Transcript Physics 1251 The Science and Technology of Musical Sound

Physics 1251
The Science and Technology
of Musical Sound
Unit 3
Session 31 MWF
The Fundamentals of the
Human Voice
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 ¢]
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.
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:
• Lungs—source of air
• Trachea—wind pipe
• Larynx—voice box
• Pharynx—mouth and
nose
Pharynx
Larynx
Lungs
Trachea
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
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
Closed
Open
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
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
Physics 1251
Unit 3 Session 31
The Fundamentals of the Human Voice
Video of
Laryngoscopy
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.
Phonation
When flow is
interrupted
folds open.
Air Flow
Vocal Folds
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
are pulled
open shut by air flow
Physics 1251
Unit 3 Session 31
The Fundamentals of the Human Voice
Resonances of Vocal Tract
L≈ 17 cm
v =343 + 0.6(37-20) =353 m/s
~500 Hz
~1500 Hz
~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.
Physics 1251
Unit 3 Session 31
The Fundamentals of the Human Voice
L≈ 17 cm
Amplitude
Formants of Vocal Tract
Formant
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.
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
Physics 1251
Unit 3 Session 31
The Fundamentals of the Human Voice
Spectrogram of Human Speech
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”
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.