Recent measurements with a synthetic two-layer model of the vocal folds and extension of Titze's surface wave model to a body-cover model.

The experiments of Mendelsohn and Zhang in 2011 (J. Acoust. Soc. Am. 130, 2961-2968) with six synthetic, two-layer models of the vocal folds were undertaken to better understand the role that the body layer plays in determining the properties of phonation. This rich data set provides an opportunity to extend Titze's surface wave model to a body-cover model. Much of Mendelsohn and Zhang's data can be interpreted with this model by assuming that the ratio of the spring constants of the two oscillators is that of the ratio of the Young's moduli for the two layers, and that the ratio of the masses of the oscillators is proportional to the ratio of the depths of the two layers.