• Title/Summary/Keyword: 음압감도레벨

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APMP (Asia Pacific Metrology Programme) Regional Intercomparison Results of Acoustic Calibrators (음향교정기의 아시아.태평양 지역 국제비교 결과)

  • 서상준;서재갑;조문재
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.6
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    • pp.463-471
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    • 2003
  • The results of the APMP (Asia Pacific Metrology Programme) regional intercomparison of acoustic calibrators were reviewed and analyzed. The artefacts used in intercomparison are a sound level calibrator and a pistonphone. The microphones used to measure the output pressure level are 1" and 1/2" standard microphones (LS1P, LS2P) as well as 1" and 1/2" reference microphones (WS1P/F, WS2P/F). The results obtained using standard microphones are satisfactory, but those obtained by the reference microphones, even though E/sub n/ values are within ±1.0, showed great deviations. Such results had come from the inaccurate calibration of reference microphones. By using the correct calibration results which were obtained by the recently established international standards, the new results were very similar to those of the foreign standard institutes.

A Fundamental Study on the Auditory Characteristics of Amberjack Seriola dumerili in the Coast of Jeju Island (제주 연안산 잿방어의 청각특성에 관한 기초적 연구)

  • 서익조;김성호;김병엽;이창헌;서두옥
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.39 no.4
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    • pp.269-275
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    • 2003
  • In this paper, We examined auditory threshold and critical ratio of amberjack seriola dumerili, in the Jeju Island coastal waters, to find out hearing ability of the fish. The auditory threshold level, critical ratio and hearing index of amberjack were determinded by conditioning method using a sound coupled with electric shock in the condition of ambient noise or white noise in an experimental water tank. The audio-signals of pure tone and electric shock were from 80 HZ to 800 Hz and DC 7 V, respectively. Values for the critical ratios were calculated in terms of the masked thresholds using the noise projected to stable spectrum levels at all measurement frequencies of background noise. Masking noises were in the spectrum level range of 65 dB∼75 dB $(re 1{\mu}Pa\sqrt{Hz})$. The auditory thresholds of amberjack within the test the frequencies were most sensitive at 300HZ as 94.5 dB. The critical ratios of fishes ranged from 36.4 to 52.8 dB. The noise spectrum level that started masking was about 58∼72 dB within frequencies.

Uncertainties in Pressure Calibration of Laboratory Standard Microphones by Reciprocity Technique (가역방법에 의한 표준 마이크로폰 음압교정의 불확도)

  • 서상준;권휴상;이용봉;서재갑
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.2
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    • pp.90-102
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    • 2004
  • According to the Mutual Recognition Arrangement (MRA), the calibration and/or test laboratories should satisfy the management and technical requirements ISO 17025 or equivalent. Chapter 5, Section 5.10.4 of the technical requirement of ISO 17025 suggests the required informations for calibration certificates, one of them is to state the uncertainty of measurement. The uncertainties of measurement in reciprocity calibration of standard laboratory microphone were calculated. The expanded uncertainties for 1 and 1/2 inch microphones were 0.03 dB in the middle frequency range and they increased up to 0.10 dB and 0.11 dB at 20 Hz, 0.07 dB and 0.08 dB at high frequency, respectively.

Investigation of the Noise Reduction in the Hollow Cylinder Structure (중공 원통형 구조물의 전달소음 감소 방안 연구)

  • Lee, Sang-Won;Lee, Jong-Kil;Jo, Chi-Yong
    • 대한공업교육학회지
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    • v.36 no.1
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    • pp.115-130
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    • 2011
  • When the hollow cylinder structure moves in underwater with high speed structural can be propagated from the end of the structure to the front side. This noise can reduce the sensitivity of the conformal array which installed in the surface of the cylinder. To reduce this noise propagation it is suggested to install two self-reduction rings at the surrounding of the cylinder which is 500mm in diameter and 840mm in length. The places of the two noise reduction rings are 120mm and 240mm point from the end of the structure. Two noise reduction rings reduced 10.1 % of maximum stress. When outside noise frequency applied to the structure from the 4kZ to 6kHz, 20dB noise reduction was calculated using 6 order polynomial equation. When outside noise frequency also applied to the structure with 200Hz, 500Hz, 900Hz, maximum sound pressure level point moved to the end of the structure. Most conformal sensors are fabricated at the front side of the structure. Based on the simulation results proposed two rings can be reduced noise propagation from the tail of the structure effectively.