Larynx And Voice: Physiology Of The Larynx Under Daily Stress (1958)

[music] [music] Heat. Heat. >> [music] [music] [cough] [clears throat] >> How often have you done this today to clear your throat? Would you consider this a strain or is it a harmless process? How does it appear to the naked eye? How many other activities do we perform in our daily existence which place strain upon the larynx? singing, laughing, or just talking. Here is the larynx at work. This harsh sound is known as a vocal fry. Can your eye detect the mechanics of its production? >> [music] >> Recognize all of these sounds in isolation. We produce them frequently each day during our ordinary activities. Alternating whisper and voice. Clearing of the throat. Watch the similarity to a cough and laughter. >> [laughter] [laughter] >> In order to study the effect of daily stress upon the structures of the larynx, this equipment was designed for our special ultra slow motion cinematographic investigations. A 5,000watt incandescent lamp is used for illumination. The intensity of the light is regulated by a variable transformer. The light passes through a cooling cell and is concentrated by a system of lenses onto an oblique mirror. From this mirror, the beam is directed to the small lingial mirror and then to the larynx. The image of the larynx in turn is reflected by a special lingial mirror to the camera. A fast tax camera of this type permits exposures of 5,000 frames or pictures a second. This complicated arrangement was designed to photograph the larynx under normal physiologic conditions just as it is examined by indirect laryangoscopy. While the patient takes her place on the mirror, >> the camera is ready for action. And >> during this brief instant, 100 ft of film were exposed. Perhaps this tremendous speed can be demonstrated as a metal ball hits an ordinary light bulb. Not much to it, was there? Now let us examine the same event in ultra slow motion. To bring out these details, the factor of time was stretched more than 200fold. This is 25 times as slow as the usual slow motion pictures of athletic events to which we are accustomed. At such high speeds, only black and white film provides the precision our investigations require. This type of research has permitted us to present several new concepts of lingial physiology relating to the details of the vibratory cycle to the intensity and frequency of sound production and to the motion of the soft tissues and cartilagages of the larynx. This scene represents normal voice production. The intensity of the sound increases over the 100 ft of film. At this moment, the vocal cords are vibrating 200 times per second. Note the rapid opening phase while the voice is weak and the short period of approximation. This observation conforms to the traditional picture of the vibratory wave. The information may be presented graphically with the vertical axis indicating the glottle width in percentage and the horizontal axis representing time as measured by the individual film frames. Note the rapid opening phase, the slow closure and the brief period of approximation. The limitation of this finding which has been accepted as a basic physiologic principle is revealed when we examine the latter part of the same film strip here. At loud voice, the reverse ratio may be observed. The closing phase of the vibratory wave is now shorter than the opening phase and the period of approximation has increased substantially. Returning to the graphic analysis, the superimposed graph pictures one cycle toward the end of our last scene. Note the contrast between the periods of approximation with weak and loud voice which has also been observed on strososcopic examination. Now note the reversed ratio between opening and closing phases which is presented as a new physiologic concept. This finding accounts for the hitherto unexplained and contrasting results from different acoustic and physical tests. Extensive cinematographic observations on different subjects at different times confirm this phenomenon. This sequence shows the same observations in another patient in reverse order, a decrescendo. This first strip from the beginning of the film where the voice is loud again demonstrates the relatively long opening phase, brief closure and prolonged approximation. The latter part of the same film strip at low intensity. By contrast, note here the short opening phase, prolonged closure and brief approximation. Further experiments indicate this is the result of two interacting forces. First, tension of muscles and ligaments in the larynx which was apparent in the previous film strips and second the pressure of the air column activating the cords. Observe the looseness of all structures in this type of easy voice production. On the corresponding graph, compare the rapid opening phase with the extremely long closing phase. There is no complete approximation. These graphs were prepared by our associate Dr. Timky from our motion pictures. Now note the change in this pattern when the air pressure is increased by a sudden push on the abdomen. With the release of the pressure, the lingial structures return rapidly to their former vibratory pattern. Watch the thick double lip at the free margin of the vocal cords which we have recorded in previous motion pictures. This intricate pattern is well illustrated in this scene at low frequency. The mucous membrane covering the vocal cords appears to trail the movement of the underlying muscles. It is apparent from these pictures that in many patients the loose connective tissue between these two layers extends farther laterally and inferiorly than is generally assumed in the production of voice. Various lingial adjustments are employed to vary the pitch and quality. Singers refer to these fundamental adjustments as registers. We have attempted to record the same pitch using two different physiologic mechanisms. The first scene portrays the chest register of a young man at a frequency of about 175 cycles. Note the contrast as the same individual reproduces almost the same pitch in the so-called head register. The two graphs demonstrate the differences in the vibratory cycles. In the chest voice, we find a long period of approximation, whereas the head voice shows but a momentary contact. As expected, the relation of the opening and closing phases remains the same at similar intensities. In falsetto, the vibrations are much faster and there is even less contact between the vocal cords. In some voices, only the anterior segment of the chords appears to move at very high pitch. Many interesting details may be observed by a slow motion study of the vibratory pattern. Observe the rotary motion of the ligamentum vocali in this patient at low pitch. Could the undulating waves spreading laterally across the chords explain the mysterious waves sometimes noted on stroscopic examination? Other waves appear to travel in anterior and posterior directions as the vocal cords open and close. This longitudinal undulation is related to the pressure applied to different areas of the vocal cords. One of our collaborators, Dr. Sven Smith, has constructed artificial models to demonstrate this phenomenon. In this particular model, more pressure was exerted on one side, resulting in a typical longitudinal wave passing from one end to the other and back again during each vibratory cycle. If the two cords are weighted unevenly, asynchrony of vibration results. In this instance, the uneven weight was provided by the heavy concentration of mucus on one cord. Many other interesting phenomena will be observed on further study. Unfortunately, the scope of this film restricts the extent of our comments. Note here the involvement of all lingial structures in ordinary sound production. Observe the movement of the highlights not only on the vocal cords but also on the ventricular bands in the aritenoid area and even in the purform sinuses. In this particular instance, these highlights reflect not only the vibratory frequency of the vocal cords but also the modulations of the vibatto in an accomplished singer. Our own larynx shows the same total involvement during the stress of daily life. How many times each day do we abuse our vocal mechanism in this manner? The violent oscillations of the lingial structures resemble a fragile object in the throws of a violent storm. hardly cause for amusement. Now we enter the inhalation phase of the laughter which is illustrative of lingial strider. Let us compare the ordinary respiratory pattern with the vibration produced on inhalation. Here the normal exhalation sound is coming to an end and the lingial structures undergo the necessary readjustment. As the direction of the airirstream is reversed, the chords come to a brief standill. Resumption of phonation this time on inhalation presents an entirely different picture. Does the extension of the vibratory wave laterally give a clue to what might be observed from beneath the chords during normal phonation? Graphically speaking, in inspiratory sound production, the opening phase is extraordinarily long. The closing phase extremely brief while the period of approximation takes up about onethird of the vibratory cycle. Even a light cough or clearing of the throat [clears throat] causes havoc in the larynx. This scene is included principally to show the movement of the supragotic structures particularly the epiglotus. During the course of this brief exertion, the rim of the epiglotus actually strikes the posterior wall of the hypotharings, then recoils rapidly in a peculiar compound curve. We have measured the time of this maneuver and found it to be less than 3,000 of a second speed even in our jet age. To a much lesser extent, a similar process may be observed frequently when a vowel is initiated during ordinary conversation. Again we observe a constriction of all the lingial structures. If this constriction is increased sufficiently as in a sharp staccato, a new and different phenomenon may be observed. Here is this peculiar pattern produced in a sustained manner which is sometimes referred to as a vocal fry. Remember what you visualized at normal speed at the beginning of this film. Now watch what really happens. The vocal cords beat in a syncopated rhythm with a long closed phase following every second beat. What a novel and extraordinary configuration. This graph illustrates this bifphasic pattern. The two peaks follow each other in rapid succession while the closed phase takes up almost 1/2 of the total bifphasic cycle. Acoustic measurements of the voice reveal a subharmonic of 75 cycles per second, 1/2 the fundamental frequency of the sound produced. The same film strip also shows another unusual movement. This one in the longitudinal direction. Instead of the usual pattern, there is an elliptical opening traveling from the aritenoid area to the anterior commissur as part of each vibratory cycle. Here is the same bifphasic cycle in another person with a completely normal voice. This phenomenon can be observed only by ultra high-speed photography. It has not been reported previously. Further research will be required to determine the underlying acoustic and physiologic factors. Dr. Smith has tried to explain the mechanics of this shift aerodynamically with a special model. This view presents a sagittal section through the sound producing area. Observe the extensive vibratory motion progressing up the walls of the airway and also the bifphasic beat at the superior aperture. Here are examples of various models used in this film. The central rubber tube of the large model is weighted on each side by foam rubber and slit in the center for cross-sectional observation. The smaller tubes are activated by blowing and are photographed from the distal end. Pitch and quality can be regulated by tension and finger pressure. Ultra high-speed photography of the larynx has uncovered new information on normal lenial physiology under daily stress. With this basis, the research can be extended to the physiology of the abnormal larynx. [music] That's good. >> [music]