Using time-temperature superposition to estimate the elastic shear modulus and dynamic viscosity of human vocal fold tissues at frequencies of phonation

Abstract

The principle of time-temperature superposition [J. D. Ferry, Viscoelastic Properties of Polymers (Wiley, New York, 1980), pp. 264–320] has been widely used by rheologists to estimate the viscoelastic properties of polymeric materials at time or frequency scales not readily accessible experimentally. This principle is based on the observation that for many polymeric systems molecular configurational changes that occur in a given time scale at a low temperature correspond to those that occur in a shorter time scale at a higher temperature. Thus the viscoelastic properties of these systems empirically measured at various temperatures at a certain frequency are indicative of measurements at different frequencies at a single reference temperature. Using a rotational rheometer, the elastic shear modulus and dynamic viscosity of human vocal fold mucosal tissues were measured at relatively low temperatures (5–25<th>°C) at 0.01–15 Hz. Data were empirically shifted based on this principle to yield a composite ‘‘master curve’’ which gives a prediction of the shear properties at higher frequencies at 37<th>°C. Results showed that the time-temperature superposition principle may be used to estimate the viscoelastic shear properties of vocal fold tissues at frequencies of vocal fold vibration, on the order of 100 Hz. [Work supported by NIH Grant No. P60 DC00976.]