H. J. L. Struycken was a Dutch otolaryngologist, phonetician, and acoustician. After studying medicine in Groningen, in 1893 he started working at the Voorburg psychiatric hospital near Vught, where he attempted to distinguish psychiatric conditions from neurological speech disorders. His interest in phonetics and acoustics took Struycken to France and Germany, to visit clinics and approach instrument makers who could produce tuning forks for him to use in his clinical research. In 1909, Struycken developed a methodology to visually record vocal sounds, using a small mirror to capture vocal curves. In otological circles, Struycken was known for his monochord, which generated longitudinal vibrations to determine the upper threshold of hearing. He was elected to the Royal Netherlands Academy of Arts and Sciences and to the board of the Dutch Sound Foundation.