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VUI 101

The purpose of this article is to (1) identify the most common problem areas faced by a Voice User Interface (VUI) developer, and (2) for each problem area, offer some concrete tips and established VUI best practices that you can immediately implement to enhance the performance of your voice application.

Opening the Call
The first and most important piece of information callers want to know when your application picks up the call is that they have reached the correct destination. A simple greeting, such as "Thank you for calling the ACME hardware store" suffices. After assuring callers that they are at their intended destination, the system should next provide callers with a menu of options. Prompts that offer a menu of spoken command choices are called selection prompts.

In those opening prompts, callers should be presented with not only a menu of options, but also with the site commands which the caller can use at any point during the call. (See below for more on site commands.)

NOTE: In applications where a caller needs to be at full attention in order to proceed, use the "When you are ready, say 'go on' device. This is particularly useful in survey applications, for instance, where the caller needs to be ready before taking on the first question.

Closing the Call
Calls end in one of three ways: (1) caller hangs up, (2) caller requests to exit the application, or (3) the application has reached the end of the call. There is little that the application can do about case (1). However, if the end of call was requested by the caller, it is always good practice to respond with a confirmation request, especially if the caller is aborting a task (e.g., collecting information).

Whether the call termination was initiated by the caller or the system, try to avoid announcing anything new or important at the call-closing prompt. After the caller says, "Goodbye", their attention to what the system is saying is minimal. At most, repeat some piece of information before closing with "goodbye": e.g., "Remember, your coupon is valid only through June 30th, 2004".

Site Commands
Site commands are instructions that callers can issue to the system at any point in the call, regardless of the context of the interaction. Applications which include site commands are typically considered the most user-friendly because callers always know what to say if they get lost within the application. A good practice is to mention the two most useful site commands - for instance, "Help" and "Repeat" - and to offer more detailed instructions if needed: "If at any point you need me to repeat something, just say 'repeat'. If you need more details on how to use the system, say 'instructions'."

Barge-In
Barge-in - the ability to interrupt a system prompt with voice or DTMF input -- is useful for experienced callers and should be turned on in most situations. There are three instances when barge-in should be turned off:

1. At the initial greeting prompt, since callers may still be listening to background information at the beginning of the application.
   
2. When the information being presented is crucial and you want the caller to listen to the whole prompt before responding (e.g., confirming that the caller wishes to transfer some amount of money).
   
3. When you want the caller to listen to an error prompt so that they fully understand the error and how they can correct it. For instance, if a caller thinks the system is expecting a date when in fact it is expecting a zip code, switching barge-in off so that the caller can hear, "Sorry, I didn't get that. Please give me your zip code.", would help the caller recover. If barge-in is on, the caller is liable to interrupt the prompt after, "Sorry, I didn't get that" and again mistakenly give the application a date.
   

Future newsletters will focus on a specific VUI-related topic and dig a little more deeply into the issues and solution techniques related to that topic. Readers are highly encouraged to share their thoughts on VUI issues by participating in the VUI Best Practices Forum within the Customer Knowledge Base or by sending me an email directly at bouzid@angel.com. User feedback will influence the content of future newsletters.
Ahmed Bouzid