Oscillazioni meccaniche in sistemi biologici

The purpose of this work is to study the mechanical vibrations field in two natural physical systems: vocal tract and heart. The mechanical vibrations associated with trachea and larynx when Italian vowels are emitted are investigated by using two laser Doppler vibrometers and compared with the acoustic ones. An upward propagation of the mechanical vibrations is observed for which it is possible to estimate a delay between the traces: the mechanical oscillations at the trachea start before the larynx and the acoustic oscillations. These tracheal oscillations are self-oscillations in time and are associated with the pitch production, indicating a further hydrodynamic instability at trachea. This leads to new insights in the mechanism controlling the pitch in the speech. We show that acoustical and mechanical vibration fields can be decomposed in two Landau modes which are limit cycles. The evidenced features of nonlinearity suggest a new phenomenological model of vocal tract. In this model the trachea plays an important role for in the generation of vowel sounds and contains information on the frequency of pitch. An alternative technique is suggested to monitor the proper functioning of the heart. The mechanical vibration associated with the heart are investigated by using two laser Doppler vibrometers. We show that the Hilbert transform of the recorded signal with the two vibrometers is the envelope of the electrocardiographic signal. This technique can provide an innovative and valuable diagnostic tool in the field of cardiology. [edited by Author]