There is only one file type that uses the .VOCA extension:
PhotoVOCA Communication Board File
A VOCA file is a digital communication board created by PhotoVOCA, an iOS app used to create digital communication boards. It is compressed with .ZIP compression and contains data which includes audio and .PNG image assets with an .XML manifest. VOCA files are saved in the PhotoVOCA 3.0 format, which is an extension of the original VOCA format released in 2010 by PhotoVOCA.
A communication board is a board with pictures or symbols attached to help children with limited expressive language ability facilitate communication. The children can point at the images on the board to communicate. Digital communication boards are the same as communication boards except they are used on electronic devices such as computers and tablets. The VOCA file can be opened by Assistive Technology Communication applications, which are also known as Augmentative and Alternative Communication (AAC) or Speech Generation Devices (SGD).
The PhotoVOCA 3.0 format is similar to the old VOCA format released in 2010 with the original PhotoVOCA app. The difference between the two file formats is the addition of new elements/attributes to the XML.
Updated: May 20, 2017