This map shows the data for Australians, as at 26/09/2007. What does this graph mean?
The two most important parameters in determining different vowel sounds are the first two formants, which are frequency bands with increased power. These are the two axes on the graph. The axes are traditionally plotted backwards, as here, so that they approximately correspond to the axes long used by phoneticians and linguists: F1 (vertical) approximately corresponds to the jaw height (which correlates negatively with the extent of the mouth opening). F2 (horizontal) approximately corresponds to the position (forward or back) of the constriction of the vocal tract where the tongue is close to the roof of the mouth. Other important parameters are the length of the vowel and other formants. More about the science of speech.
"Short" on a vowel means that more than 75% of our subjects' selections were short and analogously for "long". This graph shows the map of how this group of subjects (a small number, early in the life of the study) recognise vowels with particular values of F1, F2 and vowel length. This graph probably corresponds closely to the graph for their accents, or for the accent of English they are most used to hearing. When we obtain enough (serious) surveys, we shall have maps for different countries and different regions, so thank you very much for participating!