Evolution of adult male oral tract shapes for close and open vowels

Abstract

In this paper, we describe an experiment to evolve oral tract (mouth) shapes for a set of vowels for two adult males. Target vowels were recorded in an acoustically anechoic room along with the output from an electrolaryngograph, which monitors vocal fold vibrations electrically via two electrodes placed externally on the neck of the speaker at larynx level. Physical modelling digital waveguide synthesis using a two dimensional virtual oral tract was employed in the experiments. A population of 50 randomly shaped oral tracts were set up at the start of the evolution procedure, and the fitness of each was tested with respect to each of the target vowels. The resulting vowels are compared spectrally alongside the evolved oral tract shapes. The results for open vowels were close to the targets whereas those for close vowels were not. It is suggested that this is because of the associated narrow constriction to which special attention needs to be paid in the future.