Frequency response of the Fourcin electroglottograph and measurement of temporal aspects of laryngeal movement during swallowing.

The purpose of this investigation was to study the frequency response of a modified Fourcin EGG at frequencies associated with the slow varying laryngeal movement of swallowing and to compare those findings with the response characteristics of the EGG at frequencies associated with phonation. Frequency-dependent differences were found. At very low frequencies the EGG output was found to be the derivative of the changes in neck impedance; at higher frequencies the EGG output directly represented the changes in neck impedance. Three of the four phases of the pharyngeal stage of the swallow are represented by the EGG signal.