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Voice User Interface

1. What are Voice User Interfaces?

Voice user interfaces (VUIs) allow the users to communicate with a system through voice or speech commands. Virtual assistants like Google Assistant, Siri, and Alexa, are some examples of VUIs. The principal advantage of a VUI is that it allows hands-free and eyes-free experience in a way where the users can interact with a product while focusing their attention elsewhere. A voice command device (VCD) is a device that controls a voice user interface.

2. Where can we use Voice User Interface? What are its benefits?


  • iPhones, Pixels, Galaxies.
  • Connectivity — Cellular networks, wifi, paired devices.
  • Environmental context has a significant impact on voice interactivity.
  • Users are habitual to using voice interaction.
  • Allows interaction in visual, auditory, as well as tactile feedback.
  • Interaction methods are fairly regulated across models.


  • Use-case specific, like a watch, fitness band, or smart shoes
  • Connected with cellular networks, wifi, and paired devices.
  • Some wearables allow interaction through auditory, visual, and tactile feedback, though some are more passive and with no specific user interaction.
  • Typically is dependent on connected devices for user interaction and data consumption.

Stationary Connected Devices

  • Desktop computers, appliances with screens, thermostats, smart home hubs, sound systems, TVs.
  • Connected with Wired networks, wifi, paired devices.
  • Users are habitual to using these devices in the same location and settings on a habitual basis.
  • Quasi-standardized techniques of voice interaction with similar device genres like desktop computers vs. connected hubs and Google Home/Amazon’s Alexa vs. smart thermostats.
  • Non-Stationary computing devices.
  • Laptops, tablets, transponders, automobile infotainment systems.
  • Connected with wireless networks, wired networks, wifi, paired devices.
  • The primary input mode is typically not voice.
  • Environmental context has a significant impact on voice interactivity.
  • Typically have unstandardized voice interaction methods between device types.


3. What are the steps for designing a voice user interface?

(i). Research your audience

The basic aim is to gather information and understand the behavior and needs of the users since this information is what makes the foundation of the product requirements. Identify the pain points of the users and how their experiences are. By this, you will be able to monitor where the users can benefit. You must gather information in the user language - How they talk and the phrases they use. This will help you design a system accordingly.

(ii). Define

You need to determine the capabilities and shape the product accordingly.
This includes – Creating fundamental scenarios of interaction.
These scenarios come before the specific ideas of the app and should be identified to be turned into conversational dialogue flow. So, you need to design scenarios having high value for your users. At times, it can be confusing as to which scenarios are important and which can be overlooked.
For this purpose, you can use a use case matrix to monitor each one of them. Make sure these scenarios work with voice.

What matters the most here is that the users can solve a specific problem more efficiently than they would be able to with the alternatives. This step aims to find the common and specific cases which users will benefit from.

The three factors - Intent, Utterance, Slot.

Let’s understand these, with the example of  “Play some music”


It serves a broader purpose of the voice command.

There are two types of intents –

A. High utility (very particular and straightforward command)

B. Low utility (vaguer and hard to crack)


It looks at the likely ways the users can phrase the request. In our case, the option to “Play some music” could also be “I want to hear some music” or “can you play a song” and so on. All the UI/UX designers of VUI have to consider the variations.


When the intent is not enough, slots come into action. They refer to the extra information needed to achieve the most beneficial results for the query. In our example, the slot is ‘relaxing’ but it is optional as the category of music is not defined by the user. However, if the command were ‘book a taxi on Uber’ the slot would be ‘destination’, thus making the slot required and not optional.

(iii). Test your product

After everything has reached a near completion stage, it is time to test. You have to test the VUI you designed to check if it fulfills every benchmark on your checklist. There are two ways that you can use to test your prototype:
You can create groups of your targeted audience and then execute testing sessions to perceive how users are associating with your product, or, you can use this time for monitoring task completion rate and customer satisfaction score (CSAT).
Like other simulators used in mobile app development, Google and Amazon also provide tools for testing the designed product.

(iv). Refine

After your app has launched in the market, it is time for observation. It’s time to indulge in UX analytics. This stage looks at analyzing how the users are using your product.
Look at the -

  • Interaction per user or messages per interaction.
  • Languages used.
  • Intents and utterances.
  • User engagement metrics.
  • Behavior flows.

4. What is the Future of VUI?

We are bound to look at the views of every technology and voice as if they are no different. From what we have gathered from voice interfaces, we know that voice technology integration alone cannot fulfill the regular requirements of the users. The best way for it to become completely adopted is by shaking hands with a VUI like Google Assistant or Siri.
VUI and visual user interface collectively can even out each other’s deficiencies, providing users with an amazing voice assistant experience. Additionally, this will allow them to perform complex tasks with easy voice commands, which is what voice interfaces lack at this point in time.

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