Hoarseness is the most important and often the only symptom of laryngeal disease (Frank, 1940; Zinn, 1945; Palmer, 1956; von Leden, 1958; Caplan, 1960). The importance of mass communications and the evolution of surgical procedures for the improvement of voice have created new interest in the improvement of function studies for the accurate diagnosis of laryngeal diseases and voice disorders. Measurements of laryngeal function may be classified into four main categories: vibratory studies (Oertel, 1985; Moore etc., 1958; Kirikae etc., 1962; Padovan etc., 1975), vocal acoustics (Moore, 1957;Yanagihara, 1962, 1967; Isshiki etc., 1969; von Leden, 1976; Hanson etc., 1979), laryngeal dynamics (Döhne, 1944; Arnold, 1955, 1958; Isshiki etc., 1964; Yanagihara, 1966; von Leden, 1976; Merson, 1979) and neuromuscular tests (Weddel, 1994; Portmann etc., 1955; Hiroto etc., 1962; Kobty, 1975). This multidimensional approach permits a comprehensive image of the vocal function for diagnostic and prognostic studies, medicolegal evaluations, therapeutic determinations, and for applied research in laryngology and phoniatry. In Korea, these studies are yet to be researched, so the author studied the stroboscopic, sonagraphic, aerodynamic, and acoustic investigations of hoarseness due to laryngeal pathology.

Experimental Subjectal and Methods：As experimental subjects, the author selected sixty-five patients, who visited Otolaryngological Department of Yonsei University College on Medicine from Jan. 1979 to Dec. 1980, for hoarseness due to laryngeal pathology and sixty-five healthy subjects, and classified as follow; A) Disease group..65. 1) Inflammation..20. 2) Benign tumor..20. 3) Malignant tumor..10. 4) Vocal cord paralysis..10. 5) Laryngectomee..5. B) Control group..65. The author used the following instruments as experimental materials which have set up at Vocal Dynamics Laboratory in Otolaryngological Department of Yonsei University College of Medicine. 1) Type KS 3, Timcke Stroboscope, 2) Type KAY 6061 B, Sonagraph, 3) Type 6070 A, Contour Display, 4) Type Ampex AG 300-2, Tape Recorder, 5) Type 106 ITT, Microphone, 6) Type 40-1 A, IAC Recording Booth, 7) Type 9L, Collins Respirometer, with the above subjects and instruments, the author has performed the medico-sonagraphic analysis of Korean hoarseness due to laryngeal pathology and the following results were obtained.

Results and Conclusions：1) In inflammation, closure and wave-movement of vocal cords were relatively complete and excellent, respectively, but showing mostly asymmetric amplitude, and, on the other hand, in malignant tumor, the vocal cords showed more asymmetric amplitude, incomplete closure and poor wave-movement than in inflammation and benign tumor. The bowing of vocal cords was observed in all cases of vocal cord paralysis. 2) As the hoarseness increases, the noise distribution extended throughout the harmonic range, resulting harmonic loss or only energy islands, in formants, and the fundamental frequency demonstrates marked irregularities. These changes were more remarkable in low vowels than in high ones. 3) In cases of the mild hoarseness, the decrease of formant's position was occurred only in low vowels, but occurring in all vowels in severe cases, and the position of 2nd formant couldn't be checked in severe cases because of the energy changes of formants. 4) In cases of the mild hoarseness, the widening of formant's width was observed only in low vowels, but observing in all vowels in severe cases, and the width of formants was more widened in the first formant than in the 2nd one. 5) The loss of acoustic energy in formants was not noticed or less than 6 dB in the mild hoarseness, but more than 6 dB in all cases of the severe hoarseness except in inflammation and benign tumor. 6) As the hoarseness increases, the adding noise distribution made the acoustic cues of consonants unremarkable and the phonation time was prolonged. 7) The more hoarseness increases, the more maximum phonation volume and the vocal velocity index decrease respectively and, as the hoarseness increase, the maximum phonation time was more shorter, but increasing mean flow rate. These changes were more remarkable in cases of the vocal cord paralysis. 8) Most cases showed the abnormal speech discrimination scores and, as the hoarseness increases, speech discrimination socres became to be poor. In summing up the above results, the author thinks the main causing factors of the hoarseness are the aperiodicity and the amplitude variations of the fundamental frequency, and the variations in the form of glottal air-pressure impulses. So regularity of the glottal air-pressure impulses and of the vocal cord vibration is a prerequisite for a clear voice. The combined factor of the voice strain and of the loss of laryngeal reflexes due to laryngeal pathology etc. causes the turbulence of glottal air-pressure impulses for the variations of vocal cord vibrations and the closure of the rima glottis, resulting hoarseness.