Presentation on theme: "PHYSICAL PROPERTIES OF SPEECH SOUNDS"— Presentation transcript:
1 PHYSICAL PROPERTIES OF SPEECH SOUNDS We have concentrated for the most part on the articulatory description of speech soundsWe 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.)
2 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
3 ACOUSTIC PROPERTIES OF SPEECH SOUNDS Besides those articulatory parameters, we can hear and study sounds based on their physically quantifiable featuresSpeech as we have discovered is a continuous flow of varying air pressureVariations 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
4 Diagram of a waveform for [a], as in ‘caught’ WAVE FORM DISPLAYDiagram of a waveform for [a], as in ‘caught’Ladefoged (2001: 162)
5 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 clearIf what is said is known, one can make some clear judgments about manner transitions from one point to the other in wave display
8 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 waveOther vibrating bodies such as vocal cords:Vocal cords produce both periodic and irregular wave forms – aperiodic wave
9 ELEMENTS OF SIMPLE SOUND WAVES THERE ARE TWO MAJOR FEATURES OF A SIMPLE SOUND WAVEFREQUENCY (MEASURED IN HERTZ (Hz))This denotes the number of cycles of a sound wave per second (2Hz = 2 cycles per sec, etc.).AMPLITUDE (MEASURED IN DECIBELS (dB))The maximum displacement of sound wave. Amplitude in auditory terms is called LOUDNESS
10 ELEMENTS OF COMPLEX SOUND WAVES SOME SOUND WAVES ARE COMPLEXA complex sound wave is made of several simple sound waves, for example, speech sounds.THERE ARE TWO TYPES OF COMPLEX WAVESPeriodic complex sound waves (vowels)Aperiodic complex sound waves (most consonants).
11 Additional feature of speech acoustics In speech production the vibrating vocal cords acts as the sound sourceThe 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
12 RESONANCETHE QUALITY OF CERTAIN SPEECH SOUND DEPENDS ON ADDITIONAL ACOUSTIC FEATURES:There is resonance from three major chambers:Pharyngeal cavityOral cavityNasal cavityThe frequencies associated with these cavities are called:a. pharynx resonance = F1b. oral resonance = F2c. nasal = F3These are most useful for distinguishing different vowel types in languages (Ladefoged 2001: 172 for AmE)
13 Phonological behavior of [+grave] sounds: PIE *gwows “cow” > Anglo-Saxon cu; Gk bous*gwiwos “living” > AS cwic; Gk. biosModern English: post-vocalic /l/ (a [+flat] allophone of /l/) has disappeared or is disappearing in [+grave] environments:walk, yolk, palm,film, milkhelp [hEp]not in [-grave] environments: felt, silt,See also: Ohala & Lorentz 1977 “The story of [w]” BLS 3.
14 [+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.