Effects Of The Changes Of The Angle Of Epiglottis On Phonation And Resonance With Excised Canine Larynges

Objective:To explore the effects of the angle of epiglottis on phonation and resonance in excised canine larynges.Methods:The anatomic angle of epiglottis(Aepi)was measured for 14 excised canine larynges as a control.Then,the Aepi were manually adjusted to 60° and 90° in each larynx.Aerodynamic and acoustic parameters including mean flow rate(MFR),sound pressure level(SPL),jitter,shimmer,fundamental frequency(F0),phonation threshold pressure(PTP),phonation threshold flow(PTF),phonation threshold power(PTW),and formants(F1’-F4’)were measured with a subglottal pressure of 1.5 kPa.Simple linear regression analysis between acoustic and aerodynamic parameters and the Aepi of the control was performed and ANOVA comparing the acoustic and aerodynamic parameters of the three treatments was carried out.Results:(1)The larynges with larger anatomic Aepi had significantly lower jitter(p=0.005,r=-0.701),shimmer(p=0.018,r=-0.621),formant 1(p=0.013,r=-0.646),and formant 2(p=0.023,r=-0.602);(2)PTT and PTF was significantly different for the three treatments(PTP:P=0.019;PTF:P=0.002);(3)MFR and SPL were significantly different between the 60° and 90° treatments of 14 larynxes(MFR:P=0.022;SPL:P=0.023).Conclusion:The angle of epiglottis was defined for the first time in this study,which made the describe of position more precise,and we can understand the physiological function of the supraglottic structures better.We can conclude that:(1)The angle of epiglottis plays an important role in phonation and resonance of excised canine larynges;(2)MFR in the excised larynges with a bigger Aepi is larger,and is relatively hard to form turbulence during phonation,jitter and shimmer decline,while MFR and SPL increase;(3)When a Aepi of a larynx increases,the vocal tract tends to extend,so the frequency of F1’ and F2’ decrease,while PTP,PTF and PTW significantly increase.