Microphonic Effect of the Larynx

Abstract

IN order to test a hypothesis¹ on the origin of the vibrations of the vocal folds—the vibrations were supposed to start coup pour coup at a contraction of the m. vocalis internus induced by an action potential along the corresponding fibres in the n. recurrens—we made some simultaneous recordings on the electromyogram of the m. thyreo-arytenoideus and the sound curve with a very suitable patient in Prof. H. A. E. van Dishoeck's Otorhinolaryngological Clinic, University of Leyden. This patient had a stoma just above the larynx and the internal laryngeal muscles presented themselves directly. One vocal fold was normal, the other one was slightly less movable. Phonation was practically normal; the patient only used the chest voice. Two very thin needle electrodes were put into the normal m. thyreoarytenoideus, about 1.5 mm. from the glottis and about 1.5 mm. deep, one at the anterior side, the other one near the arytenoid. We thus recorded the myogram of the whole muscle instead of the activity of a small part, as is done with thin concentric needle electrodes.