Formant Studio analyses the sound of vowels spoken into the microphone. It works in real time. The program detects two dominant frequencies (called formants) in the sound spectrum and indicates them in the form of a cross on a plane with coordinate system. The horizontal position denotes one frequency and the vertical - the other. Each vowel has different formants, which correspond to some place on the plane. Such places have been designated with ellipses visible in the picture below. More details can be found in the help for the program.