Connecting the vowel formants to anatomical coefficients.

<p>We use the mapping described by Story et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080373#pone.0080373-Story2" target="_blank">[6]</a> to find the coefficients (<i>q</i>₁, <i>q</i>₂) corresponding to the first average formants <i>F</i>₁ and <i>F</i>₂ (kHz) of the Spanish vowels pronounced by our participants. This allowed the construction of a simple affine map connecting each Spanish vowel from the discrete motor space to their corresponding vocal tract configuration.</p

From transducer signals to binary vowel space.

<p>Upper right panel: sketch of Hall Effect transducers and magnets in the oral cavity. Transducers are marked with squares and magnets with circles. <i>Lips</i> (red): the transducer was attached to the center of the lower lip and the magnet was glued to the dental plastic replica, in between the central incisors. <i>Jaw</i> (green): magnet and transducer were glued to the dental replicas, in the space between the canine and the first premolar of the upper and lower teeth respectively. <i>Tongue</i> (blue): a cylindrical magnet was attached at a distance of 1.5 cm from the tip of the tongue. The corresponding Hall Effect transducer was glued to the dental plastic replica, at the hard palate, 1 cm right over the superior teeth (sagittal plane). Transducer wire was glued to the plastic replica and routed away to allow free mouth movements. Left, downwards: a spectrogram of the set of 5 vowels as pronounced by one of the subjects during a recording session (and frequency values for the first 2 formants) and the corresponding transducer signals for the lips, jaw and tongue. A binary code for each vowel can be defined by labeling the signal of each articulator as active (1) or inactive (0) as it reaches or not a predefined threshold (areas in color correspond to active motor coordinates). Lower right panel: resulting vowel-cube in the binary space. The edges of the cube represent an abstract space of size 8, were we explicitly locate the 5 vowels used in this work.</p