science

Photoglottography

Photoglottography is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photoglottography rather than just read about it. In short: Photoglottography or photo-electric glottography is a laboratory technique for investigating the opening and closing of the glottis in the larynx. It detects variations in the amount of light that can pass through the glottis as it opens and closes.

Key takeaways

Photoglottography belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Photoglottography to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Photoglottography from memory before moving on to harder problems.

Reference excerpt

Photoglottography or photo-electric glottography is a laboratory technique for investigating the opening and closing of the glottis in the larynx. It detects variations in the amount of light that can pass through the glottis as it opens and closes.

Transillumination of the glottis

It was observed by Czermak in 1861 that the inside of the trachea could be illuminated from outside the neck, in what he called illumination by transparency, and the resulting light passing through the glottis observed with a laryngoscopic mirror. Electronic techniques making use of this observation began to be used in the mid-twentieth century. Instruments such as that designed and manufactured by B. Frøkjaer-Jensen, have used the combination of a light source illuminating the trachea from below, and a light-sensitive cell positioned above the glottis in the pharynx to detect light passing through the glottis. This cell is fixed near the end of a thin tube inserted through the nose and nasal passages (which leaves the articulators relatively free to move in speech); in the Frøkjaer-Jensen instrument the tube is extended so that a few centimetres can be swallowed into the oesophagus in order to anchor the light-sensitive cell securely in place. The light from a light source is carried to the neck by a tapered perspex rod pressed against the neck immediately below the thyroid cartilage; alternatively, a cold light source may be applied directly to the neck.

Photoglottography in speech research Two main areas have been explored with this technique.

Examination of vocal fold vibration A number of researchers have attempted to compare the photoglottograph output with measurements of glottal opening based on high-speed or stroboscopic film during phonation. If the two were closely similar, the photoglottograph would represent a quicker and cheaper method of analysis of phonation. However, Baken reports variable results: a study by Coleman and Wendahl concluded that "relating photoglottographic waveforms ... to glottal area is not only hazardous but invalid in many cases", while a later study by Harden found that the photoglottograph provided "essentially the same information on glottal area function as that provided by ultrahigh-speed photography"

Detection of large-scale glottal opening and closing In addition to the study of vocal fold vibratory patterns, the technique may be used to detect the opening of the glottis for voiceless consonants or the closure of the glottis for glottalic consonants and glottal stop.

Clinical applications Photoglottography has been evaluated for usefulness in the study of dysphonic patients in the clinic. The technique is thought to be useful in reflecting the phonatory effect of Parkinson's disease.

Worked examples

Example 1 — a first encounter with Photoglottography

Start with the simplest possible case. Write down what Photoglottography claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photoglottography before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photoglottography ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photoglottography

In research: Photoglottography appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Photoglottography in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Photoglottography is common in secondary-school and first-year university syllabi. It links to neighbouring topics Laboratory techniques, Phonetics, so understanding it makes those chapters shorter.
In everyday life: Look for Photoglottography outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Photoglottography in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Photoglottography means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Photoglottography out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Photoglottography in simple terms?

Why does Photoglottography matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photoglottography?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photoglottography.