Electromagnetic articulography

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Attached sensors for performing an EMA measurement
Possible arrangement of the sensors in the sagittal plane

The electromagnetic articulography or -grafie (short EMA ) is a method for studying the oral motor skills in speaking and swallowing , which was first described in the 1971st It allows a continuous spatial and temporal recording of the tongue , lip and jaw movements of a patient or test person and is therefore mainly used in the context of orthodontic diagnostics and for the analysis of lingual speech movements.

application

functionality

By means of inductive distance measurement, the positions of individual receiver coils (sensors with a diameter of about 3 mm) attached at any point on the articulation organs can be determined with comparatively high accuracy for the duration of an utterance and then displayed in a two- or three-dimensional Cartesian coordinate system . For this purpose, alternating electromagnetic fields are used, which are generated by at least three (originally two) transmitter coils attached to the area around the head - mostly on a helmet-like construction. In order to record the speech movements, the distance between the sensors and these transmitter coils is now continuously calculated within this magnetic field. The mounting of these sensors is carried out in varying numbers at a distance of at least 10 mm in most cases at upper and lower lip , the upper respectively lower jaw as well as to the tongue tip , -sheet and back have , more rarely, on the palate or to the incisors .

evaluation

Graphic representation of tongue movements in three-dimensional space

The graphic display form resulting from the measurement can then be evaluated and analyzed together with the audio track recorded at the same time by a microphone on the computer with regard to the motor skills of the organs involved in the speech process, in order to be able to identify and specifically treat dysgnathias or other oral malfunctions. The accuracy of the measurement in the electromagnetic field is around 0.5 mm. If one or more coils twist or shift during the recording, a correction on the computer is possible.

A major advantage over other common examination methods, such as electropalatography , is the permanent visibility of the tongue position, regardless of whether there is a constriction at the point of articulation or not (such as with vowels, for example ). Oral attachment of the sensors can sometimes be speech-impairing and uncomfortable for the patient, the average field strength of the measuring field is a maximum of 1.7 µT ( microtesla ), however, in a range that is harmless to human health, which, in contrast to examinations with fluoroscopy, is also longer Enables recording sessions.

Further research areas

In phonetics , this method is used to statements about the effects of aerodynamics , biomechanics , linguistics to meet and motor skills on the observable speech movement. Furthermore, possibilities have been researched here since 1993 to be able to map the measurement results , which were previously limited to the mediosagittal plane , also in three dimensions in the future, which was achieved for the first time in 2008 in a slightly different experimental arrangement with the electromagnetic articulograph AG500 from Carstens Medizinelektronik GmbH . This method is now established in science and diagnostics and has largely replaced the similarly precise variant with a two-dimensional form of representation.

literature

  • Paul Walter Schönle: Electromagnetic articulography: a new method for the clinical examination of speech motor skills . Springer, Berlin 1988, ISBN 3-540-50071-5 .

swell

  1. ^ Catriona Steele, Pascal Van Lieshout: Use of Electromagnetic Midsagittal Articulography in the Study of Swallowing . In: Journal of speech, language, and hearing research . tape 47 , 2004, p. 342-352 , doi : 10.1044 / 1092-4388 (2004/027) (English).
  2. ↑ a b c Philip Hoole: Use of electromagnetic articulography in the analysis of lingual speech movements . In: Vevi Hahn (Ed.): Schauplatz Mund: The orofacial system as a sensorimotor unit . Working group for myofunctional therapy, Munich 1999, ISBN 3-00-004121-4 , p. 101-114 ( [1] [PDF]).
  3. ↑ Thomas J. Hixon: An Electromagnetic Method for Transducing Jaw Movements during Speech . In: The Journal of the Acoustical Society of America . tape 49 . Acoustical Society of America , 1971, ISSN  0001-4966 , pp. 603-606 (English).
  4. ↑ a b R. Schwestka-Polly, W. Engelke, D. Engelke: Importance of electromagnetic articulography in the investigation of the motor tongue function in the context of orthodontic diagnostics . In: Advances in Orthodontics . tape 53 . Springer, Berlin / Heidelberg 1992, p. 3-10 , doi : 10.1007 / BF02165139 .
  5. ^ Computer Vision, Speech Communication & Signal Processing Group: Audiovisual Speech Inversion. National Technical University of Athens , accessed August 23, 2020 .
  6. ^ Philip Hoole, Noel Nguyen: Electromagnetic articulography in coarticulation research . In: Wiallam Hardcastle, Nigel Hewlett (Eds.): Coarticulation: Theory, Data and Techniques . Cambridge University Press, Cambridge et al. 1999, ISBN 0-521-44027-0 , pp. 260-269 (English, [2] [PDF]).
  7. ^ Yana Yunusova, Jordan R. Green, Antje Mefferd: Accuracy Assessment for AG500, Electromagnetic Articulograph . In: Journal of Speech, Language, and Hearing Research . tape 52 . American Speech-Language-Hearing Association, 2009, p. 547-555 , doi : 10.1044 / 1092-4388 (2008 / 07-0218) (English).