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Kraxberger F, Näger C, Laudato M, Sundström E, Becker S, Mihaescu M, Kniesburges S, Schoder S. On the Alignment of Acoustic and Coupled Mechanic-Acoustic Eigenmodes in Phonation by Supraglottal Duct Variations. Bioengineering (Basel) 2023; 10:1369. [PMID: 38135960 PMCID: PMC10740796 DOI: 10.3390/bioengineering10121369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 11/15/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
Sound generation in human phonation and the underlying fluid-structure-acoustic interaction that describes the sound production mechanism are not fully understood. A previous experimental study, with a silicone made vocal fold model connected to a straight vocal tract pipe of fixed length, showed that vibroacoustic coupling can cause a deviation in the vocal fold vibration frequency. This occurred when the fundamental frequency of the vocal fold motion was close to the lowest acoustic resonance frequency of the pipe. What is not fully understood is how the vibroacoustic coupling is influenced by a varying vocal tract length. Presuming that this effect is a pure coupling of the acoustical effects, a numerical simulation model is established based on the computation of the mechanical-acoustic eigenvalue. With varying pipe lengths, the lowest acoustic resonance frequency was adjusted in the experiments and so in the simulation setup. In doing so, the evolution of the vocal folds' coupled eigenvalues and eigenmodes is investigated, which confirms the experimental findings. Finally, it was shown that for normal phonation conditions, the mechanical mode is the most efficient vibration pattern whenever the acoustic resonance of the pipe (lowest formant) is far away from the vocal folds' vibration frequency. Whenever the lowest formant is slightly lower than the mechanical vocal fold eigenfrequency, the coupled vocal fold motion pattern at the formant frequency dominates.
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Affiliation(s)
- Florian Kraxberger
- Institute of Fundamentals and Theory in Electrical Engineering (IGTE), Graz University of Technology, Inffeldgasse 18/I, 8010 Graz, Austria;
| | - Christoph Näger
- Institute of Fluid Mechanics (LSTM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 4, 91058 Erlangen, Germany; (C.N.); (S.B.)
| | - Marco Laudato
- Department of Engineering Mechanics, FLOW Research Center, KTH Royal Institute of Technology, Osquars Backe 18, 10044 Stockholm, Sweden; (M.L.); (E.S.); (M.M.)
| | - Elias Sundström
- Department of Engineering Mechanics, FLOW Research Center, KTH Royal Institute of Technology, Osquars Backe 18, 10044 Stockholm, Sweden; (M.L.); (E.S.); (M.M.)
| | - Stefan Becker
- Institute of Fluid Mechanics (LSTM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 4, 91058 Erlangen, Germany; (C.N.); (S.B.)
| | - Mihai Mihaescu
- Department of Engineering Mechanics, FLOW Research Center, KTH Royal Institute of Technology, Osquars Backe 18, 10044 Stockholm, Sweden; (M.L.); (E.S.); (M.M.)
| | - Stefan Kniesburges
- Division of Phoniatrics and Pediatric Audiology, Department of Otorhinolaryngology, Head & Neck Surgery, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 1, 91054 Erlangen, Germany;
| | - Stefan Schoder
- Institute of Fundamentals and Theory in Electrical Engineering (IGTE), Graz University of Technology, Inffeldgasse 18/I, 8010 Graz, Austria;
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