• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.344-350
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• 2024

A Reference Sound Source (RSS) is an important standard device employed in measuring sound power. The specifications of RSS is specified in international standards, and it is classified as a major calibration item in the field of acoustic metrology. Since the output power of RSS is affected by the supply voltage, each country needs to secure its own calibration service system. In this study, a procedure for calibrating a RSS is established based on the reverberant room conditions and uncertainty evaluation is conducted. Basically, the calibration procedure can apply a precision measurement process of acoustic power, and here, the measurement method using the reverberation chamber of ISO 3741 is applied. For this purpose, a measurement system is constructed, measurements are conducted with two types of RSS, and measurement uncertainty is evaluated. Through measurement examples, it is confirmed that the non-uniformity of the sound pressure distribution in the reverberation room and the volume measurement uncertainty contributed significantly to the overall uncertainty. Additionally, the influence of input voltage is experimentally examined to examine the uncertainty contribution that can be reflected in acoustic power measurements.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.53-56
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• 2006

최근 가정용 로봇 연구가 활발히 진행됨에 따라, 가정과 같은 다이내믹한 환경에서 로봇이 목소리를 포함한 음원에 반응하고 그 위치를 정확히 찾아가는 것이 매우 중요해지고 있다. 인간이 목표물에 도달하기 위해 경로를 선택할 때, 그 목표물이 소리인 경우는 현재 위치에서 음원의 방향을 추적한다. 또한 그 목표물의 위치가 지도로 주워질 경우에는 현재 위치와 목표불의 절대적 방위를 기준으로 추적한다. 본 논문에서는 이처럼 사람이 다른 사람의 목소리를 듣고 반응하거나 어떤 방향으로 가고자할 때 소리가 나는 방향이나 지도를 통해 대략 자신만의 방위를 만드는 것에 착안하여, 지능형 모바일 로봇에 음원추적 장치와 전자나침반을 장착함으로써 음원의 방향 또는 절대 방위를 기준으로 목표물을 찾아가는 알고리즘을 제시하고자 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.11a
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• pp.21-24
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• 2007

보안이 중요시되는 공간에서 임의의 사람을 추적하고 인식할 수 있는 시스템의 필요성이 점차 중요시되고 있다. 본 논문에서는 wide-area를 감시하기 위해 음원과 Pan-Tilt 카메라를 이용하여 침입자 추적 시스템을 구현하고자 한다. 먼저 음원 추적 센서를 이용하여 음원의 방위를 검출한 후 Pan-Tilt 카메라를 방위 방향으로 이동시키고 이동된 Pan-Tilt 카메라로부터 기준영상을 추출한 후 일정 기준 시간마다 영상을 다시 획득하여 차 영상과 검출결과를 얻어 침입자를 추적하여 감시 시스템을 구현한다. 본 논문에 의해서 구현된 시스템은 홈 네트워크 보안 시스템과 연동을 하여 가정이나 공공시설 보안에 대한 인터페이스 역할을 할 수 있다.

• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.76-82
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• 1997

The paper describes simulations and experimental results using a measuring system which utilizes the acoustic holographic method in order to exactly estimate an absolute position of a sound source. The measuring surface is installed to satisfy with a far field to the sound source and is composed of linear arrayed seven microphones. A measurement is simultaneously recorded by a reference microphone setting up a neighbour sound source and the linear arrayed seven microphones which are moved to the same interval. An absolute position of sound source is estimated by the cross-spectrum method to the received sounds between a reference and the measuring microphones. Phase differences of each microphone and time delays during scanning are compensated to the reference microphone and the measuring time of the first column. An optimal interval for each microphone in the measuring surface is decided by a numerical simulation. A source signal makes use of a sinusoid, and S/N ratio is 30dB in the experiment. The optimal microphone's interval in the simulation and the experiment is decided in order to satisfy with the Nyquist space sampling condition related to the wave length of 2kHz sinusoid. Mainlobe width of a estimated 3D hologram in the case of 2kHz source signal is decreased to 87% and 30% in comparison to 500Hz and 1kHz, and then a valid of simulation results is confirmed. Therefore, we verified a utilization of the study for a sound source estimation using 3ㅇ acoustic holographic method.

• Information Systems Review
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• v.16 no.3
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• pp.49-68
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• 2014

These days, consumers have increasingly preferred to digital real-time streamlining and downloading to listen to music because this is convenient and affordable for the consumers. Accordingly, sales of music in compact disk formats have steadily declined. In this regards, online digital music has become a new communication channel to listen musics, where digital files can be delivered over various online networks to people's computing devices. The majority of online digital music distributors has Music Recommender Systems for sales of digital music on their websites. Music Recommender Systems are parts of information filtering systems that provide the ratings or preferences that users give to music. Korean online digital music distributors have Music Recommender Systems. But those online music distributors didn't provide any rules or clear procedures that recommend music. Therefore, we raise important questions as follows: "Is Music Recommender Systems Fair?", "What is the impact of Music Recommender Systems on online music rankings and sales?" While previous studies have focused on usefulness of Music Recommender Systems, this study investigates not only fairness of Current Music Recommender Systems but also Relationship between Music Recommender Systems and online Music Charts. This study examines these issues based on Bandwagon effect, ranking effect, Slot effect theories. For our empirical analysis, we selected the most famous five online digital music distributors in terms of market shares. We found that all recommended music is exposed to the top of 'daily music charts' in online digital music distributors' websites. We collected music ranking data and recommended music data from 'daily music chart' during a one month. The result shows that online music recommender systems are not fair, since they mainly recommend particular music that supported by a specific music production company. In addition, the recommended music are always exposed to the top of music ranking charts. We also find that recommended music usually appear at the top 20 ranking charts within one or two days. Also, the most music in the top 50 or 100 ranks are the recommended music. Moreover, recommended music usually remain the ranking charts more than one month while non-recommended music often disappear at the ranking charts within two week. Our study provides an important implication to online music industry. Because music recommender systems and music ranking charts are closely related, music distributors may improperly use their recommender systems to boost the sales of music that related to their own companies. Therefore, online digital music distributor must clearly announce the rules and procedures about music recommender systems for the better music industry.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.2
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• pp.208-213
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• 2007

As recent research on home service robot has been performed actively in these days. It becomes very important for the robot to react upon voice and sound source, and then tracks an object position in dynamic environment like a home. When people choose a path for finding a destination of objects, in case of sound, they track a direction of the sound source. Or in case as a position of the object be girded with a point on map, people track the position according to absolute orientation of the present position and the sound source position. In this paper, In this manner we had views on what people decide own direction when they react one's voice or go some directions. We suggest a algorithm that intelligent mobile robots on which we installed a sound source tracking board and a digital magnetic compass board go some object's positions by the direction of sound source and absolute orientation.

• Journal of the Korea Society of Computer and Information
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• v.15 no.11
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• pp.91-99
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• 2010

Recently, recognizing user resource for personalized service has been needed in digital content service fields. Especially, to analyze user taste, recommend music and service music related information need recognition of user music file in case of online music service. Music related information service is offered through recognizing user music based on tag information. Recognition error has grown by weak points like changing and removing of tag information. Techniques of content based user music recognition with music signal itself are researched for solving upper problems. In this paper, we propose user music recognition on the internet by extracted feature from music signal. Features are extracted after suitable preprocessing for structure of content based user music recognition. Recognizing on music server consist of feature form are progressed with extracted feature. Through this, user music can be recognized independently of tag data. 600 music was collected and converted to each 5 music qualities for proving of proposed recognition. Converted 3000 experiment music on this method is used for recognition experiment on music server including 300,000 music. Average of recognition ratio was 85%. Weak points of tag based music recognition were overcome through proposed content based music recognition. Recognition performance of proposed method show a possibility that can be adapt to online music service in practice.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.241-244
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• 2002

시간영역에서의 음원 방향 추정 알고리즘을 이용하여 수동형 DIFAR Sonobuoy 의 도래각 추정 성능 평가 시스템을 구성하고 추정 오차에 대하여 고찰하였다. 일반 실내에서 음원주파수 $f_0(700Hz\~1.7kHz)$로 입사하는 음원에 대하여 도래각을 추정한 결과 한 주기당 한계 ${\pm}10^{\circ}$ 이내로 약 $80\%$ 이상 추정 결과로 나타났으며 특히, 1.7kHz 의 경우는 ${\pm}2.97^{\circ}$로 적은 오차를 보임에 따라 이 대역에서의 기준 주파수로 평가 시스템에 적용할 수 있음을 확인하였다.

• The Journal of the Acoustical Society of Korea
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• v.33 no.1
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• pp.60-67
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• 2014

The purpose of this study is to suggest a new concept of the absolute sound level system in order to basically solve all the irrational aspects from the mastering stage to the output stage during the process of producing a sound source. Through this absolute sound level system, all the input absolute sound levels of sound sources become standardized based on 60 dB(S), and then sound source producers can implement a sound level they intend by using the differential sound level tag. Besides, by matching the output absolute sound level with the input absolute sound level, a target sound level can be implemented as a listener intends. With this system introduced, sound source producers are able to focus on the completion of a sound source itself without an unnecessary competition for sound levels, and only by inputting the differential reduction tag, they can implement a sound level balance as intended. At the same time, listeners are able to appreciate all kinds of sound sources fit for the standard of absolute s ound levels they want to listen to, without a process of trial and error, no matter what kinds of listening environments and sound systems they have.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.660-669
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• 2003

This paper describes a theory to calculate sound source field from the spatial transform of sound field and the measured cross-power spectrum of sound pressure over a hologram plane close to a sound source, Calculating method is proposed to solve sound pressures from cross-power spectrums over a hologram plane, For this, Taylor series for the nonlinear equations is expanded, and it is calculated using Newton-Raphon method, Also, a wave number filter is used to reduce errors that is occurred on the backward propagation, and is performed numerical simulation of the circular piston sound source with infinite baffle in water to verify the proposed theory.