• 센서학회지
• /
• 제22권6호
• /
• pp.410-414
• /
• 2013

As one of the effective methods for researching the objective tinnitus detection, the GPIAS (Gap Pre-pulse Inhibition of Acoustic Startle) measurement has been used to verify the existence of animal tinnitus objectively. The level and pattern of the background sound presented prior to a startle pulse are closely related with the GPIAS results. But the effect of the starting point of the background sound on animal startle responses has not been reported yet. In this paper, we present the implementation of a GPIAS measurement system based on an unconstrained enclosure to avoid animals' excessive constraint stress and deal with the animals' growth. After the performance of our implemented system has been tested through the animal experiment using 4 SD-rats, the effect of starting point of stimulus background sound on the startle response has been studied by the use of our implemented system. Through the results, it is verified that our system can measure the inhibition of animal startle responses due the gap pre-pulse for GPIAS calculation and the background sound starting point does not significantly effect on the startle response and the GPIAS values if the background sound continues for more than 300msec before a gap pre-pulse is presented.

• 한국유체기계학회 논문집
• /
• 제7권3호
• /
• pp.7-13
• /
• 2004

In this paper, we identify the noise source and the path of a chiller. This chiller is newly developed for R-l34a refrigerant and 250 RT cooling capacity. The measured overall SPL of the developed turbo-chiller is about 100 dBA. Due to the high rotating speed of the centrifugal impeller, the nun noise source of the chiller is the blade passing frequency and its higher harmonics of the centrifugal impeller. This generated soundpropagates through the duct, and then transmits and radiates to the outer field. From the experiment, it is found that the high frequency noise is mostlytransmitted and radiated through the elbow duct, but the low frequency noise is transmitted and vadiated through the condenser wall. Therefore applying the absorbing material is an effective way of reducing the high and low frequency noise simultaneously. Measurement results show that the application of the sound absorbing material to the elbow duct reduced the overall sound pressure level by 4 dB compared to the 9 dBA reduction for the case of full enclosure. In order to control the generated noise, a dissipativetype silencer is also designed and tested. The silencer reduced the radiated noise about 7.5 dBA.

• 한국소음진동공학회논문집
• /
• 제24권7호
• /
• pp.525-536
• /
• 2014

In this paper, GUI program for microspeaker system simulation program was developed and verified through closed box, vent box and 6th order bandpass enclosure system. By using the pseudo loudspeaker model concept, TS parameters and rear volume of microspeaker were identified. Their suitabilities were proved by comparing test results with simulations of electrical impedance and sound pressure response curves for the three box types; closed box, vent box and 6th order bandpass box. Also, MSSP was found to be effective regardless of the microspeaker's shape, either circular or rectangular shape. MSSP can be used for the microspeaker system simulation, and can give a general prediction of such as; sound pressure level curve, electrical impedance, diaphragm velocity and displacement curve according to multiple design parameters; diaphragm mass, compliance, force factor, front and rear volume, front and rear port's diameter and length.

• The Journal of the Acoustical Society of Korea
• /
• 제24권3E호
• /
• pp.90-98
• /
• 2005

Enhanced approach using computational and experimental method is proposed and performed to describe very well the behavior of loudspeaker than conventional method. Proposed procedure is composed of four parts. First, Thiele-Small parameters for test loudspeaker are identified by an electrical impedance method like as a delta mass method. Second part includes the processes to measure physical properties. Physical data like masses and thicknesses of loudspeaker's components are measured by an electrical precision scale and a digital vernier caliper. Third, the identified Thiele-Small parameters are proposed to be used as load boundary conditions for vibration analysis instead of electromagnetic circuit analysis to get a driving force upon bobbin part. Also, these parameters and physical data are used to modify physical properties required for computation to accommodate simulated sound pressure level with measured one for loudspeaker enclosure system. These data like as Young's modulus and thickness for a diaphragm are required for vibration analysis of loudspeaker but not measured accurately. Finally, it was investigated that simulated sound pressure level with full acoustic modeling including an acoustic port for test loudspeaker agreed with experimental result very well in the midrange frequency band(from 100 Hz to 2,000 Hz). In addition, several design parametric study is performed to grasp acoustical behaviors of loudspeaker system due to variations of diaphragm thicknesses and shapes of dust cap.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
• /
• pp.785-790
• /
• 1994

The active noise control which regards the acoustic power as a target function to be minimized, is analyzed to test its feasibility of which simplifies the measurement system compared with the global acoustic energy based active noise control system. In fact, it is found that the acoustic power based active noise control strategy is equally likely as good as the global acoustic energy based active noise control method if the acoustic field of interest is diffusive or very low model density one. In the intermediate model density field, we also demonstrate that the power based control gives the similar results as the energy based control in terms of global sound energy reduction for the lightly damped enclosure which might be most important system in practical application. From all the theoretical and power based control strategy is dependent on the characteristics of the acoustic field to be controlled; i.e., the model density distribution, the degree of reverberation, and on the strength of modal interaction of the control source with the primary source; i.e., the location of control source.

• 한국화재소방학회논문지
• /
• 제32권6호
• /
• pp.34-39
• /
• 2018

본 논문에서는 최초로 음파 소화기를 이용한 자동 화재진압 기능을 가진 안전 스토브 아키텍처를 제안하고 개발하였다. 화재가 발생하면 화재 센서와 연동된 마이크로컨트롤러가 화재를 감지하고 음파 소화기를 구동하여 화재를 진압하는 구조를 가진다. 음파 소화기는 스피커와 콜리메이터로 구성되며, 오디오 증폭기를 포함하는 구동모듈에 의해 구동된다. 스토브를 둘러싸는 인클로저를 사용해 거리에 따른 음파의 확산을 막아 음파의 감쇠를 줄일 수 있었다. 이때, 사용된 음파의 주파수는 50 Hz이며, 음압은 소화기로 부터 0.5 m 거리에서 93 dBA로 측정되었다. 7 cc 및 14 cc의 가연성 액체에서 발생한 화염에 대해 진화에 소요되는 시간은 각각 최대 8 s와 15 s로, 각각 자연소화 시간의 24%와 42%에 해당한다. 제안된 안전 스토브는 기존 안전 스토브와 비교하여 무해하고 잔여물질이 남지 않기 때문에, 다양한 가전기기에 적용되어 원활한 초기 화재 진압 및 화재 확산 방지에 기여할 것으로 기대된다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1991년도 춘계학술대회논문집; 한국해사기술연구소, 대전; 1 Jun. 1991
• /
• pp.65-69
• /
• 1991

소음제어대책 수립시, 흡음구조는 공조용소음기, 공업용소음기, Enclosure, 실 내 흡음판등에 폭넓게 이용되고 있다. 흡음구조의 재료중 글라스울은 뛰어난 흡음성능과 고온에서의 내구성 및 난연성등으로 인하여 여러 흡음재료중에 서 가장 많이 이용되고 있으나 글라스율 미립자의 비산 및 강도문제로 글라 스율에 글라스 클로스(Glass Cloth), P.E.Film등과 같은 글라스울 비산방지막 과 유공함석판을 붙인 흡음구조체로 제작하여 이용하는 것이 일반적이다. 국 내외적으로 글라스울만의 흡음율 데이타는 각종 문헌등에 많이 발표되어 있 으나 글라스울에 글라스울 비산방지막과 유공함석판을 붙인 흡음구조체의 흡음율데이타는 거의 없는 실정이다. 본 연구에서는 이러한 글라스울 흡음구 조체의 글라스울의 밀도, 글라스울 비산방지막의 종류, 유공함석판의 유공치 수 등에 따른 흡음특성을 잔향실법 흡음율측정방법에 의해 측정 평가하고 이들을 상호 비교검토하여 각종 소음 제어대책의 기초 설계자료로 제시하고 자 한다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.166-169
• /
• 2004

In this paper, computational analysis and experiments of subwoofer for car audio speaker system were performed and discussed to analyze acoustical phenomena for subwoofer. Ported enclosure system with subwoofer were manufactured and provided for test and simulation purposes. Subwoofer with single voice coil and double voice coil were identified by linear and nonlinear parameter identification method for loudspeaker parameters. For high power inputs to subwoofer, sound pressure levels were compared according to input powers with linear and nonlinear loudspeaker models. For subwoofer system with high power nonlinear speaker model was showed to be adequate to describe the behaviour of loudspeaker.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 추계학술대회논문집
• /
• pp.403-408
• /
• 2000

An acoustic field in a 3 dimensional enclosure is caused from interference between sound sources and the complex reflections from wall. Therefore, changing an acoustic property of wall such as admittance means generating another acoustic field. The purpose of this paper is utilizing the characteristic to make a quiet zone. First, this paper shows that the control material is essentially on the same road as active noise control(ANC). That is, we can consider the control material as the control source of ANC. However we cannot control the reflection strength of it. Second, through a numerical simulation, this paper shows that the position of the control material is an important variable of the control.

• 한국안전학회지
• /
• 제11권4호
• /
• pp.135-142
• /
• 1996

Prolonged in-plant personnel exposure to high noise levels results in permant hearing damage. There are no way to correct this hearing damage by treatment or use of hearing aids. Therefore, every employer is responsible for providing a workplace free of such hazards as excessive noise. This study was carried out to evalute and predict a given noise environment based on specific limit as the noise guarantee for a newly-founded petrochemical plant. The maximum total sound level should not exceed 85dBA in the work area, except where the area is defined as a restricted area and 70dBA at the plant boundary. Prediction of the noise levels within the plant area for a newly-founded petrochemical plant was achieved by dividing all plant area into 20m$\times$20m regular grid spaces and noise level inside the area or unit that in-plant personel exposure to high noise levels was estimated computed into 5m$\times$5m regular grid spaces. The noise level at the grid point that was propagated from each of the noise sources(equipments) computed using the methematical formula was defined as follows : $SPL_2$=$SPL_1-20log{\frac{r_2}{r_1}}$(dB) where $SPL_1$ =sound pressure level at distance $r_1$ from the source $SPL_2$=sound pressure level at distance $r_2$ from the source As a result, the equipments exceeded noise limit or irritaring noise levels were identified on the specific grid coordinates. As for equipments in the area that show high noise levels, appropriate counter-measures for noise control (by barriers, enclosure, silencers, or the change of equipments, for example) should be reviewed. Methods for identifying sources of noise applied in this study should be the model for prediction of the noise levels for any newly-founded plant.