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 F1F2F3F4

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 F 1 = c/4 l Where 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 F 1 For example,  F 1 = (c/4l )*1  F 2 = (c/4l )*3  F 3 = (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 … Area (cm 2 ) Length along tube (cm)

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

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 vowel F1: 500 Hz F2: 1500 Hz /i/ /u/ //// //// frequency Gain