• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.216-222
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• 2015

A previous velocity measurement system for marine sediment had several problems such as the errors occurred when picking first arrival time and the inconvenient measurement procedure. In order to resolve these problems, we developed a new acoustic properties measurement system by using PXI (PCI eXtentions for Instrumentation) module based on LabVIEW. To verify the new system, we measured the velocity and attenuation of sediment using the new system in a parallel with the previous system under the same experimental environment. The result of measurement showed 1~2% margin of error for the velocity as well as similar attenuation values. We concluded that the new system can efficiently measure the acoustic properties of marine sediment. It also has an advantage to construct the database of acoustic data and raw signal.

• Journal of the Korea Society of Computer and Information
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• v.12 no.3
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• pp.259-266
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• 2007

The parameters of electric acoustic characteristic used as standards to evaluate the performance of a small microphone are composed of sensitivity, harmonic distortion, frequency response, directivity and others. Such characteristic parameters should be designed differently depending on a purpose, so it is important to verify whether a small microphone was made appropriately for the purpose after measuring the acoustic characteristics. Therefore, a system that can measure the acoustic characteristic parameters of a small microphone using DSP, not only simultaneously but also in real-time, was implemented in this paper. To verify the implemented system, four kinds of microphones were measured and the results were compared with the data values of the acoustic characteristics of each microphone. There were a little discrepancy between them because the conditions when measuring the characteristics were not identical. But it was verified that the errors are within the error tolerance and it proved that the system can be used in place of the conventional equipment used in measuring the acoustic characteristics of small microphones.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.63-67
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• 1999

Recently, a method of measuring impulse response is widely used for a room acoustic evaluation instead of measuring reverberation time by white noise excitation. Comparing with the traditional reverberation time measurement, this method has many advantages such as good repeatability and the ability to extract various room acoustic parameters at one measurement. In this study, the author developed a measuring system that can extract mono-aural room acoustic parameters from an impulse response measured with MLS (Maximum Length Sequence) signal excitation. These room acoustic parameters include reverberation times(EDT, RT), speech intelligibilities(C50, C80, D, U50, U80, AI) and sound strength(G). This paper introduces the configuration of the developed measuring system, test results and discussions for the measurements at several rooms.

• The Journal of the Acoustical Society of Korea
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• v.29 no.6
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• pp.355-364
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• 2010

Considering biological safety, it is very important to measure acoustic power from ultrasonic array probe for diagnostic ultrasound imaging applications. In this paper, to measure acoustic power from each element on array probe for ultrasonic diagnostic equipment, we reconstruct and automate the acoustic power measurement system. The acoustic power from linear, phased and curved array were measured and analyzed. As a result of measurement, the effects caused by directivity of sound beam from curved array were founded. To remove these effects, we developed and applied the correction model. The proposed system is useful to evaluate characteristics of the acoustical output power of array probe.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.301-306
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• 2001

최근의 야외경기장의 설계는 운동 경기 뿐만 아니라 각종이벤트 및 대형콘서트를 수용하는 다목적경기장으로 건설되어지고 있으며 지붕의 $50\%$이상이 천장으로 덮히는 야외경기장의 건설이 증가하는 추세로 변화되고 있으며 이에 대한 음향장해 현상이 심각한 실정이나 이에 대한 건축음향적인 대책은 미미한 실정이다. 본 연구는 서울월드컵경기장을 중심으로 경기장의 음향시스템을 고찰하고 과 측정결과 치와 음향시뮬레이션 결과치를 음향인자 (잔향시간, 명료도, 음압레벨)들을 서울시의 설계기준과 비교분석 평가 고찰하는데 있다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.495-500
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• 2002

전주월드컵 경기장은 Fully Digital sidelobe-free array 방식의 음향시스템을 도입한 유일한 경기장으로서 대규모 경기장에 Line Array type의 스피커를 사용한 최초의 예가 된다. 현장음향실험을 통하여 경기장의 주요 음향 파라미터인 음압레벨(SPL), 잔향시간(RT), 음성명료도(D50), 음성이해도(RASTI) 등을 측정함으로 전주월드컵 경기장의 음향시스템의 특성과 종합적인 음향성능을 알아보고자 한다. 주음원(Messenger)만 사용하여 실험한 결과 음압레벨(SPL)은 관중석의 객석간 위치별 음압레벨 표준편차가 약 2.78dB로 나타났다. 이 값은 당초의 음압레벨분포편차의 목표치인 ${\pm}3dB$의 범위 이내로 나타났다. 또한 최대음압레벨은 평균 100.1dB로 목표치인 96dB을 초과하는 것으로 나타났다. 잔향시간(RT)은 공석시 전체 관중석 평균 2.94초로 나타났으며, 1000Hz에서의 평균 잔향시간은 2.58초로 나타났다. 잔향시간은 실제 경기장의 사용 시 약 0.3-0.4초의 감소가 발생되리라 판단된다. 음성명료도(D50)는 전체 관중석 평균 $56.2\%$로 매우 양호한 상태로 나타났고 음성이해도(RASTI)는 전체 관중석 평균 0.63으로 목표치인 0.5를 상회하는 것으로 나타났다. 이상의 현장음향실험 결과를 분석한 결과 전주월드컵 경기장의 음향성공은 음향설계 요건을 만족하는 것으로 나타났고 야외 경기장 같은 대형공간에서의 음향시스템에 있어서 Fully Digital sidelobe-free array 방식의 음향시스템의 적용가능성을 보여주고 있는 것으로 나타났다.

• Journal of Internet Computing and Services
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• v.18 no.1
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• pp.57-64
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• 2017

Recent automobile manufacturing technology has improved not only the function and performance of cars, but also the audio systems in cars so as to increase their marketability. Automobile manufacturers always have the option of simply installing an expensive acoustic system to help customers enjoy a high-level sound quality car audio system. However, this also tends to increase the MSRP (Manufacturer's Suggested Retail Price) of the car. Therefore, it is desirable, where possible, to enhance the sound quality of plainer, less expensive audio devices to help customers feel as if they have a high-quality and expensive audio device in their car. In order to make this happen, the manufacturer must develop an optimal interior environment and audio system at a relatively lower cost. To this end, features of the car audio system can be enhanced by analyzing audio frequency response and using performance metrics to figure out the characteristics of the human auditory system. This study analyzed the sound field of Korean Recreation Vehicles (RVs) using the Internet of Things (IoT) sensor for the measurement of car audio system. As a result, high energy of sensitive bandwidth, one of the human auditory characteristics often makes annoying sound. This study also found that increasing the frequency response flatness is required by taking human auditory field into account when designing the car audio system for the future.

• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.509-517
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• 2013

In this paper, we researched a method that makes a good acoustic-speech system using a digital signal processing technique with dynamic microphone as a transducer. Good acoustic-speech system should deliver the original sound input to electric signal without distortion. By measuring the frequency response of the microphone, adjustment factors are obtained by comparing measured data and standard frequency response of microphone for each frequency band. The final sound levels are obtained using the developed adjustment factors of frequency responses from the microphone and speaker to match the original sound levels using the digital signal processing technique. Then, we minimize the changes in the frequency response and level due to the variation of the distance from source to microphone, where the frequency responses were measured according to the distance changes.

• The Journal of the Acoustical Society of Korea
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• v.14 no.6
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• pp.40-47
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• 1995

A system for measurement of ultrasonic velocity, attenuation and complex modulus of materials by using the spectral analysis method of pulses has been constructed and its performances are estimated. The system has a mechanical scanning part of an acoustic microscope with a ZnO plane wave transducer of the resonant frequency of 85MHz. Ultrasonic velocity has been obtained by the intervals of maxima (or minima) on the power spectrum of a pulse train reflected from the surface and bottom of a specimen, and attenuation has been obtained by the power spectra of three pulses reflected from the surface and the bottom of a specimen and the surface of a standard specimen. The measured results for materials such as fused quartz, polyester show that the system has very high accuracy.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.713-722
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• 2022

In this paper, the flow performance and aero-acoustic noise generated by the target centrifugal fan system were investigated numerically and experimentally. Also, the numerical method for Computational Aero-Acoustics were evaluated by comparing each method. To analyze the performance of the centrifugal fan experimentally, the acoustic power level was measured in the semi-anechoic chamber using microphones, and the active frequency range for the noise performance was identified and that frequency range was applied for Computational Aero-Acoustics (CAA) techniques as sampling frequency. Then, Navier-Stokes equation and the Ffowcs Williams&Hawking equations were used to analyze the flow and sound power numerically, respectively, and a virtual acoustic radiation plane was designed and used for the implementation of the sound field. The accuracy and numerical characteristics of the numerical methods were validated by comparing simulated acoustic power levels with acoustic power levels measured.