• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.883-889
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• 2011

The brand sound of vehicle diesel engine is recently one of the important advantage strategies in the automotive company. Because various noise components masked under high frequency level can be audible in quieter driving situation. Many researches have been carried out for subjective and objective assessments on vehicle sounds and noises. In particular, the interior sound quality has been one of research fields that can give high quality feature to vehicle products. Vehicle interior noise above 500 Hz is usually controlled by sound package parts. The materials and geometries of sound package parts directly affect on this high frequency noise. This paper describes the sound quality evaluation method for the vehicle diesel engine noise to establish objective criteria for sound quality assessment. Considering the sensitivity of human hearing to impulsive sounds such as diesel noise, the human auditory mechanism was simulated by introducing temporal masking in the time domain. Furthermore, each of the human auditory organs was simulated by computer codes, providing reasonable analytical explanations of typical human hearing responses to diesel noise. This method finally provides the sound quality index of vehicle diesel engine noise that includes high frequency intermittent offensive sounds caused by impacting excitations of combustion and piston slap.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.593-601
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• 2006

In many fire emergencies, the auditory fire alarm signals are very important to save the occupant's life. But as the sound insulation of building elements has been improved, it is more difficult for occupant to recognize the fire alarm signals when the audible fire alarm worked. This is the first study to show the sound attenuation of audible fire alarm device in apartments. We measured and analyzed the sound attenuation level in seven units. The result showed that it was not sufficient to detect the sound from the fire alarm device in bedrooms. Whether the fire alarm device worked or not, the differences of sound level in bedrooms were below 1$\sim$10 dBA. To give the minimum sound level 60 dBA in bedrooms, the proper sound levels from alarm device installed in livingrooms were suggested using computer simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.580-586
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• 2005

In this study, experimental tests for driving noise of various optical disk drives (ODD) have been performed using 1/2' microphone noise measurement system. Several new and old ODD models by different manufacturers are practically considered and compared far realistic driving conditions. Sound insulation case with absorbing material fur the present experimental tests is designed and constructed using CATIA system. It is found that average data transfer rate, operating RPM, and sound noise level seems to be different for the same opposed speed ODD by different manufacturers. Moreover, driving sound noise level can be largely affected by both tray shape and driving speed even for the same apparent data transfer rate.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.94-99
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• 2017

Breaking the rigid connection between the two faces of the wall can significantly improve the sound transmission loss of the wall. This is usually achieved by resiliently mounting the gypsum board on one of the two faces of the wall using resilient channel. Resilient channel with less stiffness than that of air cavity could move the resonance frequency of the light-weight wall. So we can get higher sound transmission loss at low frequencies for light-weight wall using resilient channel. It's sound transmission loss is 17 dB higher than that of single stud wall, and 5 dB higher than that of double stud wall.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.10 s.103
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• pp.1169-1176
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• 2005

In this study, experimental tests for driving noise of various optical disk drives (ODD) have been performed using 1/2' microphone noise measurement system. Several new and old ODD models by different manufacturers are practically considered and compared for realistic driving conditions. Sound insulation case with absorbing material for the present experimental tests is designed and constructed using CATIA system. It is found that average data transfer rate, operating RPM, and sound noise level seem to be different for the ODD models with same denoted speed by different manufacturers. Moreover, driving sound noise level can be largely affected by both tray shape and driving speed even for the condition of the same apparent data transfer rate.

• Journal of KSNVE
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• v.10 no.4
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• pp.662-668
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• 2000

Sound transmission characteristics are investigated on the aluminium extruded panels used for railway vehicles. An equivalent orthotropic plate model and mass law are applied to predict the sound transmission loss. An extruded panel specimen used in the floor of railway vehicles is manufactured and is tested to measure sound transmission loss by two reverberant chamber method. Predicted transmission loss I compared with measured values and the effect of local resonance on the transmission characteristics is identified. The results are applied to design the extruded panel having better sound insulation performance.

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.41-52
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• 2011

This study was carried out to investigate the effect of energy saving and sound insulation of building materials mixed with charcoal. To investigate the functionality of building based on the difference of construction materials, three different experimental buildings were constructed. They were buildings built with the conventional construction materials (A), the charcoal construction materials (B), and the charcoal-sericite construction materials (C). The study showed that energy consumption could be reduced approximately 9.5% and 14.5% by replacing A with B and C, respectively. Especially, it is revealed that the lower outdoor temperature was, the higher energy saving effect was. Also, after shutoff the boiler switch the decrease rate of room temperature of the one using B was lower than those of others using A and C so that the room temperature at the building using B was higher by $3.5{\sim}4.2^{\circ}C$ in the 1 meter air above the ground and by $4.4{\sim}5.4^{\circ}C$ on the floor surface after 12 hours passed. In the building noise test the heavy-and light-weight impact sound of the plate, represented by criterion of noise between floors in multi-story building, tended to decrease in the test sample containing charcoal.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.592-597
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• 2013

It is widely known that the sound insulation of soundproof panel is highly correlated to two factors, surface density of material and the frequency of noise. Accordingly, the character of traffic noise released in actual situation is important requisite for determining thickness to determine surface density and material of soundproof panel. This present study selected polymer panel with advantage of light weight and workability and evaluates according to frequency of traffic noise. Polypropylene (PP) and high-density polyethylene (HDPE) were selected as subjects based on economic valuation and efficiency. The sound transmission loss of selected polymer panels were compared with the currently used panels such as polycarbonate (PC) and polymethyl methacrylate (PMMA) depending on thickness and materials. As a result, PC showed the highest sound transmission loss followed by PMMA, HDPE, and PP in range of mass law. In terms of acoustic performance on thickness, the transmission loss increased with thickness of soundproof panel meanwhile coincidence dip was observed in lower frequency where had reduced transmission loss. Therefore, it is suggested that after determining target frequency, the kind of materials and thickness of soundproof panel need to be designed so that traffic noise can be more efficiently reduced.

• The Journal of the Acoustical Society of Korea
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• v.9 no.2
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• pp.42-52
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• 1990

A method of measuring impulse response of acoustic system, two kinds of cross-correlation methods (the direct correlation method and the M-sequence modulation correlation method) were applied. According to the direct correlation method, by using stationary random noise source and by calculating the cross-correlation function between the sourece and the output signal, equivalent impulse response can be obtained not being influenced by the back ground noises. By applying this method, the measurement of echo-time patterns in rooms and oblique incident sound absorption characteristics of sound absorbing materials was carried out. In the case of the M-sequence modulation correlation method which was contrived by Aoshima, an intermittent random nosie modulated by M-sequence signal is used as the source signal, and the cross-correlation function between the M-sequence signal and the squared output signal is calculated. According to this method, equivalent energy impulse response (squared impulse response) of te propagation system can be obtained without being influenced by the back ground noises and the air fluctuation caused by wind. As the applcaition of this measuring method to the architectural acoustics, the meaurements of echo-time patterns, reverberation decays and sound pressure lev디 distributions in rooms and sound insulation efficiencies in buildings were carried out. From these experimental studies, it has been found that this M-sequence modulation correlation method is markedly useful especially for the field masurement of sound insulation under high back ground noise condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.414-422
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• 2013

As structure-borne sound, the floor impact sound is one of the serious noises in residential building. Most of heating system applied to the typical Korean residential building is floor heating system which is called ondol. The ondol usually consists of finishing material, mortar with heating coil, light-weight aerated concrete and reinforced concrete. This study focused on the isolation of heavy-weight impact sound and modification of mortar and light-weight aerated concrete. Specifically the glass foam aggregate was added on light-weight aerated concrete. Also, water-cement ratio and amount of cement on mortar were revised. The sound pressure level of heavy-weight impact was measured in reverberation chamber using both bang-machine and impact ball. The size of specimen was 1 m by 1 m. Substitution ratio of glass foam aggregate on light-weight aerated concrete shows relationship with heavy-weight impact sound pressure level. In addition, heavy-weight impact sound pressure level was decreased with increment of water-cement ratio and amount of cement on mortar.