Sonotubometry is usually performed with 8 kHz signals. The quality can be limited by noise pollution from the pharynx. The author present a new approach by applyling perfect sequences (PS).
Perfect sequences are periodically repeated noise signals. These are applied with a sample rate of 32 kHz into the nose. The increase of sound pressure during tube openings is recorded in the external ear canal. With a special software the calculation of the changes in the broad band frequency spectrum is possible. Valuable information about tube activity can be extracted from a spectrum up to 16 kHz. In twenty healthy probands the use of this new signal was surveyed. All were measured during swallowing, yawning and Valsalva manoeuvre with PS and 8 kHz.
Openings were detected with both methods in all patients but not in all maneouvres. With PS in 19% more manoeuvres an opening could be found (0.05>p). PS demonstrated that signals at 2 and also at 4 kHz contain valuable information about the tube opening. The quality of the measurements was with PS in 46% better, in 51% the same and in 3% worse as compared to 8 kHz signals.
Perfect sequences represent a promising approach for the recording of Eustachian tube activity. This method may improve the assessment of the dynamic tube function in future.