都市管給水 및 市販地下水의 弗素이온濃度에 關한 調査硏究

학위논문(석사)--서울대학교 대학원 :치의학과 예방치학전공,1999.Maste

(The) study of reference hearing levels in Koreans

의학과/박사[한글] [영문] Accuracy in determing auditory thresholds is crucial for identifying persons with decreased hearing acuity, particularly in view of the ever-expanding growth of hearing conservation programs, diagnostic clinics and the increased use of industrial audiometry. The results of hearing tests are important in deterring the necessity for medical treatment, educational placement, acceptability for employment and the advisibility of a hearing aid. The accuracy of hearing tests is directly related to a number of factors, such as the training and experience of the operator, environmental noise and the cooperation, and attention of the subject. Of equal importance is the state of calibration of the audiometer. Individuals differ from one another, and normal hearing for the clinician turns out to be a range, not a single value, even for subjects of the same age and sex. So it is required to have standardized reference hearing threshold for normal person, audiometric equipment and procedures. Although American Standards Association (1951) and International Standards Organization (1964) levels have been universally adopted, various world countries have the reference hearing levees of their own. But there are no documents about any standards for reference hearing levels in Koreans with well-calibrated audiometer. The purpose of the present study is an attempt to determine the reference hearing levels in Koreans, and accordingly to contribute to be a fundamental data for the otological research in Korea. In accordance to this study, it is also examined to study about the threshold changes by means of various psychoacoustic audiometric procedures. Test subjects were well-motivated 300 persons from 18 to 24 aged group whose medical history showed no evidence of otologic diseases and other abnormality. The studies were all carried out under carefully controlled conditions of ambient noise and employed up-to-date psychoacoustic method (Hughson-Westlake method). All subjects were tested on 11 frequencies with Maico Model MA-10 audiometer which was calibrated with Bruel & Kjaer Sound Level Meter, artificial ear and mastoid using 3 crosses testing. The results were summarized as follows: 1. Threshold measurements using a descending technique yielded lower (better) threshold by average 1.2 dB than those obtained with an ascending technique. 2. Comparing on the basis of the first and second test, threshold measurements show poorer threshold for the second test at low frequencies below 1000 Hz by average 1.2 dB than those obtained for the first test, bet conversely at high frequencies it shows lower (better) threshold by average 1.8 dB. 3. Generally average 1.5 dB of better threshold through all frequencies was obtained by giving enough instruction for the test. 4. There was no significant difference for threshold measurements between useful finger observation method and button method as a hearing response. 5. The reference hearing threshold in Koreans revealed average 6.7 dB of better threshold than American Standards Association levels, but average 5.2 dB of poorer one than International Standards Organization reference levels. So Korean reference hearing threshold is known to be approximately in median value between ASA and ISO levels.restrictio

The Cariogenic potentiality in the Korean snack foods

학위논문(박사)--서울대학교 대학원 :치의학과 예방치학전공,2002.Docto

(A) clinical audiological survey of noise-induced hearing loss

의학과/석사[한글] [영문] The first recorded noise-induced hearing loss was reported by Alberti in 1951. since Fosbroke reported a survey of hearing loss of factory employees in 1831, a great number of studies have been published in this area. Moreover, in present social development, it has been shown that hearing loss, due to various kinds of noise, is prominent. This is because of the advances in industrial medicine. This has been the cause of one of the medical problems not only in Otolaryngology, but also in society. The main cause of noise-induced hearing loss has been shown to be environmental noise. Also it is related to the duration of exposure, sex and individual susceptibility to such noise. In Korean industry, there has been no adequate protection against such noise. Therefore recently, we have noted an increasing tendency for such hearing loss. So it is very important to consider the degree and severity of the noise-induced hearing loss. the author has done a study concentrating on the occurance, ???? tricity, sex difference and degree of such noise-induced hearing loss according to age and years of service. 2235 employees who work in the various kinds of environmental noise at a fabric factory located in Seoul were used a stest subjects. The 3 step process in each subject included: 1) Complete case histories in 3 parts: background data (residence, military service), aural history (familiarl deafness, illness, accidents), and present hearing status (tinnitus, use of telephone). 2) Otological examination. 3) Preliminary screening hearing test with a pure tone audiometer on 2000 and 4000 cps over 25 dB All subjects, following the above 3 step examination, were tested on 8 frequencise with a Beltons Audiometer 15 C which was calibrated by Rudomose RA 106. A testing method used, was a 3 cross testing in 2 ascending and 1 descending trials. The audiological analysis shows the following: 1) The occurrence of noise-induced hearing loss is increased with increasing age and years of service. A closer relation was noted in the male than in female. 2) In both sexes there is a significant change in the direction of poorer hearing with increasing age especially for the higher frequencies. 3) There is a decrease in hearing sensitivity with increasing length of employment in both sexes,but it did not result in a direct proportionate greater loss with greater years of service. 4) Greater hearing losses occur I the left ears than in the right ears above 3000 cps. 5) Greater hearing losses occur in the male than infemale above 3000 cps. 6) The pure tone audiogram pattern reveals the dip form, divided dip form, and abrupt form in that order.restrictio

유도 결합 플라즈마 화학 기상 증착법을 이용한 저온 고속 TiO2 박막 증착 및 박막의 표면 거칠기 제어를 통한 초친수 특성 향상

Thesis(doctors) --서울대학교 대학원 :재료공학부,2008.8.Docto