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ID 16230
Eprint ID
16230
フルテキストURL
Thumnail 97_963.pdf 2.38 MB
タイトル(別表記)
Experimental study on vibration analysis of the Infant skull by Holographic interferometry
著者
武田 恒雄 岡山大学医学部耳鼻咽喉科学教室
抄録
Vibratory mode of the infant skull was observed and analysed by holography to elucidate the mechanism of bone-conduction hearing in the childhood. Three dried human infant skulls, one of six months, two of eight months postnatal age, were used. As the cranial suture was incomplete with the wide fonticulus remaining and the composition was not so dense or strong as that of the adult, very careful manipulation was needed in the experiment with the infant skull. Consequently, an acoustic loud-speaker was utilized to make the infant skull vibrate in the free sound field, instead of using direct vibrator conventionally attached to the adult skull for the measurement of vibration. An area around the foramen occipitale magnum was fixed by means of bolts, and the skull was stood on a table. Attempts were made to change the frequency and intensity of the test sounds during the experiment. The sound pressure level of the sound field was measured with a noise meter. The value measured at the site of the skull closest to the loud-speaker was regarded as the intensity of the test sound. The resulting pattern of vibration was recorded and reconstructed by holographic interferometry. As the light source for holography helium-neon laser was used. Interference fringes were observed at 110 phon or more of the intensities of the test sounds. When frequency of the test tone was low such that 500 Hz or less, interference fringes of parallel lines were observed in the hologram. This meant the skull was found to vibrate as a whole, and the sound signal seemed to be transmitted by "inertia bone-conduction" in the mechanism of hearing when the frequency of the test sound was 500 Hz or less. on the other hand, at 1 kHz and more of the test frequency, the vibratory pattern changed into concentric fringes with multiple maximum points of amplitude. Then, it was clarified that when the frequency was 1 KHz or more, "compression bone-conduction" was added up in the hearing mechanism. At about 3 KHz of test sound, the vibratory amplitude was larger than any other frequencies used, suggesting that 3 KHz was the closest to the resonance frequency of the infant skull.
キーワード
vibration analysis
infant skull
holography
bone-conduction hearing
発行日
1985-12-30
出版物タイトル
岡山医学会雑誌
出版物タイトル(別表記)
Journal of Okayama Medical Association
97巻
11-12号
出版者
岡山医学会
出版者(別表記)
Okayama Medical Association
開始ページ
963
終了ページ
972
ISSN
0030-1558
NCID
AN00032489
資料タイプ
学術雑誌論文
オフィシャル URL
https://www.jstage.jst.go.jp/article/joma1947/97/11-12/97_11-12_963/_article/-char/ja/
関連URL
http://www.okayama-u.ac.jp/user/oma/index.html
言語
Japanese
OAI-PMH Set
岡山大学
著作権者
岡山医学会
論文のバージョン
publisher
査読
有り
Sort Key
4
Eprints Journal Name
joma