Behind the Complex Interplay of Phonation: Investigating Elasticity of Vocal Folds With Pipette Aspiration Technique During Ex Vivo Phonation Experiments

Flow-induced oscillations of vocal-fold replicas with tuned extensibility and material properties

“…Such unexpected strain-induced variations are at odds with in vivo observations on real human vocal folds during glissando, where increases with . Nor are they consistent with very recent experiments carried out on excised animal larynges, instrumented to monitor longitudinal elongation of the folds 53 , in which an increase in phonation frequency was also measured with pre-strain – albeit in a region of lower values up to 0.06 at most. However, our results are in agreement with measurements made by Shaw et al 26 on synthetic vocal-fold models with quasi-linear and isotropic mechanical properties, for which they showed that the frequency decreased slightly with fold elongation.…”

“…6 c). Based on previous sparse ex vivo 53 and in vitro evidences 25 as well as numerical predictions 39 , 43 , this increase of phonation frequency with material stiffness is expected – even though all absolute values of measured in the present work are very low compared to the ones encountered in standard male/female modal speech. pre-stretching the folds has a decreasing impact on for all replicas, as shown in Fig.…”

“…These non-physiological tendencies can be explained by several discrepancies that remain between the histo-mechanical characteristics of a biological larynx and our current in vitro idealization: firstly, the longitudinal tensile response of all the materials studied in this work is still quite far from that of native vocal-fold tissues, even for the optimized hydrogel, due to its isotropy. In particular, the non-linear strain-hardening of tangent moduli observed on excised human 34 , 59 , 114 or animal vocal folds 52 , 53 , which is linked to the progressive recruitment, deployment and reorientation of collagen fibres towards the load direction 34 , 35 , 49 , 115 , is not yet reproduced 26 , 48 ; then, the laryngeal envelope and induced boundary conditions are probably still too soft to mimic the stiffness of native cartilages; the “active” hardening of the vocalis during its contraction in vivo is also left out of the current replica. Finally, the sound quality produced by the four candidates is affected.…”

“…Thus, in recent years, while improving current manufacturing procedures 45 , 46 , the search for optimal materials 47 – 49 , multi-scale structures 49 and mechanical control 50 , 51 for increasingly “bio-/phono-mimetic” vocal-fold replicas is the subject of active investigation. However: Even though vocal-fold stretching is a major aspect of phonation biomechanical control 3 , 32 – 35 , 39 , 52 , 53 , the number of in vitro studies involving experimental models of vocal folds able to measure and control the laryngeal longitudinal pre-strain occurring before any phonatory event is very limited. To our knowledge, although several earlier models were able to tailor fold shape and/or internal tension in pre-phonatory posture 19 , 22 , 23 , 54 , only two published studies have presented articulated folds that allow different degrees of anterior–posterior fold lengthening to be set 26 , 50 .…”