Transillumination of the Larynx in Running Speech

Abstract

A fundamental distinction between speech sounds depends on whether the excitation is a noise source or a quasiperiodic one. The noisy or voiceless sounds are presumably produced with an opened and quiescent larynx, while for voiced sounds the larynx is closed down and in rapid oscillation. Direct evidence of this has come from motion pictures recorded through the open mouth, a method obviously limited to particular sounds. Running speech requires different methods, and is being studied by a transillumination technique. A fiber-optics bundle introduced into the laryngeal vestibule through the nose is used to illuminate the glottis, while a photocell placed below the thyroid cartilage registers the variable light transmitted through the glottis and the tissues of the neck. The “glottograms” so obtained are compared with acoustic waveforms simultaneously recorded with air and throat microphones to determine how the voiced-voiceless distinction correlates with closed versus open states of the larynx.