Proceedings Fonetik 2009 - Institutionen för lingvistik

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Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm UniversityF0 lowering, creaky voice, and glottal stop: Jan Gauffin’saccount of how the larynx works in speechBjörn LindblomDepartment of Linguistics, Stockholm UniversityAbstractF0 lowering, creaky voice, Danish stød andglottal stops may at first seem like a group ofonly vaguely related phenomena. However, atheory proposed by Jan Gauffin (JG) almostforty years ago puts them on a continuum ofsupralaryngeal constriction. The purpose of thepresent remarks is to briefly review JG:s workand to summarize evidence from current researchthat tends to reinforce many of his observationsand lend strong support to his viewof how the larynx is used in speech. In a companionpaper at this conference, Tomas Riadpresents a historical and dialectal account ofrelationships among low tones, creak and stødin Swedish and Danish that suggests that thedevelopment of these phenomena may derivefrom a common phonetic mechanism. JG:s supralaryngealconstriction dimension with F0lowering ⇔ creak ⇔ glottal stop appears likea plausible candidate for such a mechanism.How is F0 lowered?In his handbook chapter on “Investigating thephysiology of laryngeal structures” Hirose(1997:134) states: “Although the mechanism ofpitch elevation seems quite clear, the mechanismof pitch lowering is not so straightforward.The contribution of the extrinsic laryngeal musclessuch as sternohyoid is assumed to be significant,but their activity often appears to be aresponse to, rather than the cause of, a changein conditions. The activity does not occur priorto the physical effects of pitch change.”Honda (1995) presents a detailed review ofthe mechanisms of F0 control mentioning severalstudies of the role of the extrinsic laryngealmuscles motivated by the fact that F0 loweringis often accompanied by larynx lowering. Howeverhis conclusion comes close to that of Hirose.At the end of the sixties Jan Gauffin beganhis experimental work on laryngeal mechanisms.As we return to his work today we willsee that, not only did he acknowledge the incompletenessof our understanding of F0 lowering,he also tried to do something about it.Jan Gauffin’s accountJG collaborated with Osamu Fujimura at RILPat the University of Tokyo. There he had an opportunityto make films of the vocal folds usingfiber optics. His data came mostly from Swedishsubjects. He examined laryngeal behaviorduring glottal stops and with particular attentionto the control of voice quality. Swedishword accents provided an opportunity to investigatethe laryngeal correlates of F0 changes(Lindqvist-Gauffin 1969, 1972).Analyzing the laryngoscopic images JG becameconvinced that laryngeal behavior inspeech involves anatomical structures not onlyat the glottal level but also above it. He becameparticularly interested in the mechanism knownas the ‘aryepiglottic sphincter’. The evidencestrongly suggested that this supraglottal structureplays a significant role in speech, both inarticulation and in phonation. [Strictly speakingthe ‘ary-epiglottic sphincter’ is not a circularmuscle system. It invokes several muscularcomponents whose joint action can functionallybe said to be ‘sphincter-like’.]In the literature on comparative anatomy JGdiscovered the use of the larynx in protectingthe lungs and the lower airways and its keyroles in respiration and phonation (Negus1949). The throat forms a three-tiered structurewith valves at three levels (Pressman 1954):The aryepiglottic folds, ventricular folds andthe true vocal folds. JG found that protectiveclosure is brought about by invoking the “aryepiglotticmuscles, oblique arytenoid muscles,and the thyroepiglottic muscles. The closureoccurs above the glottis and is made betweenthe tubercle of the epiglottis, the cuneiform cartilages,and the arytenoid cartilages”.An overall picture started to emerge bothfrom established facts and from data that he gatheredhimself. He concluded that the traditionalview of the function of the larynx in speechneeded modification. The information conveyedby the fiberoptic data told him that in speech8
Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm Universitythe larynx appears to be constricted in twoways: at the vocal folds and at the aryepiglotticfolds. He hypothesized that the two levels “areindependent at a motor command level and thatdifferent combinations of them may be used asphonatory types of laryngeal articulations indifferent languages”. Figure 1 presents JG’s 2-dimensional model applied to selected phonationtypes.In the sixties the standard description ofphonation types was the one proposed by Ladefoged(1967) which placed nine distinct phonationtypes along a single dimension.In JG’s account a third dimension was alsoenvisioned with the vocalis muscles operatingfor pitch control in a manner independent ofglottal abduction and laryngealization.Figure 1. 2-D account of selected phonation types(Lindqvist-Gauffin 1972). Activity of the vocalismuscles adds a third dimension for pitch controlwhich is independent of adduction/abduction andlaryngealization.JG’s proposal was novel in several respects:Figure 2. Sequence of images of laryngeal movementsfrom deep inspiration to the beginning ofphonation. Time runs in a zig-zag manner from topto bottom of the figure. Phonation begins at thelower right of the matrix. It is preceded by a glottalstop which is seen to involve a supraglottal constriction.Not only does the aryepiglottic sphincter mechanismreduce the inlet of the larynx. It alsoparticipates in decreasing the distance betweenarytenoids and the tubercle of the epiglottis thusshortening and thickening the vocal folds.When combined with adducted vocal folds thisaction results in lower and irregular glottal vibrationsin other words, in lower F0 and increaky voice.(i)(ii)(iii)(iv)There is more going on than mere adjustmentsof vocal folds along a singleadduction-abduction continuum: Thesupralaryngeal (aryepiglottic sphincter)structures are involved in both phonatoryand articulatory speech gestures;These supralaryngeal movements createa dimension of ‘laryngeal constriction’.They play a key role in the productionof the phonation types of the languagesof the world.Fiberoptic observations show that laryngealizationis used to lower the fundamentalfrequency.The glottal stop, creaky voice and F0lowering differ in terms of degree of laryngealconstriction.Figure 3. Laryngeal states during the productionhigh and low fundamental frequencies and with thevocal folds adducted and abducted. It is evident thatthe low pitch is associated with greater constrictionat the aryepiglottic level in both cases.9
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