Acoustic properties of the nasal tract.

Sweep frequency measurements of the transfer function of nasals and nasalized vowels have been found to show a more complex pole-zero pattern than can be predicted with a traditional model of the nasal tract which consists of two parallel tubes coupled to the oral cavities. In this paper, we put forward the hypothesis that the more complex transfer function can be explained with reference to the shunting effect of the sinus maxillares and the sinus frontales. The two maxillar sinuses are situated in the bone symmetrically on the right and left side of the nasal tract. The two frontal sinuses are situated above the nasal tract in the bone of the forehead. These cavities are acoustically coupled to the nasal tract via short channels in the bone. Direct sweep tone data on the transfer function of the nasal tract support this hypothesis.