Stroboscopy of the larynx

Stroboscopy of the larynx is one of the most important methods of studying the movements of the vocal folds, allowing you to visualize their natural movements in an adequate for visual perception.

Modern technical means used for stroboscopy of the larynx allow "slowing down" the visible movement of the vocal folds, "stopping" them in any phase of motion, registering these movements with video equipment, followed by detailed analysis.

The phenomenon of stroboscopy was discovered in 1823 by the French physicist J. Plateau and independently of him in 1833 by the German scientist S. Stampfer. In 1878, the French laryngologist M.Ortel (M.Ortel) for the first time performed a stroboscopic examination of the larynx with an indirect laryngoscopy using the Garcia mirror.

In recent years, in connection with the new technological developments of the Danish company Vruel and Kjaer, which produces multi-purpose video stroboscopes, the problem of stroboscopy of the larynx has been further developed. It should be noted, however, that the essence of the method of stroboscopy is not something that is changing the very movement of the vocal folds, since this is impossible in principle. The method is based solely on the physiological properties of the organ of vision and the corresponding light effects that make it possible to fragment the picture of movements of the vocal folds and adapt it to the physiological capabilities of the human eye.

The stroboscopic effect is the result of a purely physiological phenomenon manifested in the visual system of the observer, a kind of visual illusion that arises with periodic illumination of a continuously moving object.

The essence of illusion lies in the fact that the observer sees this object moving as if in jumps, because the intermediate movement of the object between these jumps drops out of the perception of the overall picture of smooth motion due to the periodic absence of illumination of the object of observation. The perception of motion by jumps occurs when the periods of absence of illumination are large enough and exceed such a physiological phenomenon for the organ of vision as the critical frequency of fusion of light flashes. The fact is that the visual perception is characterized by a certain inertia, manifested in the fact that after the exposure of a stationary object, for example by means of a flash of light, the observer "sees" this object in the absence of illumination for another 0.143 s, after which this image disappears. If the ignition time is more than 0.143 s, then the object will periodically appear and disappear, if the frequency of light flashes turns out to be such that the period of ignorance is less than the specified value, then the object will be perceived as constantly illuminated, i.e. Its perception will be continuous.

The foregoing is also true for a moving object, with the only difference being that in the period of darkening the object manages to move to a new location, and if the period of displacement is greater than 0.1 s, the movement of the object will be perceived as abrupt, if less - then smooth, continuous.

Thus, the smoothness or discontinuity of the movement of an object during its periodic illumination depends on the frequency of light flashes and on the inertness of the organ of vision, which preserves the seen picture for 0.1 s. By changing the frequency of illumination of a moving object, it is possible to obtain several types of stroboscopic effect - slow motion forward (towards the actual motion); effect of immobility of the object; delayed backward movement, etc. You can also get the effect of a jumplike movement forward or backward, but for this it is necessary that the period of ignorance be greater than 0.1 s.

Laryngostroboscopic examination of the larynx is carried out with the help of special devices called stroboscopes. Modern stroboscopic instruments are divided into mechanical or optical-mechanical, electronic and oscillographic. In medical practice in the last decade of the XX century. Video-stroboscopic installations with wide multifunctional capabilities were widely used.

With pathological conditions of the vocal apparatus, various stroboscopic pictures can be observed. When assessing these pictures, it is necessary to take into account the level of the position of the vocal folds, the synchrony and symmetry (mirroring) of their oscillations, the nature of their interlocking and the timbre of the voice. Modern video stroboscopes allow you to record in the dynamics of the stroboscopic picture of the larynx simultaneously with the background sound and then perform a careful correlation analysis between the movement of the vocal folds and the frequency characteristics of the sounding voice.

Normally, when stroboscopic, the vocal folds are visualized at the same level. With some diseases, most often of a functional nature, the vocal folds are located at different levels, with the higher situated one seems the more affected fold.

This phenomenon is revealed only in stroboscopy, which also allows us to identify the so-called knots of vibrations of the vocal folds, i.e., areas that shift with the maximum amplitude. It is in these areas that singers or teachers form so-called singing knots. With the help of stroboscopy it is possible to differentiate the movements of the vocal folds in character and shape, i.e., whether they oscillate all the way or only partially, the front or rear sections, the entire mass or only the free edge,

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