Frøkjær-Jensen, Børge

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9 COMPARISON BETWEEN A FABRE GLOTTOGRAPH AND A PHOTO-ELECTRIC GLOTTOGRAPH Berge FrokJer-Jensen 1. Introduction. In this article are published a few preliminary results from the test 0£ our Fabre Glottograph and comparisons between our photo-electric glottograph and the Fabre Glottograph. Glottograms 0£ most 0£ the Danish ·consonants are comp~red with the airflow curves and the oscillograms, and the three-dimen-sionaltype of vocal cord oscillation is shown by ·comparing the curves from the two types of glottographs. *) 1.1. Airflow registration. Some simultaneous recordings 0£ the airflow (trace no.1), the electric impedance 0£· glottis (trace no.2), the square area 0£ the glottis (trace no.3), and the aco~stic oscillogram (trace no.4) have been made £or this article. The airflow recordings are·made by means 0£ the Electro Aerometer and show the outlet airflow measured in volume unit per time unit (cmJ/sec.), - the instrument can be exactly calibrated but has not been calibrated £or the illustrations in this article. A raising 0£ the airflow ' . trace in the recordings means that the outlet airflow is increased. 1.2. Photo-electric glottogram. The photo-ele.ctric glottogram shows the square area between the vocal cords in a horiz~ntal plane. The photo-electric glottograms have a weli defined zero level for closed glottis. However, the glottis may sometimes be closed though the zero level in the glottogram trace nas not been reached, this is because 0£ a certain degree of transillumination 0£ the closed glottis which can be observed especially in the head register. With some subjects we have experienced trouble when• inserting the plastic tube with the photo transistor (light • *) Both types of glottographs.and the Electro Aerometer used for this article .are manufactured for sale by B. Frekjmr-Jensen, Veatre Paradisvej 46, 2840 Holte, Denmark. 10 transducer) through the nose down into the pharynx. We have to a great extent overcome this problem by mounting the trans-ducer in a 2 mm p1astic tube and by g1ueing the £ree end 0£ the transducer to the tube by means of liquid plastic mass. Further-more, both a small lense in ·the end of the photo transistor and the black painting of the transistor has been removed. These improvements of the transducer makes it easier to insert it through the nostrils without much inconvenience. The trans-ducer may be inserted in position in the pharynx and fixed out-side the nose by means of a piece of court plaster. Thus fixed it can be used for hours without discomfort and without disturb-ing the articulation (no local anaesthesia is necessary). It is also possibl~ to pick up the light in the pharynx without· serious interference from the articulatory movements. Only when articulating the most open vowels[a:] and[~:] the back tongue and the epiglottis push the photo transistor out of position. These vowels can, therefore, normally not be recorded by the photo-electric glottograph. 1,3. The Fabre Glottograph, The Fabre Glottograph shows the electric contact area between· the vocal cords in a vertical plane. However, different articulatory movements of the pharynx and of the larynx may influence the electric impedance between the electrodes, as pointed out earlier (J). These unde~irable physiological changes cause a very jumpy zero line which is difficult to stabilize in the registration range of the recorder. Our glottograph has therefore been provided with four different outputs, two of which have different time constants ( 25 mse.c. and 4 sec.) for stabilizing the zero line during articulation (6). (These outputs have not been provided for the glottograms shown in this article,) Some few subjects see_ms to have a throat unfitted for electric impedance measurements because of too much fat ,which results in a bad signal-to-noise ratio, The same.sort of noise disturbance of the glottograms may be observed if ·the electrical contact between the skin and the electrodes is insufficient. Therefore we always µse electrically-conducting jelly between C D Speed, 100 mm/sec. 11 r t,'.J, ,,/"-\ 111 Jt' • \ Fig. ··1. i 1-1 I I A: Airflow curve B: Photo-electric glottogram C: Fabre glottogram D: 0scillogram 12 the electrodes and the skin. The oval electrodes used for the· glottograms shown below were a little less than 2 cm2 each, but further experiments have to be done in order to investigate the influence of different shap~s and areas of the electrodes. 1.4, The oscillogram. A normal oscillogram has been recorded by means of a microphone capsula mounted inside the aerometer mask. The frequency response of the microphone has been electricaliy_ changed in order to cancel out the acoustic resonances of the aerometer mask (tube system). The microphone may thus be used for simultaneous tape recordings for sonagrams or other acoustic analyses. 2. Danish tenues and mediae. The _table Fig. 1 shows the in nonsense context: [EpE], [ctaJ [ci&]. As earlier stated (1), (2) Danish consonants ptk and bdg , [ck~] , and [c~c], [c~c], the main difference between Danish tenues ptk and Danish mediae bdg is one of aspiration. This is shown very clearly in the airflow curve and the glotto-grams. The mean duration of the aspiration in the tenues in the examples shown in Fig. 1 is about 7 csec., whereas the mean duration of the aspiration in the·mediae is only about 1.5 csec. If we compare the moment of explosion (airflow curve) in the tenues with the glottis opening (both types of glottograms) we may observe that the explosion in the tenues is situated in the opening phase of glottis, which means that the aspiration .~s syncronized wi~h the maximum opening of glottis.· - With some speakers the explosion phase seems rather to coincide with the maximum opening, see the curves in reference (J). - On the other hand the curves of mediae show that the moment of explosion in bdg is situated in the closing phase of glottis; which conditions that ~hly a lit~le amount of air is left for a possible: aspiration. Fig. 1 thus very clearly proves that the main difference between the Danish ptk and bdg {'based on 256 examples for only one speaker BFJ) is one of opening glottis during the ptk·i- stop cl_osur~ and fully open glottis during the ptk-aspiration versus med:!:~m --~!?_en. _g~~ __ tt_i~-- dt:11:'il:lg -~~e _ bdg-s_top closure followed . _____ _ f e s • Speed: 100 mm/sec. l 1 Fig. lJ ;8 2 •. A: B: C: D: Airflow curve Photo-electric glottogram Fabre glottogram Oscillogram 14 by closing glottis in the bdg-explosion phase. ( Compar_e the results in references (4) and (7)). Due to the different registration methods, the photo-electric glottograph seems to illustrate in a better way what happens during the opening phase of the glottis, whereas the Fabre Glottograph probably rather illustrates what happens during the closing phase in the vertical contact area between the mucous membrane of the v~cal cords (compare the two giotto-gram traces_during the closure between the words.). 3. Danish [ f J and [ s] • In Fig. 2 a very interesting difference between [f] and [s] is seen in the ,two glottograms. The Fabre Glottograph shows a greater electric- impedance of the glottis for [s] than for [f] (which s4ould indicate a more open glottis for [s] ), whereas the opposite is seen in the photo-electric glottograms, which normally show a greater opening for [f] than for [s] • This· difference between the two glottographic methods in the registration of [f] and [s] is ~uite constant for this s~bject. Further investigations have to be made before a possible hypo-thesis concerning the difference between the glottal articulations of [f] and [s] can be advanced. 4. The voiced consonants. Fig. 2 also shows some examples of voiced consonants. Especially the Danish[~] shows the difference of phonation between voiced consonants and surrounding vowels. The elec.tric impedance of the glottis is considerably raised during the <-r: articulation of·[~], i.e. the contact area between the.mucous membranes of the vocal cords in the vertical plane is reduced. However, the photo-electric glottogram does not show such a -change in phonatory conditions (see the article in this report! Fourier Analyses of Photo-electric Gl~ttograms). Once again we may c~nclude that the two ~ypes·of glottographs deliver two different e~t-s of parameters concerning the working conditions of the human larynx • ....... 15 Photo-electric glottogram. Fabre glottogram. (electric impedance) Vowel[~ij, spoken by subject BFJ. Chest ·register, medium voice effort, fundamental frequency 120 cps. Fig. J. 5. Recordings of the primary voice source cycle. Fig. J shows a polaroid photo of simultaneous recordings made by the tw~ glottographs. The photo is a good illustration ·of how we can get information· a.bout the three-dimensional opening and closing movements of glottis. If we compare the slope of the glottal cycle in the Fabre glottogFam (the lower ~!ace) with the photo-electric glottogram we can only explain the different forms of the two simultaneously recorded curves by assuming the explosions (excitations) ~s a slowly opening movement starting from below and moving upwards. When it reaches the edges the v~cal cords open up and we get in the upper curve a registration'of the opening area. When the glottis closes the Fabre glottogram shows that the two mucous . membranes in the vertical plane suddenly come into touching contact with each other, i.e. we have a gradually opening and a suddenly closing movement. This function of the primary voice is ·typical for the chest register (8), (9), which operates both in the vertical and the horizontal plane. Recordings of the typical head register function do not show this three-dimensional type of oscillation. 16 Acknowledgement. The construction of the two glottographs has been supported by "Statens Almindelige Videnskabs:fond" (the Danish State Research Foundation). - -· --- -----References. ( 1 ) (2) Eli Fischer-J0rgensen, "Acoustic Analysis of $top Consonants", Miscellanea Phonetica. II(1954), pp.42-59. Eli Fischer-J0rgensen, "Phonetic Analysi·s of Danish Stop Consonants", ARIPUC. _U 19.66); pp~ J1-JJ. (J) Eli Fischer-J0rgensen, B. Fr0kjrer-Jensen, and J. Rischel, (4) (5) (6) (7) (8) (9) 1 "Preliminary Experiments with the Fabre Glottograph", ARIPUC ' 1 ( 1966), pp .• 22-J 1. L. Lisker, A.S. Abramson, F.S. Cooper, and M.H. Schwey, "Transillumination of the Larynx in Running Speech", Status Report on Speech Research SR-5/6(1966), Haskins Laboratories. c. van Michel, "Les Artefacts en Glottographie", Revue Electro Diagnostic Therapie 4(1967). Jana Ondrackova, "Glottographical Research in C_zech Sound Groups", Zei tschrift fur Phonet•ik S rachwissenschaft und . Kommunikationsforschung, Band 21, Hft.1 2 1968 , pp~145-152. I.H. Slis and P.-H. Damste, "Transillumination of the Glottis during Voiced and Voiceless Consonants", Annual Progress Report 2(1967), IPO, Eindhoven. . Svend Smith,-· "Remarks on the ·Physiology of the Vibrations of the Vocal Cords", Folia Phoniatrica 6(1954), pp. 166-178. Svend Smith, "Vertikale Komponenten bei der Funktion der Stimmlippen", Phonetica 11(1964), PP• 24J-247. 

Comparison between a Fabre Glottograph and a Photo-Electric Glottograph

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Comparison between a Fabre Glottograph and a Photo-Electric Glottograph

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