• The Journal of the Acoustical Society of Korea
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• v.42 no.4
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• pp.271-284
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• 2023

This study compared 431 acoustic terminology of South Korean industrial standards and North Korean national standards based on IEC 60050-801:1994 international standards. In addition, this study attempted to integrate acoustic terminology between the two Koreas. There were 139 (32.3 %) AA types with exactly the same form of terminology, 35 (8.1 %) Aa types with different spellings due to differences in linguistic norms, and 257 (59.6 %) AB types with completely different forms. Morphologically, there were more than twice as many different types of terminology as the same type. In the integration of acoustic terminology with different forms, 178 (61 %) North Korean terminology and 76 (26 %) South Korean terminology were adopted. we would like to overcome the limitations of this study through the following suggestions. First, the government should support academic exchanges between the two Koreas and encourage the establishment of common standards for acoustic terminology. Second, efforts should be made to share acoustic terminology data between the two Koreas and publish an integrated acoustic terminology dictionary. Third, South and North Korea should jointly launch a terminology committee to make efforts to revise international standards together.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.189-202
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• 2023

In this study, the acoustic performance was analyzed by architectural shapes of the hall. There are four architectural shapes of halls. They are rectangular, horseshoe, surround, and fan-shape. Eight acoustic parameters were used to determine the acoustic performance. These are RT₆₀, EDT, C₈₀, BQI, LF, G_mid, G₁₂₅ and ITDG. First, measurement data of famous concert halls around the world were analyzed. The correlation coefficient R was obtained by regression analysis of the relationship between the subjective ranking of the halls and the acoustic parameters. It was found that BQI, G, and ITDG have higher correlation coefficients R. Also the average of acoustic parameters for each architectural shape were obtained. The total acoustic performance for each shape was calculated by using the correlation coefficient R as a weight for each acoustic parameters. As a result, rectangular halls and horseshoe halls showed good acoustical performances. Second, 3D models of each architectural shape were created and acoustic simulation had been performed. The simulation was performed by creating 3D models of each four shapes of concert halls with the same volume and sound absorption coefficient. Listening test was carried out using the sound source which is created from impulse responses of 3D model. As a result, rectangular hall and horseshoe hall showed the best performance however surround hall and fan-shaped hall showed relatively poor performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.91-98
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• 2003

In the structural analysis of a launch vehicle, the construction of loading functions and the determination of responses to them are very important. Among many kinds of loads, acoustic load generated by exhaust is a random load that can be described in a statistical manner. In this study, loading functions corresponding to the acoustic loads are constructed and applied to the structural analysis of launch vehicle. Acoustic loading functions are constructed using source allocation method. Structural analyses are carried out by using finite element modelling and frequency response function of finite element model. The stresses resulting from acoustic loads and acceleration power spectral density functions at interfaces of each section are calculated. These analyses are essential for the development of environmental test specifications and associated dynamic design requirements which are necessary to ensure overall vehicle reliability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.10-18
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• 2008

This paper presents the design and imelementation of an electronic ballast with a passive PFC structure from which acoustic resonance of the metal halide lamp was removed by introducing the frequency modulation(FM) method. The proposed ballast consists of an EMI filter, passive PFC circuit full-bridge inverter, LC resonance type igniter and a circuit for removing acoustic resonance. The FM method solved two problems associated with single frequency driving: variation of the acoustic resonance range according to lamp aging and the acoustic resonance range discrepancy caused by different materials sealed inside the arc tube and their pressures for arc tubes of identical sizes from different manufacturers. Performance of the prototype developed for this study of the electronic ballast for 1[kW] metal halide lamp was verified by evaluating its optical conversion efficiency, input PF, input current THD and power conversion efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.336-342
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• 2017

Recently, there has been an increasing need for underwater communication systems to monitor ocean environments and prevent marine disasters, as well as to secure ocean resources. Most underwater communication systems adopted acoustic communication with a consideration of attenuation, absorption, and scattering in conductive sea water, and developed fully digital modems based on processors. In this study, a digital up converter (DUC) and a digital down converter (DDC) was developed for an underwater basestation based on underwater acoustic communication systems. Because one of the most important issues in underwater acoustic communication systems is low power consumption due to environmental problems, this study developed a specific hardware module for DUC and DDC. It supported four links of underwater acoustic communication systems and converted the sampling rate and frequency. The systemwas designed and verified using Verilog-HDL in ModelSim environment with the test data generated from baseband layer parts for an underwater base station.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.309-317
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• 2000

Demand for new nondestructive evaluations is growing to detect tensile crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we investigated the strength of fire resistance steel for frame structure by tensile test after degradation treatment and analysed acoustic emission signals obtained from tensile test with time frequency analysis methods. In the T and TN specimens(under $600^{\circ}C$-10min ) consisting of ferrite and pearlite structure, most of acoustic emission events were produced near yield point, mainly due to the dislocation activities during the deformation. However, B specimen under $600^{\circ}C$-10min had a two peak which was attribute to the presence of martensite phase. The first peak is before yield point and the second after yield point. The sources of second acoustic emission peak were the debonding of martensite-martensite interface and the micro-cracking of brittle martensite phase. In $600^{\circ}C$-30min to $700^{\circ}C$-60min, many signals were observed before yield point and were decreased after yield point.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1615-1626
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• 1992

In this study, vibrations and resulting acoustic radiations from an elastic beam impacted by a steel ball were studied theoretically and experimentally. First the transverse vibrations of free-free elastic beams are analysed with modal analysis technique. The impact forces are modeled with the Hertz's theory and the contanct duration is compared with the measured values. Also the calculated beam vibrations are verified with the experimental results. Then the acoustic radiations due to the beam vibration are studied numberically and experimentally. The acousticpressure is calculated assuming the beam has an elliptical cross-section. The predicted acoustic pressure is compared with the measured value. It was found that both the predicted beamvibrations using the Hertz's theory and the estimated acoustic pressure under the assumption of an elliptical cross- section are in very good agreements with the measured values.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.10 no.2
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• pp.135-139
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• 1999

Objectives : The purpose of this study was to systematically analyze and compare the acoustic characteristics of vocal major students with vocal nodule when singing. Materials and Methods : Ten sopranos with vocal nodule, who have never been treated due to voice problems, were the subject group. Twenty healthy sopranos major students were the control group for this study. The vocal nodule was confirmed by stroboscopy and the acoustic and electroglottographic analysis was conducted on be groups. Additionally, an inquiry on usual voice problems during speaking and singing were performed on each of the groups. Results : The vowel /a/ was spoken and sung by sopranos of each group. There were no significant differences in Fo, jitter, shimmer, NHR at speaking and singing in either group. We did not register any significant differences of closed quotient and speed quotient in electroglottography for both groups at singing, but speed quotient was increased in subject group at speaking(p＜0.05). And the sopranos with nodule demonstrated voice fatigue(70%), strained and tired voice after long period of performance and conversation(60%) on inquiry. Conclusions : Although they had a vocal nodule, this group, who had a long period of voice training, did not present any differences in acoustic and electroglottographic problems during short performance, but, the vocalists noticed delicate voice problems after a long performance. We conclude that the voice training teacher and laryngologist must initiate voice management and speech therapy for vocal nodule, even if there is no specific abnormality in acoustic analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.11
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• pp.833-839
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• 2014

The shooting noise caused by shooting training, which has strength and impacts, is becoming a serious damage to the residents around the shooting range and, consequently, the number of civil appeals against the shooting noise is on the constant increase. For this reason, the military examines the effects of the shooting noise at the stage of design in constructing a shooting range and tries to build a soundproof shooting range to minimize civil appeals. However, the lack of research and data concerning propagation and attenuation, both of which characterize the shooting noise from within a soundproof shooting range, even makes it so difficult to design a soundproof shooting range in constructing it. So this study used an acoustic simulation in a soundproof shooting range to identify acoustic and propagation characteristics within the shooting range and, on this basis, predicted the noise level at an exit of the soundproof shooting range. As a result, if the form and specifications of a soundproof shooting range were decided on at the stage of design, it was possible to use a simulation to design a soundproof shooting range with optimized acoustic performance and, on this basis, to predict a sound pressure level at an exit of the soundproof shooting range. On the basis of these data, it is probably possible to determine the degree of the effects of the shooting noise on the villages around a shooting range and the extent of damage to it and to minimize civil appeals against the shooting noise and resolve the issues of compensation and agreement with ease. This study is expected to provide useful data for designing and constructing a similar soundproof shooting range.

• The Journal of the Acoustical Society of Korea
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• v.41 no.1
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• pp.1-8
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• 2022

This paper identifies the cause of the high frequency calibration limit of the acoustic chamber type calibrator for microphone calibration and presents a method to improve it. By using a commercial finite element analysis software, we analyzed the calibration frequency limit of the acoustic chamber type calibrator through eigen-frequency and frequency domain analysis. Based on this, we designed and fabricated an acoustic chamber type calibrator that can precisely calibrate within 1 dB from about 2 Hz to 6.4 kHz and verified its performance through experiments. The acoustic chamber type calibrator fabricated through this study has the advantage of being able to calibrate multiple microphones simultaneously in a wide frequency range, so it can be usefully used for simple calibration for multiple microphones.