The Power of Voice Interface Technology for Startups

Voice search is quickly becoming the next big thing. People, especially those of Generation Z, prefer to talk to their gadgets rather than touch them or punch buttons. This is not just something we made up; the popularity of voice search is supported by cold hard figures.

One of the most widely known predictions was made by ComScore as early as 2016. They said that by 2020, 50% of all search queries will be done with voice. Gartner is backing up this statement with its forecast that by 2021, the brands that embrace voice user interface and redesign their websites accordingly, will enjoy a 30% growth in commerce revenue. 

Finally, we have one more batch of statistics that may be interesting for e-commerce brands: by 2022, the amount of voice commerce sales is going to grow to as much as $5 billion in the UK and a whopping $40 billion in the US.


Image source: Wordstream

Now that we have convinced you that voice interfaces are worth investing in, let's see how they work and what VUI design best practices are trending in 2019.

Voice user interface 101

Let's begin with the definition. Voice user interface is the interface that allows users to control the device by voice commands. Rather than using their keyboards, mouse buttons or touchscreens, they use their voice to perform various actions. Voice user interfaces, or VUIs for short, are based on speech recognition technology, which translates spoken words into a machine-readable format.

Today, VUIs are implemented in most of the major platforms. If you are into Apple, you have Siri; if you prefer Google and Android, you have Google Assistant; while for you Microsoft adepts there is Cortana. Amazon has a voice interface of its own – Alexa - that is capable of performing multiple functions.

There are hundreds of options available to a voice interface user. In fact, a VUI can effectively do the same things that are done in a browser – find information, listen to music, manage calendars and appointments, place orders, make purchases, or play games. All that, and with hands free all the time!

Another great use case of VUI is its integration with smart home and other IoT-based systems. Being able to manage your house networks and appliances with your voice is a great convenience. Imagine telling your smart home to switch on the lights when you are coming through the door with your hands full or turning your thermostat up while still under the warm cover in bed! 

A mobile app with a VUI will offer a perfect solution for drivers who want to keep focused on their driving while searching for the information. If, for example, you are looking for a parking place and want to compare the prices at several garages, voice search will do the trick.

VUI advantages

The ability to communicate by voice is one of the unique features of humans, and its implementation in devices brings a whole range of clear advantages.

  • Speed of entry. Speaking always takes less time than typing, even for expert typists. For those who do not type as fast as professional typists, the speed of voice entry will be even more effective.
  • Intuitive control. In most cases, we need some time to understand how an interface works. With voice interfaces, that understanding comes naturally, as we all know how to speak. The ability to control the device with voice reduces the number of necessary instructions to the minimum.
  • Free hands. We have already mentioned the advantages of VUIs for drivers, but voice interfaces also allow you to use your devices when your hands are wet, greasy, or full of something. Another benefit is the convenience of device use for people who have poor control of their hand movements for whatever reason.
  • Screen size independence. Voice interfaces allow interaction with devices with small screens, such as smart watches.

However, for the sake of fairness, we need to mention a couple of cases where voice interfaces will not be the preferred option.

  • Lack of privacy. When you talk to your smartphone, everyone around you is going to hear. Therefore, it will not be a good idea to make financial arrangements or have a medical consultation via voice when you are in a public place.
  • Possible confusion in co-workings or office spaces. When multiple voice-operated devices are used in the same space, that might create confusion and also incorrect functioning, as devices may receive the wrong commands. Besides, imagine the noise level!

VUI use cases

While voice user interfaces can simply perform web browser functions, they may also become a valuable addition to mobile apps in various industry sectors. In fact, any business can benefit from implementing a voice interface. For example, let's check the list of Alexa skills and functions that this voice assistant can perform.

The list includes a couple of dozen categories with multiple apps in each. There is Business & Finance with online banking, credit card management, payment services, wallets, budget planners, and a lot more. In Travel & Transportation we will find route planners, visa reference resources, local guides, translators, and subway maps.

Other possible use cases include:

  • News feed
  • Fitness and wellness
  • eCommerce
  • Social applications
  • Music, movies and television
  • Connected homes and cars


As you can see, voice interfaces can be integrated with virtually any application. VUI becomes yet another channel of interaction between the user and the app functionality that is sometimes more convenient and user-friendly than the more traditional ones such as keyboards or touchscreens. The important thing is to design your voice user interface properly, so that it is easily usable and effective.

Designing a VUI

A common practice of designing and building VUIs is using the functionality of the major voice assistants, such as Alexa, Google Assistant, or Siri. All these voice assistants can be embedded in other devices or work as standalone components.

In order to enable the integration of their platforms into third-party apps, the major providers released their development kits allowing programming of custom voice-operated functions. Siri Kit, Google Assistant SDK, and Alexa Skills Kit are examples. By using the kits, you can make voice assistants perform commands related to your application.

However, before starting your voice user interface design, we recommend that you carry out user research to find out how the VUI will be used in your app.

User research

The user research is intended to show what users expect to achieve by operating their application via the VUI. The research usually consists of several steps:

Designing the customer journey map

Whether you are building a new voice-enabled app or integrating a VUI in an existing application, you will need a customer journey map showing the path that the user moves along to achieve the goal of your app. 

While mapping the customer journey, the VUI designer plans the points where voice interaction can be implemented. For example, in a weather forecast app it would be natural to enable the voice command “Show me the weather forecast for tonight”.

Analyzing user requirements

Before planning the VUI design, you should identify the requirements that users might have for your voice interface. A good method is to conduct user interviews, and to record your findings in the form of user stories. For example, if you are building a smart home app, you may have the following user story: “As a user, I want to give a voice command so that the kitchen lights are turned on”. By the way, the same users you asked to participate in the interviews may also help you later at the user testing stage, when you ask them to evaluate whether your design corresponds to their requirements and expectations.

Monitoring the competitors

See how your competitors use voice interfaces. By analyzing the applications of your competitors, and user reviews especially, you can see how they built their VUI, how the users rate their voice search UX, and whether their approach was successful or not. 

This knowledge may help you design your voice interface better and avoid the mistakes that the competitors made.

Voice command creation

After you have gathered the user stories, it is time to turn them into actual voice commands. Each voice command has three main components:

  • Intent – the goal that should be achieved with the command. For example, when the user says “Set the alarm for 6 am”, the intent is to have the alarm sound at 6 in the morning.
  • Utterance – the way the command is phrased. Different users may express the same intent with different phrases, and it is the job of the VUI designer to anticipate as many different utterances as possible. Such phrases as “Find flight tickets to Venice for Monday”, “Check if there are seats available to Venice for Monday”, and “I would like to book tickets to Venice for Monday” express the same intent but are different utterances. 

If you include multiple utterance options for the same intent, the chances that your voice assistant performs the task correctly will be much higher.

  • Mandatory or optional variables – additional information that is included in the utterance. If your command sounds like “Play me a movie”, it contains no variables but can still be executed; the application will offer any random movie. If, however, you say “Play me a sci-fi movie”, you are including an optional variable describing what kind of movie you prefer.

If you phrase a command like “Book me a hotel room”, it cannot be performed right away, because it is missing the mandatory variable – the place. 

Based on your user stories, create as many utterances as you can think of, so that the AI behind your app understands the user and performs correctly.

Dialog prototyping

Having taken into account all the above, it must be said that designing the commands is not enough to create a fully-functioning VUI. You need to prepare dialog prototypes creating the “scripts” by which the app is going to communicate with the user. 

The dialog prototypes should include all possible clarifications and alternative scenarios, allowing you to satisfy the user's intent. In our example above, when the user says, “Book me a hotel room”, the app should answer “Where would you like to go?” to find out the destination. 

To make dialog prototyping easier, you can use special VUI prototyping tools, such as Sayspring or Botsociety. Using such tools, you can build effective voice conversations creating great user experiences and allowing you to reach the goal expressed in the intent.


Image credit: TechCrunch

VUI design tips

Voice User Interface is a great technology, and by implementing it, you are already taking a huge step towards increasing your user engagement and retention. However, there are a couple of finer details that might make your app truly one of a kind.

  • Give your VUI a personality. Voice interfaces are intended to imitate human conversation, so make it as human-like as possible. Most popular voice assistants come with a sense of humor: one of the most famous of Alexa's lines is “Alexa, do you know Siri?” – “Only by reputation”. We do not mean that you should include lots of jokes in your app scripts, but make it friendly and emphatic. 
  • Include command confirmations in the VUI dialogs. To make sure that the app has understood the user correctly and is taking the required actions, make it repeat what it is doing. For example, when the user requests the app to book a flight, make it say something like “OK, now booking two economy class tickets from London to Warsaw for March 12 at 09:40”. 
  • Plan for errors. Always design the dialog so that whenever the app cannot recognize what the user is saying, it should say so. If any additional information is required to fulfil the request, script the dialog accordingly.
  • Include authentication. Most of the popular voice assistants can recognize individual voices, but still it would be wise to include an additional authentication measure. This way, you will make sure that the voice assistant will “obey” the person who is authorized to give commands. This additional security is especially critical when you are building a voice-enabled banking app or smart home app or some other app involving sensitive data.

VUI examples

Quite a lot of brands have already implemented VUIs as a quick and easy way of communicating with users and providing their services. Let's look at some of the top voice user interface examples.

Uber skill for Amazon Alexa

Uber lets its users book rides with their voice talking through Amazon Alexa. The corresponding skill is available in the list of Alexa skills to be added to the user's account.


Image credit: Amazon

BBC action for Google Assistant

BBC enabled a voice interface for its app. Now users can get the latest news bulletins by simply asking the assistant to play the news summary.


Image credit: Google

Domino's Pizza skill for Microsoft Cortana

For Cortana users, ordering a pizza with Domino's is as easy as saying it aloud. Domino's Pizza included its skill in the list of Cortana skills to enable voice ordering of its products.


Image credit: Microsoft

Wrapping up

In 2019, the importance of a voice interface for a consumer-facing startup cannot be overestimated. Voice assistants are quickly becoming as common as smartphones, which gives brands using VUIs additional opportunities to reach and retain customers. 

We will be glad to help you build a friendly voice interface for your app and consult you on the best ways of using the technology for your brand's benefit. Contact us to discuss the project in detail, and we will make sure your brand's voice will be heard.

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