2.4.13. VoiceOver

For visually impaired people, voice over is one of the most useful functions. VoiceOver is a gesture-based screen reader. The user can utilize a mobile device even if they cannot see the screen. VoiceOver provides auditory explanations of what is on the screen.

On an iPhone, for example, when the user touches the screen or drags his finger over it, VoiceOver reads out the name of whatever the user touches, including icons and text. To interact with an item, such as a button or link, or to go to another item, the user can use VoiceOver gestures. VoiceOver creates a sound when the user moves to a new screen and then picks and speaks the name of the first item on the screen (typically in the top-left corner). VoiceOver tells the user when the display changes to the landscape or portrait orientation, the screen dims or locks, and what is active on the lock screen when the user turns on their iPhone [125].

The VoiceOver on iOS communicates with the user through a variety of "gestures", or motions made with one or more fingers on the screen. Many gestures are location sensitive. Sliding one's finger over the screen, for example, reveals the screen's visual contents as the finger passes over them. This allows visually impaired users to explore an application's actual on-screen layout. A person can activate a selected element by double-tapping, similar to double-clicking a mouse, in the same way a sighted user would. VoiceOver can also switch off the display while keeping the touch screen responsive, conserving battery life. This function is called the "Screen Curtain" by Apple [126].

### 2.4.14. Virtual Assistant Apps (Voice Commands)

Virtual assistants can help the visually impaired through their ability to control their mobile with voice commands. Here, we investigate the three most popular and recent virtual assistants: Siri, Google Assistant, and Bixby. One of the main concerns that we explore is privacy.
