• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1146-1151
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• 2011

Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.196-201
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• 2011

Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

• 소음진동
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• 제9권1호
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• pp.141-148
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• 1999

Resilient mounting is effective measures to reduce the structure-borne noise and radiated noise for many applications. The acoustic stiffness (frequency-dependent stiffness) of resilient mounts is an important parameter required in order to model vibration isolation with high accuracy. It is general to use measurement method for obtaining acoustic stiffness of complex resilient mounts under static preload. In this paper, the principles of measuring acoustic stiffness were described and the developed test apparatus was introduced. Also, the feasibility of the test apparatus is illustrated by measurement results of a resilient mount.

• 비파괴검사학회지
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• 제23권3호
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• pp.280-284
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• 2003

사용하지 않은 새 금속 압력용기에 대하여, 사용 전 음향방출시험을 수행할 때 장비점검, 탐촉자간 거리, 탐촉자 위치, 전 측정 시스템 점검, 가압방법, 잡음 제거법 및 시험 결과의 평가 등에 대한 절차를 수립하고 현장 응용시험이 수행되었다. 일반적으로 음향방출 시험은 많은 잡음을 포함하는데 시험동안 관찰결과를 기록하여 평가 시 시간 필터링함으로서 잡음을 제거할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.207-210
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• 2014

This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. Intense acoustic load is generated when a launch vehicle is lifted off, and it can induce vibrations of a launch vehicle which cause damage or malfunction of a launch vehicle and a satellite. Lift-off acoustic loads of NARO are predicted by the modified Eldred's second method and the result is compared with the measured data in flight test. The prediction shows similar peak and shape of spectrum to the test data, but some discrepancy can be observed due to the predicted margin. In order to reduce such discrepancy, the sound pressure levels with four source distribution assumptions are calculated. Also, the surface diffraction effects are considered in the predict ion of lift-off acoustic loads, and the predicted result is more similar to the test data.

• 항공우주기술
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• 제10권1호
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• pp.13-19
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• 2011

수정된 NASA SP-8072 분포 음원 방법 (Method 2)를 이용하여 KSLV-I의 발사 음향 하중을 예측하고, 이 결과를 비행 시험시의 측정 결과와 비교하였다. 2차 비행 시험시에 케이블 마스트의 4개소에서 발사 음향 하중을 측정하였고, 인터스테이지의 텔레메트리 데이터도 입수하여 비교하였다. 예측된 음향 하중 스펙트럼은 측정 스펙트럼과 유사한 피크 주파수 및 형태를 가지며 약 7dB의 안전 여유를 가지고 예측됨을 알 수 있었다.

• 대한의생명과학회지
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• 제22권4호
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• pp.115-126
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• 2016

Audiometric calibration is a prerequisite for securing the reliability of audiometric test results by checking the internal consistency of the relevant instrument. The purpose of this review is to help instrument operators understand the calibration procedure of aural acoustic immittance instrument which is frequently used for objective assessment. By referring to the latest international standards and the national standards relevant to the aural acoustic immittance instrument, the following parameters will be reviewed: 1) introduction of performance characteristics, 2) detailed procedure of the calibration method. According to the newest international and national standards [IEC 60645-5 (2004), ANSI S3.39-1987 (R2012)], the aural acoustic immittance instrument basically includes six components: 1) calibration cavity, 2) acoustic immittance analysis system, 3) probe assembly/unit and signal, 4) pneumatic air-pressure pump system, 5) acoustic reflex activator system and 6) tympanogram and acoustic reflex plotting system, each of these components should meet set standards. The result of behavioral hearing tests is influenced by various complex factors including the examinee's cooperation, background noise of the examination room, measurement method, skill level of the audiologist and calibration status, but the objective hearing tests is more influenced by the calibration status of the instrument than any other factors. The audiologist should take full responsibility for the reliability of the hearing test result, so he/she should carry out the calibration check and adjustments of aural acoustic immittance instrument periodically and maintain the instrument continuously by referring to the newest standards and the manufacturer's instruction manual.

• 한국소음진동공학회논문집
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• 제25권6호
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• pp.440-446
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• 2015

Acoustic signal is emitted from a vessel and received by a cylindrical array sensor at some distance from the vessel. Acoustic signal is the source for a cylindrical array sensor which is designed to detect the acoustic signal. Cylindrical array sensors seldom have an ideal hydrodynamic shape and are not sufficiently robust to survive without some protection and they are normally housed in a sonar dome. Reflected signals by some structure inside a sonar dome make unwanted signals. Therefore, an acoustic baffle is used to minimize unwanted signals. The performance of the acoustic baffles can be determined from the acoustic numerical analysis at the design stage. In this study, finite element method was used to analyze the acoustic field around the cylindrical array sensor and baffle effects. The baffle performance can be defined the echo reduction. To show the baffle performance, the specimens were made for pulse tube test and echo reductions were measured during the test. In this paper, the effect of echo reduction of the acoustic baffle was discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.448-452
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• 2002

We report the number of calibration and test for acoustic field which were conducted in KRISS between the year of 1990 and 2001. The items contain sound level meter and calibrator for calibration and sound absorption coefficient, transmission loss, sound pressure level of siren, sound pressure level and power of acoustic instrument and relative accessories for test. The data show that the number of them have been increased continuously.

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1108-1114
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• 2006

Underwater acoustic transducers can be exposed to a underwater explosive shock caused by various types of underwater weapon. So, a robust anti-shock design is required for transducers to endure the underwater explosive shock. To check the anti-shock characteristics of a transducer, underwater explosive shock test is needed. The conditions of underwater explosive shock test are set up referring to various oversea explosive shock test specifications, and the explosive shock pressure values are calculated according to those conditions. Transient analyses art: carried out for two kinds of underwater acoustic transducer model to verify the anti-shock characteristics. The applied model has robust anti-shock characteristics enough to endure the explosive shock up to 2300 psi. In the future, the transducer design should be certified through the fields test, and modified if needed.