Vowels

Vowels: Articulatory Description

(Ferrand, 2001)

Tongue Position

Vowels: Articulatory Description Degree of lip rounding

Rounded Unrounded

Degree of tension Tense Lax

Source-filter theory revisited

Vowels: Acoustic Description

Vocal tract as a tube Tubes have physical

characteristics Tubes are acoustic

resonators Acoustic resonators

have frequency response curves (FRC) (or transfer functions)

Physical characteristics dictate FRC

Frequency response curve (FRC) FRC peaks – resonant

or formant frequency Resonators have an

infinite number of formants

F1, F2, F3 … denotes formants from low to high frequency

F1 F2 F3 F4

Formant Patterns for the “Noncentral” (i.e., omitting

/ú/ and /ü/) Monophthongal Vowels of American English (based on Peterson & Barney averages)

Characteristics affecting filter properties

Overall length Whether it is closed at either or both ends Cross-sectional area along its length

Uniform tube closed at one end

First resonance or formant

F1 = c/4lWhere

c=speed of sound (35,000 cm/sec)

l = length of the tube

males ~ 17.5 cm

females ~ 14 cm

Higher resonant/formant frequencies are odd multiples of F1

For example, F1 = (c/4l )*1

F2 = (c/4l )*3

F3 = (c/4l )*5

The vocal tract Can be (roughly) uniform in shape Can also be take on non-uniform shapes Non-uniform tubes

Have a more complex area function Does not allow simple calculations of resonances

Area function of a tube

…

Are

a (c

m2)

Length along tube (cm)

Vocal Tract Area Function

Vocal Tract Area Function

FRC

Key point Vocal Tract has a variable shape, therefore

It is a variable resonator Can have a variety of area functions Can generate a variety of frequency response

curves

FRC

FRC

FRC

What distinguishes vowels in production and perception?

Resonant (formant) Frequency F1, F2 frequency are

particularly important F3 frequency plays a

smaller role

Landmark study: Peterson and Barney (1952)

Median values based on lab measures

Mid Central vowelF1: 500 HzF2: 1500 Hz

/i/

/u/

//

//

frequency

Gai

n