PHYSICAL PROPERTIES OF SPEECH SOUNDS
•
We have concentrated for the most part on the articulatory
description of speech sounds
•
We describe consonants and vowels, the basic units of
speech sounds, along several parameters:
•
Articulatorily, consonants are described using three main
parameters:
•
State of the glottis (voiced/voiceless consonants)
•
Place or point of articulation (bilabial, velar, etc.)
•
Manner of articulation (stop/plosive, fricative, etc.)
Vowels are defined in terms of different set of criteria
•The parameters for vowel classification are:
•The height of the tongue ( high, mid, low vowels)
•The position of the tongue (front, central, back vowels)
•The rounding of the lips (rounded/unrounded vowels)
•The tongue root position (tense/lax or ±ATR vowels)
•Using the IPA we can represent vowels in a chart such as that
below
•[i] high front tense unrounded
vowel
•[u] high back rounded tense
vowel
ACOUSTIC PROPERTIES OF SPEECH SOUNDS
Besides those articulatory parameters, we can hear and study
sounds based on their physically quantifiable features
Speech as we have discovered is a continuous flow of varying
air pressure
Variations in air pressure in the form of sound waves move
through the air somewhat like ripples and on reaching the ear
cause the eardrum to vibrate
WAVE FORM DISPLAY
•Diagram of a waveform for [a], as in ‘caught’
Ladefoged (2001: 162)
READING ACOUSTIC DISPLAY
A display of a wave may not give a clue as to the exact nature
of the sound.
However,
•the manner of articulation is often clear
•If what is said is known, one can make some clear
judgments about manner transitions from one point to
the other in wave display
READING ACOUSTIC DISPLAY
READ THE ACOUSTIC DISPLAY
PROPERTIES OF SOUND WAVES
•Sound waves originate from the movement of
sound source or ‘piston’ , for example:
•Tuning fork (Jensen – p.18)
•The vibration of a tuning fork will produce a
sine wave – a regular or periodic wave
•Other vibrating bodies such as vocal cords:
•Vocal cords produce both periodic and
irregular wave forms – aperiodic wave
ELEMENTS OF SIMPLE SOUND WAVES
•THERE ARE TWO MAJOR FEATURES OF A SIMPLE
SOUND WAVE
1. FREQUENCY (MEASURED IN HERTZ (Hz))
•
This denotes the number of cycles of a sound wave
per second (2Hz = 2 cycles per sec, etc.).
1. AMPLITUDE (MEASURED IN DECIBELS (dB))
•
The maximum displacement of sound wave.
Amplitude in auditory terms is called LOUDNESS
ELEMENTS OF COMPLEX SOUND WAVES
•SOME SOUND WAVES ARE COMPLEX
A complex sound wave is made of several
simple sound waves, for example, speech
sounds.
THERE ARE TWO TYPES OF
COMPLEX WAVES
a. Periodic complex sound waves (vowels)
b. Aperiodic complex sound waves (most
consonants).
Additional feature of speech acoustics
In speech production the vibrating vocal cords acts
as the sound source
The frequency associated with the vibrating vocal
cords is called FUNDAMENTAL FREQUENCY
(F0) = PITCH (AUDITORILY)
THE RANGE OF HUMAN VOCAL CORD
VIBRATION IS BETWEEN 50HZ – 500HZ
RESONANCE
THE QUALITY OF CERTAIN SPEECH SOUND
DEPENDS ON ADDITIONAL ACOUSTIC FEATURES:
There is resonance from three major chambers:
•Pharyngeal cavity
Oral cavity
Nasal cavity
The frequencies associated with these cavities are called:
a.
pharynx resonance = F1
b.
oral resonance
= F2
c.
nasal
= F3
These are most useful for distinguishing different vowel
types in languages (Ladefoged 2001: 172 for AmE)
Phonological behavior of [+grave] sounds:
PIE *gwows “cow” > Anglo-Saxon cu; Gk bous
*gwiwos “living” > AS cwic; Gk. bios
Modern English: post-vocalic /l/ (a [+flat] allophone of /l/) has
disappeared or is disappearing in [+grave] environments:
walk, yolk, palm,
film, milk
help [hEp]
not in [-grave] environments: felt, silt,
See also: Ohala & Lorentz 1977 “The story of [w]” BLS 3.
[+flat] sounds are labialized, retroflexed, uvularized,
pharyngealized (vis-à-vis other sounds with otherwise
identical feature composition, e.g., /i/ = [-flat]; [y] = [+flat])
Prediction: no language will make us of [+flat] in more than
one of the above articulatory ways, e.g., no uvualrs plus
retroflexes; if retroflexes, then no uvulars; if distinctive
rounding, then no retroflexes, etc. This claim is not absolutely
true but it is valid statistically. There is no basis for this claim
with a purely articulatory descriptive system.
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there are two types of complex waves