The Tomatis electronic ear is a device that could modify the natural audio feedback between the emitted voice and the ears of a talking or singing individual. Our aim was to test if the device causes quantifiable vocal variations having the subjects repeat sustained vowel sounds (i.e. /a/, /i/, /u/) with different frequency filters applied by the device. The subjects are 19 native adult Italian speakers (8 females) testing 4 different filtering methodologies: unfiltered feedback (control), low pass filter at 4 kHz, high pass filter at 4 kHz and a high pass filter at 8 kHz. All subjects quantifiably modified their vocalization in response to the varying methodologies for at least one letter of each filtering method: 81.29% of the sessions of all subjects were significantly different in fundamental frequency from the control (p<0.05, Kruskal-Wallis test). Among subjects, the variation trend was significant only for the fundamental frequency of the letter /u/ of a particular subgroups categorized by mean fundamental frequency. This initial work shows that the vocal variations caused by the Tomatis device are quantifiable but subject specific, laying the groundwork to test new parameters to find common trends of configurations.
