• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.66-75
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• 1997

Sound transmission from the luggage comparment into the car cabin is important in the viewpoint if exhaust and road noises of passenger cars. In this paper, acoustic modal coupling between passenger and luggage compartments through loudspeaker holes at parcel shelf is dealt with for a sedan type passenger car with rigid rear seat. For these purposes, a half-scaled model car is tested and computed by the indirect BEM. Predicted acoustic transfer functions are compared with experimental ones and they agree reasonably well. It is found that the fore-aft resonance frequencies of the passenger cavity in the absence of coupling holes are tend to shift to higher frequencies when the luggage compartment is coupled to the passenger cavity.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2E
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• pp.65-72
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• 1995

An algorithm for evaluating the subjective performance of a loudspeaker is proposed based on the frequency response characteristic. Objective ratings using the proposed algorithm were compared with the results of the listening test. It was verified that the ratings of the proposed algorithm showed a good correspondence with the results of the listening test.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.93-98
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• 1998

Magnetic fluids have been used in the commercial area, e. g damping, sealing and hydrodynamic bearing. In this study, magnetic fluid was made for damping in loudspeaker. The magnetic fluids were snthesized by dispersing the magnetite powder which was obtained by precipitation method in Yubase oil. When the magnetic fluid was applied to a 6 cm tweeter, improvements of damping, centering and heat transger in a loudspeaker were noted. Also we compared the performance of the magnetic fluid with 20 % magnetite in the oil and the one of APG-815 (Niphon Ferrofluidic Co.)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.645-651
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• 2003

The system in which a microphone and a loudspeaker are simultaneously used can cause an echo. The echo is caused by feedback between the output of the loudspeaker and the input of the microphone. The acoustic echo canceller is a device to cancel the echo in a communication system. Its general procedure for cancellation is first estimating the plant response of the feedback path and then eliminating the feedback signal from the input signal. In this paper, full-band and sub-band approaches are compared by using some simulation examples.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.84-86
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• 2015

본 논문에서는 2차원으로 배열된 4개의 스피커를 이용한 음향 재생환경에서 청취자의 위치에 따라 최적의 sweet spot을 제공하도록 스피커를 구동하는 방법을 제안한다. 먼저 청취자의 위치를 추적하여 청취자의 귀와 스피커 쌍 후보 사이의 경로의 비율을 구한다. 다음, 청취자의 위치를 고려하여 스피커 쌍 후보들의 스피커 간 거리 비율을 구한다. 마지막으로, 앞서 구한 두 개 거리 비율의 비율이 1에 가까운 스피커 쌍을 구동 스피커로 결정하고 cross-talk cancellation을 음원에 적용하여 청취자에게 제공한다. 모의실험을 통해, 청취자의 위치가 변할 때 제안하는 스피커 구동 방법을 사용하여 기존의 방법보다 청취자에게 넓은 sweet spot을 제공할 수 있음을 확인하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.1058-1063
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• 1994

In this study we developed monosyllable lists for articulation test for Korean. We sampled 103,581 colloquial monosyllables, applied them to five selection rules that based on Korean linguistic characteristics, and finally constructed five different lists with fifty monosyllables. The validity test using the monaural impairment factors such as S/N ratio and cut-off frequency showed that articulation scores were chanted systematically according to the level of impairment factors. In addition, we investigated the effect of azimuth of a single competing sound upon articulation scores. The syllables were always reproduced by the loudspeaker in front of the subject, while Hoth noise were reproduced by the loudspeaker with varying azimuth around subject. The result indicated that the articulation depended on the azimuth of competing sound sources. Finally, no significant differences among lists were found in all experimental conditions.

• 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.

• Textile Coloration and Finishing
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• v.28 no.1
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• pp.40-47
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• 2016

As a coating material for loudspeaker dampers, resilient polyurethane/epoxy hybrid resins were synthesized to replace conventional phenol resin and examined the physical properties, which are not only environmentally friendly but also not harmful to human. Five types of polyurethane resins were synthesized in the step-shot method using methylene diisocyanate, three polyols such as poly tetramethylene ether glycol(PTMEG, MW:2000), poly(1,4-buthylene adipate(PBAP, MW:2000), and poly carbonatediol(PCD, MW:2000), and three chain extenders such as ethylene glycol(EG), neopentyl glycol(NPG), and 1,4-buthandiol(1,4-BD). The five types of synthesized polyurethane resins and commercially available bisphenol A type epoxy resin were blended in weight ratios of 90:10, 70:30, and 50:50 to synthesize 15 types of polyurethane/epoxy hybrid resins. Among the polyurethane resins, the one that was synthesized using PCD and 1,4-BD showed excellent tensile strength, 100% modulus, low extension, and relatively high viscosity. Polyurethane/epoxy hybrid resins with higher epoxy resin contents showed better thermal properties and water resistance while those with higher polyurethane contents showed higher flexibility. The polyurethane/epoxy hybrid resin made by blending the polyurethane based on PCD and 1,4-BD with a bisphenol A type epoxy resin in a weight ratio of 70:30 was identified to be the most suitable to be used in speaker dampers.

• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.66-76
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• 2000

Acoustic performance of loudspeakers for sound reproduction has been qualitatively evaluated by using the listening test by juries in the development and final evaluation stages. However, the subjective evaluation method has many problems in the viewpoint of reliability and repeatability that are mainly related to the jury performance, as well as time and economy. In this reason, objective techniques should be tried to evaluate the acoustic performance of loudspeakers as well as the conventional subjective test. The object of this study is to find if there is any correlation between the statistically treated in test results and the measured results based on the loudness of reproduced sound signals. For the four-step statistical analysis, the analysis of variance (ANOVA) and Tukeys method are employed for dealing with the data from the listening test. For the objective evaluation, Zwickers loudness considering the human hearing characteristics is calculated for the measured sound signal emitted from each loudspeaker and the objective ratings such as fidelity rating (FR) and softness rating (SR) is suggested. The correlation between two ratings has been demonstrated for an actual set of loudspeakers using FR, SR and correlation coefficient. The method in this study can be useful in statistically evaluating commercial or prototype loudspeakers without using very time-consuming and expensive subjective testing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.866-867
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• 2009