• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.6993-6997
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• 2014

The aim of this study was to experimentally investigate the sound quality characteristics, such as sound deflection, sound pressure level and frequency characteristics of a magnetic type speaker in an anechoic chamber to overcome the sound quality and voice-coil temperature problems. To accomplish this, the sound quality performance of the magnetic type speaker was tested according to the magnetic fluid amount and magnetic field intensity. The sound deflection, sound pressure level, and frequency characteristics were measured using the Smarrt program. As a result, at a magnetic fluid amount of 2.4 ml, the sound deflection and the sound pressure level of the magnetic type speaker were enhanced by comparing with those of the general type speaker. The frequency characteristics and the sound pressure level of the magnetic type speaker were enhanced greatly with increasing magnetic field intensity from 8.06 mT to 9.10 mT. In addition, the sound deflection of the magnetic type speaker was 0.01% lower than that of the general type speaker.

• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.133-150
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• 1997

The purpose of this paper is to develop an algorithm of classification and interpretation of seafloor based on side scan sonar data. The algorithm consists of mosaicking of sonar data using navigation data, correction and compensation of the acouctic amplitude data considering the charateristics of the side scan sonar system, and segmentation of the seafloor using digital image processing techniques. The correction and compensation process is essential because there is usually difference in acoustic amplitudes from the same distance of the port-side and the starboard-side and the amplitudes become attenuated as the distance is increasing. In this paper, proposed is an algorithm of compensating the side scan sonar data, and its result is compared with the mosaicking result without any compensation. The algorithm considers the amplitude characteristics according to the tow-fish's depth as well as the attenuation trend of the side scan sonar along the beam positions. This paper also proposes an image segmentation algorithm based on the texture, where the criterion is the maximum occurence related with gray level. The preliminary experiment has been carried out with the side scan sonar data and its result is demonstrated.

• Explosives and Blasting
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• v.18 no.3
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• pp.77-82
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• 2000

현재까지 폭풍압은 음압과 음압레벨로 측정되어 왔다. 그러나 발파 소음에 의한 인체의 반응이나 가축의 피해 산정 등의 문제에서는 현행 소음진동규제법에서 명시하는 바, 인체의 청감보정이 이루어진 소음레벨을 사용하므로 변환문제가 발생한다. 본 연구에서는 발파 진동 계측기기로 계측한 데이터를 디지털 필터로 처리하여, 소음레벨로 변환하는 프로그램을 개발하고, 이를 실제 발파계측결과에 적용하였다. 그 결과, 국내에서 널리 사용되고 있는 Instantel Inc,의 Blast1ate series에서 계측된 소음데이터가 정밀도 높은 소음레벨로 변환이 가능하였다. 비슷한 정밀도로 계측결과를 ASCII file로 송출할 수 있는 기종에서 계측된 자료도 같은 정도로 처리할 수 있을 것으로 판정되었다.

• Fire Science and Engineering
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• v.34 no.4
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• pp.29-35
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• 2020

This study was conducted to examine the performance in the space for a single alarm type detector installed in a single house. Three types of houses were used, including two types of one-story and two-story houses. A computer simulation program was used to predict the sound pressure level in response to the occurrence of an alarm sound in a residential space. The characteristics of the sound source applied to the simulation were directly measured and used as input data. As a result of simulation, it was found that the sound pressure level in the kitchen and living room generally met the standard when the alarm sound of the detector occurred. However, the sound pressure level in the bedroom was predicted to be at least 20 dB (A) lower than the American Fire Protection Association standard of 75 dB (A). Therefore, a plan should be prepared to maintain a sufficient sound level in the bedroom space inside the house, and efforts will be needed to ensure safe evacuation in case of fire by establishing relevant standards.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.69-79
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• 2017

The purpose of this study is to reconsider the rating method for the floor impact sound insulation performance in current criterion. Although there are some arguments about proper standard heavy impact source with reproducibility of actual impact source in residence building, bang machine is adopted as the only standard heavy impact source in domestic criterion. To inspect the rating methods of evaluation criteria, this study conducted vibration test for both of standard heavy impact sources and actual impact sources. Using the test results, the floor impact sound insulation performance levels were assessed by each of several criteria. In addition, low frequency noise beyond current criteria was evaluated. Consequently, the floor impact sound levels have different performance levels according to adopted criteria, and measured floor impact sounds are bound to annoy the neighbors in the low frequency range. Current criteria does not consider the spectrum characteristics of floor impact sound according to impact sources and low frequency noise. This may cause the difference between the floor impact sound insulation performance level and human perception. Thus current criterion needs to be complemented to reflect the spectrum characteristics of floor impact sound levels according to impact sources and sound pressure levels in low frequency range.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.510-510
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• 2010

우리나라에서 고속철도는 이미 중요한 대중교통수단 중 하나가 되었으며 향후에도 운행구간을 확대할 예정인 만큼 승객수도 더욱 증가할 것으로 보인다. 또한 승객수가 증가하는 만큼 정숙한 실내환경의 조성 또한 요구되고 있다. 하지만 현재 철도차량 소음에 관한 연구는 대부분 철도 외부에서 방사되는 소음에 한정되어 있으며 철도차량의 내부 소음 특성에 대한 연구는 미비한 상황이다. 현재 국내 환경소음에 대한 규정은 음압레벨만을 기준으로 하고 있지만 실제로 사람이 소음에 대하여 느끼는 청감특성을 나타내기에는 음압레벨만으로는 부족하다. 사람의 청감특성을 효과적으로 반영하기 위하여 음질(Sound Quality)평가의 방법에 대해 현재 활발하게 연구되고 있다. 본 연구에서는 국내에서 운행중인 고속철도 실내 소음의 특성에 대하여 연구하였다. 음압레벨과 loudness의 관계에 대하여 분석하였고 Zwicker parameter과 ACF, IACF 분석을 통하여 객관적인 음질평가를 실시하였다. 또한 청감실험을 통하여 주관적인 음질평가를 수행하여 청감특성에 대하여 분석하고 객관적 평가의 결과를 검증하였다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.2
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• pp.151-155
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• 2001

In order to obtain the fundamental data on the auditory thresholds of fishes for marine ranching, the auditory thresholds of black rockfish Sebastes inermis were measured in the presence of masking noise in the spectrum level range of $73\~83$ dB (0 dB re $1{\mu}Pa/\sqrt{Hz}$) with a classical cardiac conditioning technique. Critical ratios were about $28\~34$ dB at $80\~300$ Hz and $47\~52$ dB at $500\~800$ Hz. The ratio increased almost linearly with increasing frequency to 500 Hz. The noise spectrum level at the start of masking was about 70 dB within the frequency range of $80\~800$ Hz excepting 65 dB at 300 Hz. It means that hearing of the black rockfish is masked in the natural environment with the noise spectrum level above 65 dB. The sound pressure level of $200\~300$ Hz recognized by black rockfish was above 96 dB under the ambient noise and the critical ratio of them was above 26 dB.

• Journal of Fisheries and Marine Sciences Education
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• v.12 no.1
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• pp.1-10
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• 2000

In order to obtain the fundamental data on the auditory thresholds of fishes for marine ranching, the auditory thresholds of black rock fish Sebastes Schlegeli were measured in the presence of masking noise in the spectrum level range of 73 - 83dB (0dB re $1{\mu}Pa/{\sqrt{Hz}}$) with a classical cardiac conditioning technique. Critical ratios were about 19 - 30dB at 80 - 300Hz and 46 - 54dB at 500 - 800Hz. The ratio increased almost linearly with increasing frequency to 500Hz. The noise spectrum level at the start of masking was about 70dB within the frequency range of 80 - 800Hz excepting 65dB at 300Hz. This suggests that hearing of the black rock fish is masked in the natural environment with the noise spectrum level above 65dB. The sound pressure level of which the signal sound of 100 - 200Hz is recognized by black rock fish under the ambient noise is above 90dB and the critical ratio of them is above 20dB.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.421-426
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• 1998

국악전용 공연장으로 지어진 국립국악 소극장의 음향 특성을 실내 음선도, 암소음, 잔향시간 및 음압분포에 의해 분석.평가하였다. 연구결과 무대 앞부분과 객석모서리에서 음선경로차가 17m 이상으로 나타나 회주공조현상의 발생이 예측되며 남부순환도로와 인접하여 소극장내에 높은 암소음이 측정되었다. 잔향시간의 측정결과 과다한 실내 흡음력으로 인해 공석시에 계획값 보다 0.8초 정도가 짧으며 이는 관객입장시 더욱 악화될 것이 예측되어 1석당 실용적을 증가와 실내 흡음력을 가능한 줄일 필요가 있다. 음압레벨은 음악당 전 객석에서 고른 음압분포가 보이고 있으나 무대 음원에서 객석전열 사이에 초기 음압감쇠가 크게 나타나 무대주변의 음압 보강이 요구된다.

• The Journal of the Acoustical Society of Korea
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• v.32 no.4
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• pp.287-293
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• 2013

We present a parametric array signal generating system using $3{\times}16$ transducer array which is composed of multi-resonant frequency transducers of 20kHz and 32.5kHz. To drive transducer array, sixteen channel amplifier using LM1875 chips is designed and implemented, and the PXI system based on the LabView 8.6 for arbitrary signal generation and analysis is used. Using the proposed system, we measure sound pressure level and beam pattern of difference frequency and verify the nonlinear effect of difference frequency. The theoretical absorption range and the Rayleigh distance are 15.51m and 1.933m, respectively and we verify that sound pressure of difference frequency is accumulated and increased at the near-field shorter than the Rayleigh distance. We verify that the beam pattern of the measured difference frequency and the beam pattern obtained by the superposition of two primary frequencies are similar, and high directional parametric signal was generated.