• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.445-451
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• 2003

Booming sound is one of the most important interior sound of a passenger car. The conventional booming noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level cannot give the whole story about the booming sound of a passenger car. In this paper, we employed sound metrics, which are the subjective parameters, used in psycoacoustics. According to recent research results. the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for booming sound of a passenger car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.997-1002
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• 2004

Rumbling sound is one of the most important interior sound of a passenger car. The conventional rumbling noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level can not give the whole story about the rumbling sound of a passenger car. In this paper, we employed sound metric which is the subjective parameter used in psycoacoustics. According to recent research results, the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for rumbling sound of a passenger car.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.3
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• pp.197-205
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• 2004

In this paper, we studied on the hardware implementation of a 3${\times}$3 window weighted median filter using bit-level sorting algorithm. The weighted median filter is a generalization of the median filter that is able to preserve :,harp changes in signal and is very effective in removing impulse noise. It has been successfully applied in various areas such as digital signal and video/image processing. The weighted median filters are, for the most part, based on word-level sorting methods, which have more hardware and time complexity, However, the proposed bit-serial sorting algorithm uses weighted adder tree to overcome those disadvantages. It also offers a simple pipelined filter architecture that is highly regular with repeated modules and is very suitable for weighted median filtering. The algorithm was implemented by VHDL and graphical environment in MAX＋PlusII of ALTERA. The simulation results indicate that the proposed design method is more efficient than the traditional ones.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.327-333
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• 2021

Magnetic resonance imaging(MRI) uses strong magnetic field to image the cross-section of human body and has excellent image quality with no risk of radiation exposure. Because of above-mentioned advantages, MRI has been widely used in clinical fields. However, the noise generated in MRI degrades the quality of medical images and has a negative effect on quick and accurate diagnosis. In particular, examining a object with a detailed structure such as brain, image quality degradation becomes a problem for diagnosis. Therefore, in this study, we acquired T2 weighted 3D data of multiple sclerosis disease using BrainWeb simulation program, and used quantitative evaluation factors to find appropriate slice thickness among 1, 3, 5, and 7 mm. Coefficient of variation and contrast to noise ratio were calculated to evaluate the noise level, and root mean square error and peak signal to noise ratio were used to evaluate the similarity with the reference image. As a result, the noise level decreased as the slice thickness increased, while the similarity decreased after 5 mm. In conclusion, as the slice thickness increases, the noise is reduced and the image quality is improved. However, since the edge signal is lost due to overlapped signal, it is considered that selecting appropriate slice thickness is necessary.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1122-1127
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• 2003

For many years, engineers in the field of acoustics have used the A-weighted sound pressure level (SPL). Since they were interested just in a reduction of noise, the A-weighted SPL was considered good enough to quantify noise problems. This is reasonable because loudness is usually the most important parameter for most noise problems and A-weighted SPL is often reasonably well correlated with loudness. As the overall noise levels drop, however, other parameters become more important and must be considered, Advent of sound quality came from an understanding that A-weighted SPL only reflects the loudness of a sound. It is obviously impossible to characterize a complex sound with a single number. Although product mostly has revealed physical quantities created by the standpoint of engineers, consumers perceive and evaluate products on the non-physical characteristics, such as feelings, emotions, and experiences in different social and cultural situations. Especially, for the household appliances for instance air-conditioner or refrigerator, the sound is heavily related to the satisfaction of a customer who is a real user of the product and is very important factor to decide purchasing as well as visual design. Therefore, in this research, the general tendency of consumer's psychology was investigated for the appliances. And also, in order to obtain clear guidelines fur sound manipulation, the characteristics of the sound of air-conditioning systems and refrigerators were compared with competitors'. since it is important to overcome the discrepancy between engineering and marketing, the relevance of sound manipulation must be documented from the consumer's perspective. That is the reason why we conducted a consumer and marketing oriented study.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.189-199
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• 1999

The revision was proposed for methods A-weighted sound pressure measurement for fans, blowers and compressors in order to apply newly developed measurement techniques to KS B 6361 established in 1987. This proposal includes modification of terminologies, revision of sound power methods for radiated sound from the body, inclusion of In-duct measurement method, and correction method for flow noise upon microphon.

• Journal of KSNVE
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• v.10 no.5
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• pp.792-799
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• 2000

Aircraft noise in the vicinity of Kimpo international airport has damaged to large number of people who live in communities. This paper investigates noise exposed area due to aircraft flight based on prediction modeling program INM and flight path data. Especially effect on route for aircraft has been considered. Ti also examines noise impact for various flight modes, such as a thrust cutback climb method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.291-294
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• 2005

In this study, we compared and analyzed the floor impact sound insulation performance produced by the rating methods. The rating methods are using reversed A-weighting curve, A-weighted sound pressure levels and arithmetic average. On-site floor impact sound pressure levels of living room and room are measured. The results of this study are 1)the rating using reversed A-weighting curve for heavy-weight impact sound's standard deviation is lower than that of light-weight impact sound, 2)the number of rating using A-weighted sound pressure levels and arithmetic average is larger than that of using reversed A-weighting curve, and 3)the number of rating using reversed A-weighting curve mainly depends on impact sound pressure level of 63Hz in heavy-weight impact sound.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.612-615
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• 2006

In this study, we compared and analyzed the floor impact noise insulation performance produced by the rating methods. The rating methods are using reversed A-weighting curve, A-weighted sound pressure levels(dB(A)). The results of this study are(1)dB(A) by the specified frequency is 0.5dB(A) at light weight and 2.5dB(A) at heavy weight upper than all pass dB(A)(2)the rating using reversed A-weighting curve is 5dB lower than dB(A)(3)the number of rating using reversed A-weighting curve mainly depends on impact noise pressure level of 63Hz in heavy weight but dB(A) does not.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.107-114
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• 2004

This paper presents block and timing diagrams of the DWA(Data Weighted Averaging) to optimize a feedback time delay of the sigma-delta modulator. Through the MATLAB modeling, the optimized coefficients of the integrators are obtained to design the modulator. The fully differential SC integrators, feedback DAC, 9-level quantizer, and DWA are designed by considering the nonideal characteristics of the modulator. The designed third-order multibit modulator is fabricated in a 0.35${\mu}{\textrm}{m}$ CMOS process. The modulator achieves 75dB signal-to-noise ratio and 74dB dynamic range at 1.2Vp-p 825kHz input signal and 52.8MHE sampling frequency.