Acoustic phonetics: The study of the transmission and the physical properties of speech sounds

Transcription

1 LING 1001 Page 1 Chapter 2 File 2.0 What is phonetics? Articulatory phonetics: The study of the production of speech sounds Acoustic phonetics: The study of the transmission and the physical properties of speech sounds Auditory phonetics: The study of the perception of speech sounds File 2.1 Representing speech sounds Xray photography was once used to track the articulation of speech sounds, however, the amount of radiation involved was dangerous for the subjects More recent methods include the electromagnetic articulograph to track the locations of small receptors on the lips, tongue, and jaw Palatography: Observing contact between the tongue and the roof of the mouth (the hard palate) Articulatory phonetics also uses instruments to measure airflow and air pressure during speech Acoustic phonetics focuses on the sounds produced by articulations Sound spectograph: Captures speech sounds in a visual format Advanced study of auditory phonetics depends on MRI and CT scans Impressionistic phonetic transmission: Transcribing what you've heard, the way it sounded rather than the way the words used are spelled A good phonetic transcription system aims to unambiguously convey the important aspects of the pronunciation of a given set of sounds: First, each symbol shall represent only one sound (a phone) Second, if two sounds distinguish two words from each other, they should be represented by different symbols Third, if two sounds are very similar and only differ based on context, they are written with the same symbols (the change is predictable based on the context the sound is found in) Segment: The discrete units of the speech stream consonants and vowels Suprasegmentals: Ride on top of segments and apply to entire strings of consonants and vowels properties such as stress, tone, and intonaton Consonants are produced with a constriction somewhere in the vocal tract that impedes airflow much quieter than vowels and usually cannot function as the heart of a syllable Vowels are produced with (at most) only a slight narrowing and allow air to flow freely through the oral cavity louder than consonants, and function as the heart of a syllable, carrying suprasegmental information such as stress, loudness, and pitch Nucleus (of a syllable): The heart of a syllable, carrying suprasegmental information such as stress, loudness, and pitch Monophthongs: Simple vowels, composed of a single configuration of the vocal tract Diphthongs: Complex vowels, composed of a sequence of two different configurations but the sequence acts as the nucleus to a single syllable Running speech (continuous speech): Phrases and sentences, with the words all run together the pronunciations of words may be affected by the surround words File 2.2 Articulation: English consonants Articulatory description: The voicing, place of articulation, and manner of articulation of a consonant Articulation: The motion or positioning of some part of the vocal tract with respect to another vocal

2 LING 1001 Page 2 tract surface in the production of a speech sound Pulmonic egressive airstream mechanism: The airstream mechanism used to create sounds by exhaling Airstream mechanism: The configuration of the vocal tract used in a particular manner of the production of speech sounds Segmental features: The voicing, place, and manner of articulation of a speech sound Larynx: Sometimes called the voice box contains the vocal folds and the glottis Vocal tract: Above the larynx, composed of the oral and nasal cavities Subglottal system: Part of the respiratory system, located below the larynx Trachea: The windpipe Vocal folds: The muscles involved in speech production, move back and forth to allow air to pass through freely or create vibration as it passes through Glottis: The opening between the vocal folds Voiced sounds: Sounds produced by vibration of the vocal folds Voiceless sounds: Sounds produced without vibration of the vocal folds Spectrogram: A picture of the acoustic signal of a sound can indicate whether vocal fold vibrations are present in a sound Another option is to insert a thing fiberoptic line through the nostril of the subject and capture the vocal folds in action with a highspeed camera however, this procedure is invasive and requires the presence of welltrained medical personnel, despite its clear picture of the adjustments and movements of the vocal folds Places of articulation: Where in the vocal tract a consonant is made Bilabial: Bringing the two lips together Labiodental: The lower lip going towards the upper teeth Interdental: The tongue tip touching the upper teeth Alveolar: The tongue tip touching the alveolar ridge behind the front teeth Retroflex: The tongue tip at the back of the alveolar ridge Palatal: The tongue at the front of the hard palate Velar: The tongue towards the back, at the soft palate behind the hard palate Uvular: The tongue towards the back, near the uvula Pharyngeal: Made at the root of the tongue, at the back wall of the pharynx Glottal: Made with the vocal folds in the larynx Manners of articulation: How the airstream is modified by the vocal tract to produce the sound Stop: Made by obstructing the airstream completely in the oral cavity Glottal stop: Made by momentarily closing the vocal folds Fricative: Made by forming a nearly complete obstruction of the vocal tract, creating a turbulent noise called frication Affricate: Made by briefly stopping the airstream completely and then releasing the articulators slightly so that frication noise is produced a sequence of a stop followed by a fricative Nasal: Produced by lowering the velum and opening the nasal passage to the vocal tract can also be called nasal stops, because the vocal tract is completely obstructed Liquid: Involve a substantial constriction of the vocal tract, but not narrow enough to block the vocal tract or cause turbulence for example, in a lateral liquid, there's a side passage around the tongue Glide: Made with only a slight closure of the articulators, so that if the vocal tract were any more open, the result would be a vowel sound Flap: Similar to a stop, with a complete obstruction of the oral cavity, but much faster than a stop the articulators strike each other very quickly In palatography, a picture is made that shows where the tongue touches the roof of the mouth during a particular articulation. Static palatography: A form of palatography that involves painting the tongue black with a tasteless mixture of olive oil and charcoal powder. The speaker rinses in between articulation. Works only if the speaker produces a single isolated sound and the contact pattern is photographed immediately.

3 LING 1001 Page 3 Dynamic palatography: How one consonant's place of articulation affects another's also called EPG, for electropalatography. Allows computer recording of a sequence of contacts as the tongue makes contact with an artificial hard palate (custom made for each subject) with small embedded electrodes to record contact as soon as the tongue moves against them. Can track where, how much, and how long contact between the tongue and roof of the mouth lasted at any given time in an utterance. Coarticulation of segments: When the articulation of one sound is affected by the sounds around it, which can't be captured by standard transcriptions File 2.3 Articulation: English vowels Vowels are the most intense and audible speech sounds consonants that surround them often depend on the vowel for their audibility Vowels are almost always voiced, and have no point of articulation or manner of articulation Factors affecting vowel pronunciation: Tongue height: Low vowels are made with the front of the mouth open so the tongue body can be lowered away from the roof of the mouth, while high vowels are made with the tongue body close to the roof of the mouth Tongue advancement: Frontvowels are made with the body of the tongue pushed forward, while back vowels are made with the body of the tongue in the back of the mouth Lip rounding: Vowels can be made either with the lips rounded or unrounded English uses only a few rounded vowels Tenseness: Tense vowels have more extreme positions of the tongue and lips than vowels that are lax they have greater changes from the midcentral position in the mouth high vowels are higher, front vowels are further forward Vowel space: The space used in the mouth to pronounce vowels tense vowels reach the periphery of this Diphthongs: Complex vowels composed of two vowel sounds, transitioning from one vowel to the other in the same syllable Previous methods for researching vowel articulation included x ray films of people talking, but this method is no longer used as it was harmful for the speakers More recent technologies include MRI or Electromagnetic Articulography (EMA) MRI uses invisble rays to create a visual image of the vocal tract, while EMA involves placing small sensors on the subject's articulators that transmit information to a computer

4 LING 1001 Page 4 File 2.4 Beyond English: Speech sounds of the world's languages German and French both have front rounded vowels, which are not present in English All languages have oral vowels, and many only have oral vowels however, there are also nasalized vowels made with the nasal passage opened, much like a nasal stop compared to an oral stop these are written with a tilde over the corresponding oral vowel symbol The fricatives not used in English are actually used by various other languages voiceless bilabial, voiced bilabial, voiceless velar, voiced velar, and voiced glottal NonEnglish affricates are similar to combinations of other sounds Places of articulation used outside of English: Uvular stops: Produced by making a stop closure between the back of the tongue and the uvula Pharyngeal fricatives: Made by opening the jaw wider to pull the tongue back in the mouth Manners of articulation used outside of English: Trills: Different from the English /r/ sound, these are trilled with the tip of the tongue Palatalized nasal: A simultaneous tongue body position for the glide [j] alongside another tongue tip position, indicated by a super script small [j] Velarized alveolar lateral liquid: Like the English [l], but with the tongue body up rather than down, and the tonguetip down rather than up referred to as a dark [l] compared to the tongue body down, tonguetip up clear [l] Glottalized stops (ejectives): Using a different airstream mechanic involving air pressure in the mouth cavity, indicated by a superscript of the glottal stop symbol File 2.5 Suprasegmental features It is often difficult or impossible to identify the quality of a suprasegmental feature without comparing different segments and different utterances Length: Some speech sounds are longer than others by comparison, and long vowels and consonants are indicated by a pair of arrows following the long segments these speech sounds are long only by comparison to their regular "short" pronunciation Intonation: The pattern of pitch movements across a stretch of speech, to change its meaning a rising intonation at the end of an utterance makes it sound like a question, while a falling intonation makes it sound like a statement Pitch accents: A change in fundamental frequency in the middle of an utterance words with a higher/lower pitch than the surrounding words are perceived as very prominent and can change the same string of words to fit different situations Edge tones: A change in fundamental frequency at the end of a phrase, before a perceived break a falling pitch is usually a for a statement (sentencefinal intonation), a rising pitch indicates a

5 LING 1001 Page 5 question (question intonation), and a fall with a slight rise indicates that the speaker is not yet done speaking (continuation rise) Tone: The pitch at which syllables are pronounced can sometimes change a word's meaning in a tone language such as Mandarin there are two types, level (steady tone throughout a syllable) and contour (a single syllable with a tone gliding from one level to another a rising tone or a falling tone) Tones in a tone language are at least somewhat relative, so a given syllable would be high in comparison to other syllables spoken by the same speaker knowledge of the speaker's physical characteristics (gender, height, size) can help to predict this Stress: A stressed syllable is more prominent (longer, louder, and usually contain full vowels) than an unstressed one primary stress is indicated with ['] after a syllable, secondary stress is marked with [,] after a symbol, and tertiary stress is not marked Full vowels are produced with more extreme positions of the tongue, while reduced vowels are pronounced closer to the midcentral position In some languages, stress placement is predictable, but in languages such as Russian and English, stress must be learned for each individual word and can often cause a difference in meaning (bla'ckboard vs black bo'ard a historical feature in schools vs a simple black piece of wood) These suprasegmental features have no meaning or function in isolation, and can only be discovered by comparison of different syllables while the [a] symbol always has a specific meaning, the ['] symbol does not File 2.6 Acoustic phonetics Compression: Air molecules being more crowded than usual Rarefaction: Air molecules being spread farther apart than usual Air molecules have a tendency to stay equidistant from each other, so they move away from/towards each other to return to the equilibrium Periodic wave: A sound wave that repeats at regular intervals, alternately rarefied and compressed at a certain frequency the number of times it repeats per second Sound is produced by air molecule vibration from 2020,000 times per second, yet most of that range is not used in speech telephones stop at 3,500 Hz, but little essential information about the speech signal is lost Complex waves are composed of a number of simple waves interacting with each other this is how speech is formed Fundamental wave: The frequency of the opening and closing of the vocal folds when producing a speech sound Harmonics: Repetitions of the fundamental wave of a speech sound, which have a multiple of the fundamental wave's frequency Fundamental frequency: The first harmonic of a speech sound As a sound wave passes through the vocal tract, the articulators shape or filter the sound, either boosting or damping the harmonic frequencies A speech sound, then, is composed of two things: the source wave (from the vocal folds) and the filter (from the articulators) Acoustic phonetics of vowels: The filtering effect of the vocal tract produces amplitude peaks at certain frequencies by enhancing or damping the harmonics at certain frequencies these peaks are called formants (resonant frequencies of the vocal tract, determined by the length and configuration of the vocal tract) Vowels have several formants, the first three of which are the most important for speech perception these are different from vowel to vowel Plotting the frequencies by their first two formants creates something similar to the vowel chart high vowels have a low F1, while low vowels have a high F1 front vowels have a high F2, and back vowels have a low F2

6 LING 1001 Page 6 Spectrogram: Graphs that encode three acoustic dimensions: the vertical axis represents frequency, the horizontal axis represents time, and the degree of darkness indicates the amount of acoustic energy present at a certain time and at a certain frequency dark horizontal bands usually represent formants Acoustic phonetics of consonants: Stop consonants are characterized by a lack of energy a gap in the display on a spectrogram, reflecting their manner of articulation During a voiced stop, some lowfrequency noise is produced by vibration of the vocal folds, which can be seen on a spectrogram as a dark band at the very bottom during the "silence" of a stop this is called the voice bar Voiceless stops are characterized by a period of aspiration, where air rushes out of the mouth after the release of the stop closure this is transcribed with a superscript [h] The acoustic information about a stop is usually found in the vowels around it, while the tongue glides from one position to the next the formants are in transition towards their usual values The place of articulation of a stop affects the frequency of the F2 at the juncture of the vowel and the consonant around Hz for alveolar stops, low for bilabial stops and higher in the vowel itself, and for velar stops it depends on the vowels preceding and following the consonant Fricatives are created by the aperiodic (random) turbulence of air rushing through a small opening, rather than periodic (repeating) vibration of the vocal folds In English, the relative frequency of fricatives distinguishes them ([s] has a higher frequency than /sh/, is louder than [f], and longer than [z]) Formant transitions can be used to indicate the place of articulation Voiced fricatives combine periodic noise and aperiodic noise, while affricates begin with a gap (for a stop) then the aperiodicity of a fricative For nasals, because the nasal passage serves as the filter for all nasal consonants, their formants are quite similar F1 is usually around 250 Hz, F2 is usually around 2500 Hz, and F3 is usually around 3250 Hz Their place of articulation is still cued by the transition from the nasal into the vowel File 2.7 The phonetics of signed languages Phonetic parameters of signed languages are determined in the same way as those for speech sounds which parameters distinguish one segment from another? Prime: The fundamental element of a signed language, comparable to a phonein a spoken language Unlike phones (which occur sequentially), primes must cooccur with the primes from other parameters to complete the sign this is a function of our visual processing perceiving multiple things at once, which human auditory processing is less suited for Location: Signs can be distinguished by where the sign is produced in the upper half of the face, the lower half of the face, etc. Every sign language has a particular signing space in which signs may be produced, but these places of articulation of relative to whisper, signs are brought in closer towards the signer's center, while yelling is indicated by increasing the signing space and the amount of movement in signs Movement: Two pairs of signs can be distinguished by the amount of movement involved Some signs have movements intended to bring a hand from one place of articulation to another, while others have to do with movement of the wrist or fingers Similar to vowels in spoken languages, a sign could be understood without the movement attached, but it is still a critical part of the articulation of sign languages Handshape: Which fingers are extended, whether the fingers are bent or straight, the position of the thumb, which fingers are touching, etc. One sign can contain more than one handshape Orientation: The direction that the palm of the hands are facing Towards each other, to the left and right, palms downward, etc. Other elements can be incorporated into signing, such as head movement or tilt, and facial expression

7 LING 1001 Page 7 these may be a part of the sign itself, and leaving them out would be performing the sign incorrectly, like leaving a segment out of a spoken word In other cases, face and head movement might act as a suprasegmental feature, a type of "intonation" or emphasis (such as distinguishing HOT and VERY HOT) Where spoken languages have a certain set of consonants and vowels used, signed languages each have their own set of handshapes, movements, and places of articulation not all of which are used in every sign language Some differences are more profound, such as using the elbow as an active articulator in Taiwan Sign Language (in the mouth, the tongue is an active articulator, while the hard palate is a passive articulator because it is used only when your tongue touches it) Much like there are vocal sounds that are never speech sounds, there are many possible arm and hand motions that are simply nonlinguistic or not used in any given language For studying the phonetics of signed languages, video recording is one option, while other sophisticated technologies involve attaching sensors to parts of the signer's hands, arms, face, and so on these sensors record and transfer information to a computer about their position and movement, precisely measuring things such as amount of movement, tilt, orientation, and exact distance between hands and the body Textbook exercises p What are three different areas of phonetics, and how do they fit into the communication chain? p. 88 The three different areas of phonetics are articulatory phonetics, acoustic phonetics, and auditory phonetics. Each represents a portion of the communication chain: articulatory phonetics is the encoding of the message, acoustic phonetics is the transmission of the message, and auditory phonetics is the decoding of the message. 7. Write the phonetic symbol representing each of the following sounds (don't forget to use square brackets). The first one is given as an example. Example: voiced palatal glide: [j] a. Voiceless palatal affricate: [ʧ] b. Voiced velar nasal: [ŋ] c. Voiceless glottal fricative: [h] d. Voiced labiodental fricative: [v] e. Voiced interdental fricative: [ð] f. Voiced palatal fricative: [ʒ] g. Voiced alveolar lateral liquid: [l] 8. Write the threepart articulatory descriptions for the consonant sounds represented by the following symbols. The first one is given as an example. Example: [j]: Voiced palatal glide a. [f]: Voiceless labiodental fricative b. [z]: Voiced alveolar fricative c. [n]: Voiced alveolar nasal d. [ŋ]: Voiced velar nasal e. [ʃ]: Voiceless palatal fricative

8 LING 1001 Page 8 f. [ɹ]: Voiced alveolar retroflex liquid g. [ʒ]: Voiced palatal fricative h. [ʧ]: Voiceless palatal affricate i. [ɡ]: Voiced velar stop j. [ʔ]: Voiceless glottal stop 10. Given the articulatory descriptions of consonants in this file, what would you expect the difference between a [t] and an [s] to look like in static palatography pictures? Of the two pictures below, which do you think could be an instance of [t] and which an instance of [s]? How do you know? What other sounds would make the pattern on the roof of the mouth seen in (a) and (b)? p. 91 The consonant sound [t] is a voiceless alveolar stop, while the consonant sound [s] is a voiceless alveolar fricative. In a stop like [t], there's a complete obstruction of the vocal tract, so the tongue would make a lot of contact with the roof of the mouth. In a fricative like [s], there's a nearly complete obstruction of the vocal tract to produce turbulence, so there'd be just a bit less contact with the roof of the mouth than for a stop. The picture (a) could be an instance of [s], while the picture (b) could be an instance of [t]. The second picture (b) has a lot of contact with the roof of the mouth, so it is probably a stop, which would be [t]. The first picture (a) still has contact with the roof of the mouth, but less than in (b), so it could be a fricative rather than a stop. Another sound that would make the pattern on the roof of the mouth in (a) would be [z], a voiced alveolar fricative, and for (b) it would be [d], a voiced alveolar stop. 14. Write the phonetic symbol representing each of the following sounds (don't forget to use square brackets). The first one is given as an example: Example: High back lax rounded vowel: [ʊ] a. High front tense unrounded vowel: [i] b. Mid back lax unrounded vowel: [ɤ] c. Mid front lax unrounded vowel: [ɛ] d. Low back lax unrounded vowel: [ɑ] p Write the IPA symbol for each of the following sounds (don't forget to use square brackets). The first one is given as an example. Example: Voiced alveolar trill: [r] a. Voiced bilabial fricative: [β] b. Mid front rounded vowel: [ø] c. Voiceless palatal stop: [c] d. Voiceless uvular stop: [ɢ] e. Velarized alveolar lateral liquid: [ɫ] f. Voiceless glottalized alveolar stop: [tˀ] p Match each of the following words to the appropriate spectrogram. a. Shoe b. Hippo

9 LING 1001 Page 9 c. Ow! I) Ow! II) Shoe III) Hippo 38. The following two ASL signs differ in one parameter. Which parameter distinguishes them? THINK vs WONDER When signing for THINK, the location, handshape, and orientation are all the same as when signing for WONDER. But when signing for WONDER, there is also a circular movement with the index finger.