p105 lecture #26 visuals
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P105 Lecture #26 visuals. 18 March 2013. Anatomy of the Human Vocal Apparatus. Illustration from E.J. Heller, “Why you hear what you hear”. Vocal Tract Anatomy – Another View. Illustration from J. Sundberg , “The Acoustics of the Singing Voice”. Vocal Tract Anatomy – Another View. - PowerPoint PPT PresentationTRANSCRIPT
P105 Lecture #26 visuals
18 March 2013
Anatomy of the Human Vocal Apparatus
Illustration from E.J. Heller, “Why you hear what you hear”
Vocal Tract Anatomy – Another View
Illustration from J. Sundberg, “The Acoustics of the Singing Voice”
Vocal Tract Anatomy – Another View
• Sound wave production starts with the larynx
Vocal Tract Anatomy – The Larynx
Illustrations from E.J. Heller, “Why you hear what you hear”
View from above:Frontal view:
Bernoulli Effect
• Discovered by Daniel Bernoulli in the mid 1700’s
• Essentially a consequence of conservation of energy
• Statement is that pressure and flow velocity are inversely related for incompressible (approx. constant density) fluid
• Mathematically: p1 + ½ r1 v12 = p2 + ½ r2 v2
2
(where p = pressure, r = density, v = velocity)
Function of the Vocal Folds
Illustration from A.H. Benade, “Fundamentals of musical acoustics”
Can think of the vocal folds as a mass/spring system. Operates via Bernoulli Effect: expulsion of air from lungs high flow through glottal opening
Low pressure closes vocal folds flow stops folds openRepeat.
Net Result: Periodic expulsion of “puffs” of air from lungs
From Rossing, Wheeler & Moore, The Science of Sound
Top: volume velocity vs time for sound production at 125 Hz (male voice); Bottom:Power spectrum falls at 12 dB per octave
Fourier Spectrum:
Sound Production Summary• Expulsion of air from lungs induces vibration of vocal folds (via the Bernoulli
effect).
• The vocal folds open and close with a frequency dictated by anatomy (geometry) plus applied tension (contraction of muscles connecting folds with cartilage).
• Give rise to periodic puff emission with fundamentals around 100 Hz (male), 200 Hz (female), 300 Hz (children). These are just the vocal fold vibration frequencies.
• Thus, the vocal fold vibration frequency sets the pitch
• To understand harmonic structure of speech must also take into account the filtering effect of the vocal tract next up.