• Journal of the Korean Wood Science and Technology
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• v.26 no.4
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• pp.26-33
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• 1998

Acoustical properties of chestnut and paulownia woods have been determined in four film thicknesses of oriental lacquering and cashew varnishing on double surfaces of soundboard to elucidate effects of finishing. Accelerometer was attached to the specimen at one third position from one end, and specimen was hit by the impact hammer at one third position from opposite end. Data were processed by vibration analyzer. The ratio of axial-to-transverse sound velocity of untreated specimens of chestnut and paulownia were 3.25 and 5.34, respectively. Natural frequency, specific Young's modulus, acoustical coefficient, sound velocity, damping of sound radiation(DSR) and acoustical converting efficiency(ACE) decreased by oriental lacquering and cashew varnishing for both species. Damping of internal friction of chestnut decreased by oriental lacquering and cashew varnishing, but that of paulownia increased. Natural frequency. specific Young's modulus, acoustical coefficient, sound velocity, and DSR decreased with increased film thickness of both finishing materials. However, damping of internal friction and ACE showed irregular tendency with increased film thickness. Acoustical properties of cashew varnished chestnut specimen were better than those of oriental lacquered specimen. Acoustical properties of oriental lacquered paulownia specimen were better than those of cashew varnished specimen.

• Survey Research
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• v.11 no.2
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• pp.29-44
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• 2010

The aim of this study was to determine principal non-acoustical factors for noise annoyance in the vicinity of Kimpo Airport in Seoul, Korea. Noise annoyance was estimated using self-reported annoyance scale. We have conducted a social survey aiming to identify the main sound sources, evaluate the annoyance and analyse the main effects of noise on people. Acoustical and non-acoustical variables are expected to greatly affect annoyance responses. This study divided acoustical variables into aircraft, road traffic and neighboring noises, and non-acoustical variables into demographic, situational and attitudinal variables. The study performed multiple regression analysis to determine the influences each variable has on annoyance responses. Acoustical variables affect noise annoyance to aircraft and neighboring noise except road traffic noise. For road traffic and neighboring noise annoyance was affected by non-acoustical variable, insulation by housing type. For aircraft noise, main noise source of this area, annoyance was affected by acoustical variable and some non-acoustical variables, mainly exposure time.

• Proceedings of the Acoustical Society of Korea Conference
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• 1985.10a
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• pp.9-12
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• 1985

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.180-184
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• 1992

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.231-234
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• 1998

• Proceedings of the Acoustical Society of Korea Conference
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• 1987.11a
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• pp.13-16
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• 1987

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.1-10
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• 1998

Lots of techniques are adopted for a flame stabilization and a high-load combustion. But the techniques being used were passive control method which have to change combustor shape like pilot flame, flame stabilizer, pressure profile, etc. Active control method which is not necessary to transform its shape is employed. Acoustical excitation is broadly used for its convenience in changing frequency and intensity. Both acoustical excitation and flame stabilizers were adopted to study their relationship. So, we investigated flammability limits. Flame visualization. And mean temperature in the condition of various frequencies, intensities, and flame stabilizers. As a consequence, flammability limit were advanced in acoustically excited flame at some frequencies. Coherent structure was extended to the downstream region through acoustical excitation and a size of vortice was curtailed. Also width of recirculation zone was magnified. In addition, Effects of acoustical excitation was stood out at 25mm flame stabilizer rather than another ones.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.722-727
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• 1994

In two previous papers [1], [2], we presented the validity of a method that calculated the Leq values along High Speed Train (TGV in french) lines from the level/time evolution of moving trains. Tanks to this method, it is now possible to compute specific time-related effects such as interactions between train bodies and close obstacles. This paper lists important parameters to be considered within TGV studies and presents the various levels of study, starting from the research of the best traject (extensive studies), passing through noise impact studies (intensive studies) of the chosen traject to the dimensionning of antinoise devices (final design), and all this to guarantee precise respect of noise criteria. A theoretical comparison study conducted on about 80 different types of antinoise devices including earthberms and noise barriers of different forms, dimensions and materials is also presented. At last a "final design" study using all benefits of the method (full 3D and time representation) is presented.presented.

• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.51-60
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• 2009

This paper presents a new method of designing room equalization filters using a warped common acoustical pole and zero (WCAPZ) modeling. The proposed method is capable of significantly reducing the order of the equalization filters without sacrificing the filter performance, especially, at low frequencies. Thus, the associated input-output delay is much smaller than the conventional block transform method while its computational complexity is comparable to it. The computational complexity also is still comparable to the conventional room equalization method, since the filter is implemented in the linear frequency domain after the pole-zero dewarping. Simulation results confirm that the use of the proposed algorithm significantly improves the room equalization over a range of low frequencies.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1070-1077
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• 2011

This study intends to assess the defect in the weld zone of titanium grade 2 plate in terms of acoustical anisotropy based on the angle beam method. Depending on the rolling direction, the ratio of wave velocity was found to be 1.08 and the difference in the angle of refraction was more than seven degrees, confirming the presence of acoustical anisotropy. Thus for measuring the length of defect in the weld zone of the titanium plate (thickness of 10mm), the distance amplitude characteristics curves of titanium, TDACC-R and TDACC-T were constructed for the measurements in consideration of the acoustical anisotropy on CRT of the ultrasonic testing equipment. As a result, when the distance amplitude characteristics curve corresponds to the rolling direction, the length of defect was close to the actual measurement within 1mm and when different, the difference was found to be over 4mm. It was affirmed that the acoustical anisotropy should be taken into consideration when measuring the length of defects in the weld zone of the titanium plate with the presence of acoustical anisotropy.