• The Journal of the Convergence on Culture Technology
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• v.10 no.6
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• pp.197-204
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• 2024

This study investigates the key application technologies for military loudspeakers and examines their operational cases in conjunction with the Korean military, foreign militaries, and other weapon systems. The purpose of this research is to propose major considerations and strategies for the optimal operation of loudspeakers tailored to military operational environments, thereby enhancing the efficiency and effectiveness of military operations.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.3
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• pp.220-227
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• 1995

An underwater speaker was designed and used as sound source for thronging shoal of squid in squid angling gear operation. The frequency characteristics of the designed speaker was analyzed experimentally and the thronging response of shoals of squid which may be a key parameter for a new sound catching method, was characterized in audible frequency. The field experiment was carried out in the coast of Cheju Island. The results of this study are summarized as follows; 1. Amplitude response of the speaker shows a maximum in their the frequency of 500Hz. 2. The output waveform distortion is not measured in the frequency range of 250~600Hz. 3. A underwater noise of shoals of squid which were thronged by fish lamp in night appeared the center frequency of 300~400Hz. 4. The shoals of squid shows a thronging response, when a manufactured underwater speaker transmits a intermittent audible sound of 300~400Hz in 10m depth of water.

• Fire Science and Engineering
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• v.33 no.1
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• pp.105-112
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• 2019

In this study, an architectural acoustics simulation was conducted to examine the clear and uniform transmission of emergency broadcasting sound in a T junction corridor space. The sound absorption performance of the corridor space and the location and spacing of the loudspeaker for emergency broadcasting were varied. The distribution of the sound pressure level and the distribution of sound transmission indices (STI, RASTI) were compared. The simulation showed that the loudspeaker for emergency broadcasting should be installed approximately 10 m from the center of the T junction corridor connection for clear voice transmission. Narrowing the 25 m installation interval of the NFSC shows that an even clearer and sufficient volume of emergency broadcast sound can be delivered evenly.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.153-160
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• 2023

This research experiments on the workers' recognition of the fire alarm sound for sirens and portable loudspeakers in a small construction site. As a result of analyzing the siren alarm sound recognition from measuring on the 1st, 2nd, and 4th floors, the sound was more unrecognizable on the 4th floor than on the 1st, and 1 person on the 1st floor was unable to recognize all sounds. In the case of the 2nd floor, one person could not notice the alarm in the last 3rd trial, and another did not realize it all three times. For the 4th floor, 3 people demonstrated unrecognition in all 3 tests. As a result of analyzing the recognition of portable loudspeaker alarm sounds, 1 person could not recognize all sounds on the first floor. In the case of the 2nd floor, 2 people were confirmed to be unable to notice, and lastly, 4 people could not recognize all trials on the 4th floor. The subjects who didn't recognize the sound were unable to distinguish between portable loudspeaker alarm sound and work noise due to the workspace and obstacles.

• Journal of the KSME
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• v.27 no.5
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• pp.421-427
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• 1987

공력소음은 공기역학적 힘에 의해서나 또는 유동 내에서의 난류와 같은 유체운동에 의해서만 발 생되는 소리와 관계되며, 진동하는 바이올린 줄이나 확성기의 진동에 의해서 발생되는 즉, 고체 표면의 진동에 의해서 발생되는 고전적인 음향학과는 무관하다. 그리고 여기서는 주로 공력 소음문제를 다루되 자세하고 엄밀한 수학적 전개보다는, 간단한 실제적인 예를 들어서, 물리적 메카니즘을 가능한 한 자세히 기술하여 공력 소음의 이해를 돕고자 하였다. 또한 오래된 고전적 방법을 가능한 한 피하고 최근의 방법으로 설명하도록 하였다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.10a
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• pp.47-48
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• 2002

바다 속에서의 소음은 해풍, 파랑, 강우 등 자연소음과 어류의 생식음, 신호음, 식이음 등 생물이 내는 음과 선박의 엔진 등과 같은 인공음이 있는데 수중가청음을 이용한 어군의 유집은 어장 조업 시에는 조업 능률을 향상시키고, 축양 어업에서는 음향 제어에 의한 자동급이와 치자어의 육성단계에서부터 음향순치를 통해 어류를 일정한 해역에 정착, 서식하도록 할 수 있어 해양목장화 등 여러 면에 응용이 되어지고 있다. (중략)

• Fire Science and Engineering
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• v.33 no.6
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• pp.186-189
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• 2019

NFSC 202 stipulates that if a loudspeaker or wiring on one floor of a building is shorted because of fire, it should not interfere with the fire notification on the other floors. To address this problem, this study proposes an ultrasonic transmitter/receiver consisting of an ADC, HPF, and LPF in an emergency broadcasting system that can operate regardless of the volume level of the amplifier output loudspeaker capacity. After transmitting the transmission frequency at -12 dB (110 kHz), it is received at -18 dB by transmitting -12 dB in case of short circuit depending on the frequency characteristics. Typically, depending on the loudspeaker capacity, it is received from -24 dB to -66 dB. In case of disconnection, it exceeds -66 dB and no data are received. It is also possible to check the track status during fire or general broadcasting. Thus, it was confirmed that the system is suitable for NFSC 202 regulations. Furthermore, as the current system is replaced, the inspection or test criteria should be amended or revised.

• Fire Science and Engineering
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• v.32 no.4
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• pp.42-49
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• 2018

In this study, in order to investigate whether or not the emergency broadcasting sound generated from an emergency broadcasting speaker is clearly transmitted to the occupant through architectural sound simulation, when the loudspeaker for emergency broadcasting is installed at intervals of 25 m according to NFSC 202 for a rectangular hallway. The sound pressure level and speech intelligibility index were analyzed according to changes in building finishing materials. With a reflective material finishing, sound pressure level satisfied the standard while speech intelligibility index was low. As a result of applying the sound absorbing material finishing, clarity and speech transmission index was improved to a level that could be understood by the occupant, whereas the sound pressure level delivered to the occupant decreased in the same space.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.3-10
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• 1999

Investigations of temperature differences between both cnds of thermoacoustic exchanger generated by acoustic heat transport have been carried out as a function of the position of TAC(Thermo-Acoustic Couple)[1] in a 68-cm-long duct. Fixed with the electric power at 50W, measurements were compared with the theory changing the frequency from 150Hz to 300Hz with 10Hz step. The frequency-position dependent distribution of temperature difference corresponding to the Q-values was obtained with the numerical simulation. Through this distribution, the optimum position of the thermoacoustic exchanger and the optimum driving frequency can be determined.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.2
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• pp.16-22
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• 1973

It is described about radiation monitor which can be used for rapidly checking the contamination caused by gamma and beta radiation. and for constantly monitoring such a probable hazardous area. In the circuits used in this device, a detailed analysis on the pulse amplifier and the design formulae of the discriminator circuit is presented. The device is all transistorized and the counting rates are audible through speaker besides being read by meter to the extent of maximum 10 k pps.