Contribution of paranasal sinuses to the acoustic properties of the nasal tract.

BACKGROUND

The contribution of the nasal and paranasal cavities to the vocal tract resonator properties is unclear. Here we investigate these resonance phenomena of the sinonasal tract in isolation in a cadaver and compare the results with those gained in a simplified brass tube model.

METHODS

The resonance characteristics were measured as the response to sine sweep excitation from an earphone. In the brass model the earphone was placed at the closed end and in the cadaver in the epipharynx. The response was picked up by a microphone placed at the open end of the model and at the nostrils, respectively. A shunting cavity with varied volumes was connected to the model and the effects on the response curve were determined. In the cadaver, different conditions with blocked and unblocked middle meatus and sphenoidal ostium were tested. Additionally, infundibulotomy was performed allowing direct access to and selective occlusion of the maxillary ostium.

RESULTS

In both the brass model and the cadaver, a baseline condition with no cavities included produced response curves with clear resonance peaks separated by valleys. Marked dips occurred when shunting cavities were attached to the model. The frequencies of these dips decreased with increasing shunting volume. In the cadaver, a marked dip was observed after removing the unilateral occlusion of the middle meatus and the sphenoidal ostium. Another marked dip was detected at low frequency after removal of the occlusion of the maxillary ostium following infundibulotomy.

CONCLUSION

Combining measurements on a simplified nasal model with measurements in a cadaveric sinonasal tract seems a promising method for shedding light on the acoustic properties of the nasal resonator.