Harvard Linguistics 110 - Class 06 Lab Phonetics

Linguistics 110 Class 6 (10/7/02)

Zhang/Öztürk/Quinn Laboratory Studies of Phonetics ARTICULATION

(1) Static Palatography: •

Purpose: to study the region of upper surface of vocal tract or tongue contacted for a certain speech sound.

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Method: paint palate OR tongue with mixture of charcoal and olive oil. When tongue touches palate, the coated surface transfers coating to the other surface.

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Palatogram: paint tongue, data from palate. Need mirror.

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Linguogram: paint palate, data from tongue.

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Any precautions? a. If you are interested in the difference in place of articulation between [s] and [S] in English, should you use sop-shop or sot-shot? b. Anything about the vowel contexts?

(2) Dynamic Palatography—Electropalatography (EPG) • • • • •

Subject wears a custom-made pseudo-palate that has electrodes embedded in its surface. When an electrode is contacted, a circuit is completed, current flows, and the contact is recorded. The information is sampled over time (typically 40-200Hz, i.e., every 25-5 msecs) Advantages over static palatography: quantitative, time-varying information. Disadvantages: expensive (around $1,300 per speaker), pseudo palate might alter speech.

(3) Electromagnetic Articulography (EMA) •

Purpose: to track articulator movements over time during speech production using alternating electromagnetic fields.

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Physical principle the device is based on: the electromagnetic field strength in a receiver is inversely proportional to the cube of its distance from a transmitter.

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Method: a. Three transmitter coils placed equidistant from one another so that they generate a radially symmetric alternating electromagnetic field at different frequencies. b. A number of receiver coils (sensors) placed on the subject’s articulators (tongue, jaw, lips and teeth) along the midsagittal plane. c. The induced voltages on receiver coils are sampled at a high frequency.

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d. These voltages provide a measure of each receiver’s distance from each transmitter. e. The Cartesian coordinates of each receiver can be calculated as the point where the radii of three circles from the three transmitters intersect. (4) Other means of studying the vocal tract: • • •

X-ray. Ultrasound. Magnetic Resonance Imaging (MRI).

(5) Articulatory study of the larynx. •

Fiberscopic laryngoscope.

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Electroglottography (EGG). a. Purpose: to study vocal fold behavior such as f0, closed and open quotients, non-invasive. b. Method: place a set of skin electrodes on both sides of the larynx; glottis open → increased impedance; glottis closed → decreased impedance.

AERODYNAMICS (6) Using flow masks to collect aerodynamic data: •

Purpose: to study timing, magnitude or aspiration, nasalization, frication, etc. To infer articulatory information when such information is hard to collect (e.g., movement of velum).

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Method: flow masks (separate masks for oral and nasal, or one mask with split channels). A pressure transducer translates pressure to electrical volt.

ACOUSTICS (7) Source and filter: • •

Source: vocal fold vibration—f0 and high frequencies that are multiples of f0. Filter: vocal tract—amplifies certain frequency components and weakens others depending on its configuration.

(8) Spectrogram and waveform: • •

A spectrogram is a graph representation showing frequency, amplitude and time information. A waveform is a graph showing the amplitude of variation of air pressure of a specific point in a time course.

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