title: Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors.
abstract: OBJECTIVE
  The aim of the study was to measure the influence of the maxillary central incisors free from adaptation phenomena using spectral analysis.
  
  
  METHODS
  The maxillary dentures of 18 subjects were duplicated. The central incisors were fixed in a pivoting appliance so that their position could be changed from labial to palatal direction. A mechanical push/pull cable enabled the incisor section to be handled extraorally. Connected to the control was a sound generator producing a sinus wave whose frequency was related to the central incisor angulation. This acoustic signal was recorded on one channel of a digital tape recorder. After calibration of the unit, the denture duplicate was inserted into the subject's mouth, and the signal of the /s/ sounds subsequently produced by the subject was recorded on the second channel during alteration of the inclination angle simultaneously with the generator signal. Spectral analysis was performed using a Kay Speech-Lab 4300B.
  
  
  RESULTS
  Labial displacement in particular produced significant changes in spectral characteristics, with the lower boundary frequency of the /s/ sound being raised and the upper boundary frequency being reduced.
  
  
  CONCLUSIONS
  Maxillary incisor position influences /s/ sound production. Displacement of the maxillary incisors must be considered a cause of immediate changes in /s/ sound distortion. Therefore, denture teeth should be placed in the original tooth position as accurately as possible. Our results also indicate that neuromuscular reactions are more important for initial speech sound distortions than are aerodynamic changes in the anterior speech sound-producing areas.
authors.affiliation: Department of Prosthodontics, University of Muenster, Waldeyer Strasse 30, D-48149 Muenster, Germany. crunte@uni-muenster.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Runte
authors.forename: Djafar
authors.initials: D
authors.lastname: Tawana
authors.forename: Dieter
authors.initials: D
authors.lastname: Dirksen
authors.forename: Bettina
authors.initials: B
authors.lastname: Runte
authors.forename: Antoinette
authors.initials: A
authors.lastname: Lamprecht-Dinnesen
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Bollmann
authors.forename: Eberhard
authors.initials: E
authors.lastname: Seifert
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Danesh
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003779:Denture Design; D003827:Denture, Complete, Upper; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007180:Incisor / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010700:Phonetics; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013223:Statistics as Topic; D013499:Surface Properties