The Laryngograph signal is obtained by placing two electrodes on the skin on either side of the thyroid cartilage of the larynx. A harmless high frequency current  (3 MHz) is applied between the two electrodes held at a constant voltage. When the vocal folds vibrate there is a change in electrical conductance between the electrodes which reflects  the change in contact area between the mucosa of the two vocal folds during a vibratory cycle. This signal is displayed on the computer screen as the Laryngograph waveform (Lx waveform).