Editing Wolfgang von Kempelen's Speaking Machine (1769) (section)

==== 1. Contributions to linguistic research： ====
While before Von Kempelen the larynx was considered central to speech production, his simple and successful demonstration drew the attention of 19th-century scientists to the vocal tract, the cavity between the glottis and the lips, as the main site of acoustic articulation.<ref name=":2" /> In his book, he classifies the vowels according to her width of the lip channel giving a ranking of A >E>I>0>U and the width of the so called tongue channel that can be interpreted as horizontal tongue position. Although Kempelen isn't very explicit here, the observation clearly resembles the perceptual analysis of the second formant in whispered vowels described a century before by Reyher (1679) and the vowel tunes of [[wikipedia:Hermann_von_Helmholtz|von Helmholtz]] (1862). <ref name=":3">Pompino-Marschall, Bernd. “Von Kempelen’s Contribution to the Theory of Acoustic Articulation,” n.d.</ref>This innovative vowel classification (classifying vowels based on characteristics like the width of the lip channel and tongue channel) represented a novel approach to the study of speech sound physical properties.