Formant Comparisons and Identifying the Speaker

After everything is broken down, all that is left for the system to do is the easy part – make a simple comparison between the input formants and the formant in the database. The first step is in determining which vowel is actually being spoken. This is simply an examination of the location of the first two formant peaks. If they both fall within the range of a specific vowel’s first two formants, they are representing that vowel. That range is stored within the database. These ranges are very well defined for each individual vowel and are adjusted to the members of the group. For example, the first formant of a vowel has a range that will include formants at frequencies just above the highest frequency first formant in the group and just below the lowest frequency first formant. If it does not fall in the range of the vowel, that vowel is not the correct one, and it continues to try the next vowel. It repeats this process until either it finds a vowel or goes through all vowel sounds in the database. If the formants do not fall within any particular formant range, the vowel sound will be ignored.

The second step is the actual comparison. The frequency response of the input vowel sound is multiplied in a dot product with each member’s previously stored frequency response for the vowel. This is the vowel that was determined in the first step. A resulting score matrix is produced from the dot product. The score matrix will output a value from 0 to 1, with 1 being a perfect match and a 0 being an entirely incorrect match.

This process is repeated for each vowel sound in the word. The score matrices are then added together, and the system identifies the speaker as the individual with the highest score. If, however, that individual does not pass a threshold value, then the system determines there is no match.