play a track on Spotify,’ however, Voice User Interface designers should consider other kinds of variations too. For instance, instead of ‘Play….,’ a user could also say ‘Could you play…’ or ‘I want to listen….’
  • The slot is the optional or required variable requested from a user to complete the task. For instance, if the user says ‘Play soothing music,’ then ‘soothing’ is the variable here.



We hope that the blog helped clear your doubts about designing VUIs. With a rapidly digitized world, it will not be wrong to say that we may see Voice User Interface integrated into several more products in days to come. But will VUI eventually turn into a key medium of interaction? We shall see.   


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