Physics 1251 The Science and Technology of Musical Sound

1
Physics 1251The Science and Technology of
Musical Sound

• Unit 3
• Session 31 MWF
• The Fundamentals of the Human Voice

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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• What is the frequency of a palm pipe at 20 C
  that is 500 mm long and has an internal diameter
  of 35 mm? What are the first three audible
  harmonics?

A palm pipe is a stopped cylinder. Therefore f
1 v/4L' L' 0.500 m 0.3 (0.035 m)
0.5105 f 1 343/4(0.511) 85.75/0.511 168 Hz. E
3 33 f3 3f1 3 (168) 504 Hz. B4 35
f5 5f1 5 (168) 840 Hz. G5 ? 19
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• 1' Lecture
• The vocal folds, located in the larynx, produce
  vibrations in the vocal tract.
• The vocal tract is a stopped air column
  approximately 17 cm long. It resonates at a
  fundamental frequency of about 500 Hz.
• The shape of the vocal tract provides an acoustic
  filter of the harmonics produced by the vocal
  folds.

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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Anatomy of the Human Voice
• 80/20The vocal tract is the instrument of
  the human voice.

Vocal Tract

• Lungssource of air

Pharynx

• Tracheawind pipe

• Larynxvoice box

Larynx
Trachea

• Pharynxmouth and nose

Lungs
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Anatomy of the Human Voice
• 80/20The sound of the human voice originates in
  the larynx.

Larynx
Larynx
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Anatomy of the Human Voice
• 80/20The larynx (or voice box) contains the vocal
  folds.

Vocal Folds
Larynx
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Anatomy of the Human Voice
• 80/20The vocal folds rapidly open and close,
  introducing pulsations of air into the vocal
  tract.

Vocal Folds
Lower Vocal Tract
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Anatomy of the Human Voice
• 80/20The vocal folds rapidly open and close,
  introducing pulsations of air into the vocal
  tract.

Vocal Folds
Lower Vocal Tract
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Video of
• Laryngoscopy

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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• The Vocal Folds--Function
• 80/20The vocal folds are controlled by muscle and
  actuated by air moving between them, closing due
  to the Bernoulli Effect, opening by tension.

When flow is interrupted folds open.
Vocal Folds
Air Flow
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• The Vocal Folds
• 80/20The pressure waveform produced by the action
  of the vocal folds is an asymmetrical sawtooth,
  rich in harmonics.
• 80/20The fundamental frequency of the voice is
  determined by the properties of the vocal folds,
  not the vocal tract.

Vocal Folds snap open
are pulled shut by air flow
are pulled shut by air flow
are pulled shut by air flow
are pulled shut by air flow
are pulled shut by air flow
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Resonances of Vocal Tract

v 343 0.6(37-20) 353 m/s
500 Hz
1500 Hz
L 17 cm
2500 Hz
f1 v/4L 353/(4 ? 0.17) 519 Hz f3 3f1 ,
f5 5f1
80/20The Vocal Tract is a lossy stopped pipe
17 cm long with a fundamental frequency of 500
Hz.
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Formants of Vocal Tract

Amplitude
Formant
L 17 cm
Frequency
f1 v/4L 353/(4 ? 0.17) 519 Hz f3 3f1 ,
f5 5f1
80/20The Vocal Tract filters the spectrum
generated by the vocal folds the frequency
filter is called the Formant.
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Speech
• 80/20The individual units of speech are called
  phonemes.
• The classes of (English) phonemes are
• Unvoiced Plosives? p, t, soft k (c, q, x)
• Voiced Plosives? b, d, g
• Fricatives? f, v, th
• Sibilants? s (c) , z, sh, zh, j
• Liquids? l, r
• Nasals? m, n, ng
• Semi-vowels? w, y
• Vowels? a, e, i, o, u

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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Spectrogram of Human Speech

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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• 80/20The shape of the Vocal Tract determines the
  frequency of the Formants.

ah
eh
oh
oo
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Physics 1251 Unit 3 Session 31 The
Fundamentals of the Human Voice

• Summary
• The vocal folds, located in the larynx, produce
  vibrations in the vocal tract.
• The vocal tract is a stopped air column
  approximately 17 cm long, that resonates at
  500, 1500 and 2500 Hz.
• The shape of the vocal tract provides an acoustic
  filter, called the formant, that modifies the
  amplitude of the harmonics produced by the vocal
  folds.