• Journal of Ship and Ocean Technology
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• v.8 no.3
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• pp.18-25
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• 2004

Sound reception system is required to detect the sound and the quadrantal direction of the other ship's horn sound, to overcome the effects of enclosed wall for navigation space, functioning as a sound barrier. However, the realized systems can only provide quadrantal information of the other ship. This paper presents a new arrangement of microphones, having geometrically symmetric deployment with the same distances between sensors and the same angles between adjacent sensors with respect to the geometrical center. The sound pressures received at microphones are transformed into the related envelope signals by applying Hilbert transform. The time delays between microphones are estimated by the correlation functions between the derived envelope signals. This envelope base processing mitigates the noises related to the reflection by ship and sea surface. Then, the directional information is easily defined by using the estimated time delays. The suggested method is verified by the generated signals using boundary element method for a small ship model with sea surface wave. The estimated direction is quite similar to the true one and therefore the proposed approach can be used as an efficient sound reception system.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1125-1130
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• 2014

In this paper, we propose a sound reception system against surrounding noise for ships based on digital signal processing technologies. In order to suppress unwanted surrounding noises, a digital band-pass filter is designed, which the pass-band of the filter is between 70Hz to 820Hz. Also, we develope a sound direction indicating algorithm with 4 microphones. After filtering the audio signals from 4 microphones, the developed sound direction indicating algorithm can indicate 8 directions. In addition, we implement prototype board for the sound reception using a digital signal processor chip and audio codecs, and verify the proposed algorithm.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.836-842
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• 2023

Under the Welfare of Disabled Persons Act, the national qualification test allows disabled and non-disabled people to appear for the same test, and the deaf do not fall under the reason for disqualification from obtaining a license for power-driven water leisure crafts; therefore, even the deaf can obtain a license. During a risk of collision at sea, ships and power-driven water leisure crafts notify the other party of dangerous signals such as maneuvering and warning signals through sound signals to prevent accidents that may occur because surrounding ships are not visible. However, a method is required to prevent marine accidents that may occur when the deaf cannot hear danger signals through sounds from nearby ships or power-driven water leisure crafts during leisure activities owing to hearing impairment. A sound reception system is a device installed on a ship where missionary work is completely deposed to display the amplification of external sounds and the direction of sound reception on the screen. Through visual display of sound signals such as dangerous signals that cannot be heard owing to hearing impairment, improvement measures were proposed to prevent marine accidents that can occur owing to the inability of the deaf to check sound signals during leisure activities.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.83-90
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• 2017

In this paper, a sound reception system using a phase difference of whistle signals is proposed and analyzed based on spectral analysis. The proposed system receives whistle signals from four microphones installed in four different directions with 90-degree intervals between them. The proposed algorithm detects the phase of each received signal based on spectral analysis and estimates the direction of the whistle signal by obtaining the phase difference between the received signals from two adjacent microphones. Furthermore, we theoretically analyze the phase difference between two adjacent received signals according to their arrival angles and implement the proposed system using a DSP chip. In addition, the operation of the proposed algorithm are verified using the implemented system in a laboratory environment. Experimental results show that the proposed scheme can well estimate the direction of the whistle signal.

• Journal of Ocean Engineering and Technology
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• v.34 no.3
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• pp.227-236
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• 2020

Underwater acoustics, which is the domain that addresses phenomena related to the generation, propagation, and reception of sound waves in water, has been applied mainly in the research on the use of sound navigation and ranging (SONAR) systems for underwater communication, target detection, investigation of marine resources and environment mapping, and measurement and analysis of sound sources in water. The main objective of remote sensing based on underwater acoustics is to indirectly acquire information on underwater targets of interest using acoustic data. Meanwhile, highly advanced data-driven machine-learning techniques are being used in various ways in the processes of acquiring information from acoustic data. The related theoretical background is introduced in the first part of this paper (Yang et al., 2020). This paper reviews machine-learning applications in passive SONAR signal-processing tasks including target detection/identification and localization.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.990-997
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• 2007

In the last 5 years, collisions of fishing vessels have recorded about 54.6% of the total marine accidents. Specially about 64.0% of these collisions were caused by navigator's negligence of watch keeping during works. The purpose of this paper is to develop vessel detecting system that is able to receive the whistle blast of other vessel and make a warning sound and light when the fishermen can not confirm the approaching another vessel on account of fishing works. It is designed to receive the whistle signal blast by a weather tight microphone. The signal is processed by analog active filter in order to enhance the SNR(Signal to noise ratio). And this microprocessor-based system is programmed to do ADC(Analog to digital converting), FFT analysis, controls of warning sound and light.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.91-97
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• 2015

In this paper, wireless communication from a smart phone to a hearing aid using audible frequency band sound was considered. 1kHz single channel carrier frequency was applied for amplitude shift keying (ASK) binary data modulation, and the result of the transmission and reception was tested. The overall system process was precisely explained and experimentally evaluated. The result will be applied for realizing a digital hearing aid with remote control feature by a smart phone.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.41-45
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• 2006

The fabrication process of fiber placement system of carbon fiber reinforced plastic (CFRP) requires real time process control and reliable inspection to ensure quality by preventing defects such as delamination and void. Therefore, novel non-contact inspection technique is required during the non-destructive evaluation in a fiber placement system. For the inspection of delamination in CFRP, various methods to receive laser-generated ultrasound were applied by using piezoelectric transducer, air-coupled transducer, wavelet transform and scanning laser ultrasonic technique. Laser-generated ultrasound was received with a conventional piezoelectric sensor in contacting manner. Then signal characteristics due to defects were analyzed to find a factor for detecting defects. Air-coupled transducer was used for reception of laser-generated guided wave using linear slit array in order to generate high frequency guided wave. And line scan technique was used to confirm the capability of on-line application. The high frequency component of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled transducer. The first peak of the frequency spectrum under 100kHz in the delamination region is higher than in the sound region. By using this feature, the line scanned frequency data were acquired in fully non-contact generation and reception of ultrasound. This method was proved as useful technique for detecting delamination in CFRP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.201-208
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• 2001

In the 21 st century, broadcasting, communication, and computer have been integrated due to the development of digital technology. Accordingly, to overcome the limit of respective communication media and to maintain them, their independent area shall not be classified. This study is to examine the future environment of digital TV broadcasting, to analyze customizing type service and interactive type TV technology, and to make asymmetric interactive digital TV publication broadcasting system, which is TV broadcasting in the next generation to treat visual image, sound, and various data all together by harmonizing broadcasting and communication like ISDB(Integrate Service Digital Broadcasting). In addition, to develop service on publication broadcasting with high quality, this study is tn propose to develop relative devices for TV/PC reception to realize a new communication type TV publication broadcasting, by analyzing technology for producing, sending, transmitting, receiving, and saving to apply to customizing type interactive system and by examining its application.

• Hwankyungkyoyuk
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• v.15 no.2
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• pp.86-99
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• 2002

The purpose of this study is to make clear the management of Environmental Education in Elementary school in Korea. To accomplish this purpose, The research for the actual condition of management of Environmental Education according to school, grade, and class was progressed. The researcher was analyzed Hindrance Factors of Sound Environmental Education in School and presented some suggestion on the basis of above-mentioned findings. On one side, the method of research is a case study on qualitative based way. A case study was conducted with it's focus on public elementary school in Seoul. As for major research methods, observation by participating in school field and in-depth interview were respectively employed; subsidiary methods included literature study. The findings of this study are as belows: First, Environmental Education was not managed practically with specific way in school. Second, Environmental Education by direct and actual outdoor experience was unusual. Third, most of class school work about Environmental Education was focused on not only the type of prescription after the environmental problem but also, the treatment of articles in newspaper and TV. Forth, educational compulsion such as “you have to do that.” was mainly used as Environmental guidance for sound attitude in school without clear reasons. In the last analysis, hindrance factors of sound management for environmental education in elementary schools were ‘passive adjustment’, ‘discriminative reception’, ‘absence of information resource’. these factors came from atmosphere of negligence environmental education in schools. Therefore, all of teachers have to affirmative belief and attitude as personal dimension and all of elementary schools improve environmental education system.