Laryngograph

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Laryngogram (or electroglottogram) of an unvoiced consonant in a voiced environment

The laryngograph (also known as electroglottograph or EGG ) is a device that is used to record and examine vocal folds vibrations in phoniatrics , ear, nose and throat medicine , speech therapy and phonetics . Both "Laryngograph" and (English) "Electroglottograph" are trade names, the first going back to a British manufacturer, the second to an American.

Two electrodes that are placed on the neck at the level of the thyroid cartilage send a high-frequency current of around 5 volts. The resistance between the two electrodes is subject to constant fluctuations, caused by head and larynx movements as well as vocal folds. In this way the electrical voltage is modulated ( amplitude modulation ). The vocal cord vibration increases the resistance when the vocal cord opens and decreases when the vocal cord closes. After demodulation of the signal waveform representing the periodic variations in resistance during the vocal fold activity remains.

Using the laryngogram (or electroglottogram), as the signal is called, the frequency of the vocal folds vibrations can be read. Since disturbances in the vocal cord function are reflected as deviations from the normal waveform, the signal can be used to diagnose diseases. The device is also used in speech training for deaf people, as the vocal folds can be followed on the screen while they are speaking. In phonetics , the device is applied, for example to the vocal fold activity during articulation study of speech sounds. The method of laryngography, as the use of the laryngograph is called, was developed in the 1950s by the French Fabre and later further developed by the Danes Frøkjær-Jensen and Thorvaldsen (1960s) and the British Abberton and Fourcin (1970s).

Compared to other examination methods, such as stroboscopy , laryngography has the advantage that it is non-invasive and only requires a laryngograph and a PC to be used. The disadvantage, however, is that the signal requires a high-pass filter which largely filters out the low-frequency fluctuations in resistance, such as those caused by movements of the larynx. The modulation of the high-frequency signal, which can be traced back to the vocal fold activity, is affected to a certain extent by the filter, which means that information about the duration of the vocal fold contact can be lost.

terminology

  • The method of recording vocal fold vibrations described above is called electroglottography or laryngography .
  • A common abbreviation for recording, the laryngogram is Lx , while the electroglottogram - just like the procedure itself and like the electroglottograph recording device - is sometimes shortened to EGG .

Individual evidence

  1. ↑ P. Fabre: Un procédé électrique percutané d'inscription de l'accolement glottique au cours de la phonation. Glottographie de haute fréquence. Premiers results. In: Bulletin de l'Académie Nationale de Médecine. Vol. 141, 1957, ISSN  0001-4079 , pp. 66-69.
  2. ^ B. Frøkjær-Jensen, P. Thorvaldsen: Construction of a Fabre Glottograph. In: Annual Report of the Institute of Phonetics, University of Copenhagen. Vol. 3, 1968, ISSN  0589-6681 , pp. 1-8.
  3. ↑ AJ Fourcin, E. Abberton: First applications of a new Laryngograph. In: Medical and Biological Illustration. Vol. 21, 1971, ISSN  0025-6978 , pp. 172-182.

Web links

Wiktionary: Laryngograph  - explanations of meanings, word origins, synonyms, translations