This chapter traces the historical and epistemological development of the notion of timbre, from early descriptive uses to its modern acoustic and physical theorization, with a particular focus on speech sounds. In contemporary phonetics, timbre is defined as a perceptual property linked to the spectral distribution of acoustic energy, especially the formant structure shaped by the vocal tract. This perspective is framed within the source–filter theory proposed by Gunnar Fant, which conceives timbre as the result of vocal-tract filtering rather than a global auditory impression. The chapter then examines the historical construction of the concept. Lexicographic sources show that before the nineteenth century, timbre primarily referred to instruments such as bells or tambourines, before acquiring figurative meanings related to voice and resonance. In parallel, musicology and acoustics gradually moved beyond purely numerical conceptions of sound intervals toward an empirical recognition of harmonics, notably in the works of Joseph Sauveur. A major conceptual shift occurs at the end of the eighteenth century with Gaspard Monge, who proposed that timbre depends on the order and number of partial vibrations. Although initially contested, this hypothesis gained physical support through Jean-Baptiste Biot and was further developed experimentally by Franciscus Cornelis Donders. These developments culminate in the work of Hermann von Helmholtz, who established timbre as a measurable acoustic phenomenon grounded in harmonic structure, later extending its conceptual legacy to electromagnetism through Henrich Rudolf Hertz and Edouard Branly.
Schweitzer et al. (Mon,) studied this question.