• Journal of the Korean Society of Clothing and Textiles
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• v.6 no.1
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• pp.61-66
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• 1982

Succeeding to Report 1, to compare folded curtain fabrics with curtain fabrics, the sound pressure level (SPL) of folded curtain fabrics were measured by sound level meter. Transmission coefficient was calculated by the ratio of incidence sound intensity and transmission sound intensity. The relationship between these values and factors (drape coefficient, porosity) relating to the structure of curtain fabrics were investigated experimentally. The following results were obtained: 1. The transmission coefficient by ratio of sound pressure level was lower than that by ratio of sound intensity. 2. In folded curtain fabrics, difference of SPL was smaller and transmission coefficient generally decreased. 3. The relation between the porosity and transmission coefficient of curtain fabrics is given as plus correlation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1273-1279
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• 2001

Precise highway traffic noise simulation and reduction require the accurate data for sound power levels emitted by vehicles, varied to road surface, traffic speed, vehicle types and makers, different from countries to countries. In this study, we have elaboratively measured domestic highway traffic noise and parameters affecting noise levels at the nearside carriageway edge. From numerical simulation using the measured results for highway traffic noise, we propose not only two correction factors to enhance the accuracy of highway traffic sound power estimation using ASJ Model-1998 but also its typical power spectrum according to road surface type. The measured and predicted highway traffic noise levels using the proposed sound power shows little difference within 1 dB.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.554-558
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• 2004

In this paper, we introduce noise prediction program of HVAC system to assist low-noisy design of ship's cabin. The developed program calculates sound power levels at HVAC components considering primary and secondary noise generated by fan and duct element, duct element noise attenuation, and duct break-in noise based on the authentic empirical method suggested by NEBB and acoustic power balancing method. Sound pressure level at cabin with or without ceiling system is evaluated by the diffuse-field theory considering diffuser and duct break-out sound powers. Moreover, the program provides intuitive pre- and post-processors using modem GUI functions to help efficient modeling and evaluation of cabin and HVAC component noise. To validate the accuracy and convenience of the program, noise prediction for a HVAC system is demonstrated.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.158-163
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• 2012

Recently, reducing underwater radiated noise (URN) of ships has become an environmental issue to protect marine wildlife. URN of ships can be predicted by various methods considering its generating mechanism and frequency ranges. For URN prediction due to ship structural vibration in low frequency range, the fluid-structure interaction analysis technique based on finite element and boundary element methods (FE/BEM) is regarded as an useful technique. In this paper, URN due to a double bottom-shaped structure vibration has been numerically investigated based on a coupled method of FE/BEM to enhance the prediction accuracy of URN due to the vibration of real ship engine room structure. Acoustic radiation efficiency and URN transfer function in case of vertical harmonic excitation on the top plate of double bottom structure have been evaluated. Using the results, the validity of an existing empirical formula for acoustic radiation efficiency estimation and a simple URN transfer function, which are usually adopted for URN assessment in initial design stage, is discussed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.307-312
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• 2018

In this paper, we can confirm the result of intuitive interface software implementation for operating a digital PA(Public Address) controller and the performance of audio mixer control part. Developed user interface software provides the maintaining management and control function of digital hybrid mixer. This SW loaded in the integrated control server controls an sound status of the audio mixer TAD-168M and checks the device status for Public Address integrated system. Also, this SW enables the integrated control and the continuous upgrade. Developed SW is connected to TAD-168M with Ethernet and linked to PC Lan port and the 4-port switch, located in the backside of TAD-168M, by LAN cable for communicating with operating PC. Integrated control including system management, audio control and uplink broadcasting control for broadcasting system will be made available with this novel developed system.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.33-40
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• 1996

In this paper, we resolved a trade-off problem of the blind equalizer based on the stop-and-go algorithm that is commonly used for QAM demodulation in CATV receiver. The stop-and-go algorithm has used the LMS(least mean square) algorithm in the updating operation of tap weights so that the structure of equalizer is simple, but there is a trade-off between convergence speed and steady state error as in the typical LMS algorithm. We used the variable step size algrithm to improve the convergence speed with the steady state error in the constant level. With respect to the same level of the steady state error, the variable step size stop-and-go algortihm improved convergence speed by about $36%{\sim}56%$ as compared with that of the constant step size algortihm.

• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.98-104
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• 2020

A method to reduce the Contraction and Expansion (CE) noise occurred in an air conditioner is investigated. The noise is measured during the cooling and heating phases in a temperature and humidity chamber to identify the generating phenomenon of CE noise of the air conditioner and the decomposition method is used to estimate its occurrence location. The CE noise of an air conditioner is known to be caused by a stick-slip phenomenon generated by joints of parts connected to the lower decor. Thus a friction experiment was conducted to investigate noise inducing factors. Also, this study established evaluation criteria to effectively analyze the results from friction experiments. Experimental results indicate that increasing surface roughness on both sides of joints is effective. Accordingly, the effect of increased surface roughness on joints of upper and lower decor of air conditioners is evaluated to see its feasibility in a temperature and humidity chamber.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.167-173
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• 2009

Bathymetry survey around the Baengnyeong-do was made by the Korea Hydrographic and Oceanographic Administration (KHOA), using the Simrad EM3000 Multi-Beam EchoSounder (MBES) mounted at the hull of the R/V Badaro 1. Sound velocity were monitored with frequent sound velocity profiler(SVP) casts during the acoustic measurements. The depth distribution and fluctuation of thermocline varied locally owing to the effect of several current flows such as Kuroshio current and Yellow sea coastal waters. These uncertainties cause the falling-off in accuracy of MBES results. In this paper, the bathymetry results will be presented and their accuracy will be discussed along with comparisons to the time and spatial variations in sound velocity profile.

• Science of Emotion and Sensibility
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• v.4 no.2
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• pp.79-88
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• 2001

The objectives of this study were to investigate the relationship of sound parameters with subjective sensation and physiological responses, and to figure out the interrelationship between the subjective sensation and physiological responses. Sound parameters calculated were LPT, ΔL, Δf, loudness[Z], and sharpness[Z]. Subjective sensation was evaluated in 7 aspects(soft-hard, loud-quiet, pleasant-unpleasant, sharp-dull, clear-obscure, rough-smooth, high-low) by thirty participants. We acquired physiological responses when each fabric sound was presented to 10 participants. Physiological signals obtained in this study were electroencephalogram(EEG), pulse volume(PV), skin conductance level(SCL), and LF/HF of heart rate variability. The larger the values of loudness[Z] and LPT, the louder and the rougher the subjective sensation of the perceived fabric sound. Also, the larger the values of loudness[Z] and LPT, the harder, the duller, and the less pleasant. As LPT increased, PV decreased. Loudness[Z] increased in proportion to SCL and so did sharpness[Z] to LF/HF. As the sound perceived to be quieter and clearer, the relative power of slow alpha rose. As the sound perceived to be more pleasant and smoother, PV rose.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.130-140
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• 2022

Recently, wideband acoustic technology has been introduced and started to be used in fisheries acoustic surveys in various waters worldwide. Wideband acoustic data provides high vertical resolution, high signal-to-noise ratio and continuous frequency characteristics over a wide frequency range for species identification. In this study, the main characteristics of wideband acoustic systems were elaborated, and a general methodology for wideband acoustic data analysis was presented using data collected in frequency modulation mode for the first time in Republic of Korea. In particular, this study described the data recording method using the mission planner of the wideband autonomous acoustic system, wideband acoustic data signal processing, calibration and the wideband frequency response graph. Since wideband acoustic systems are currently installed on many training and research vessels, it is expected that the results of this study can be used as basic knowledge for fisheries acoustic research using the state-of-the-art system.