VOIS3D (Vowel Overlap Indication Software - 3D)

__Contents:__

- What is VOIS3D?
- Running the Standalone Application
- Project Summary
- References and citation information

version information: (.exe) PC only [MAC users can run VOIS3D in a virtual Windows operating system environment, such as VMWare or Parallels]

VOIS3D is a software tool for acoustic phonetic, sociolinguistic, and experimental phonological research. VOIS3D integrates previous and new methods for vowel formant frequency normalization and duration normalization, with a new method for graphical vowel representation that allows numerical. This is possible because VOIS may take as its input either previously normalized vowel data, or raw data which may then be normalized as part of the graphing process.

__Big idea__: Normalized scatter for two vowel distributions is modeled as two best-fit ellipses oriented at angles with respect to F1, F2 axes. The output of the metric is an *overlap fraction*. The overlap fraction represents the area of the region of overlap (the region shared by both best-fit ellipses).

__Procedure__:

- Each observed vowel is plotted in a coordinate system where (x,y) = (normF1, normF2)
- Center each vowel class' datapoints around its own origin. (0,0) is the center of each system's vowel space. Determine the geometric formula for each ellipse and define a principal axis for each.
- Rotate each ellipse along its principal axis; determine the range of coordinates it occupies within its own 2D space.
- Using area information, determine extent of overlap between areas of Vowel 1 & Vowel 2. The output of this procedure is referred to as the "overlap fraction", a real-number value between 0-100%. (Wassink 1999,2006)

__Visualization functions in VOIS3D__:

- Scatterplot view (user's raw data).
- Two-dimensional overlap for raw or parametric data (parametric data shown).
- Ellipse view (2-dimensional view of parametric data). Raw scatter may be plotted with parametric ellipses (2-D) and ellipsoids (3-D) (shown in program screenshot, below).
- Three-dimensional overlap view for raw or parametric data (parametric data shown). Rotation of the cube is possible with the full version of VOIS3D running under MATLAB.