• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1142-1146
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• 2007

In this studies, subjective evaluation of heavy-weight floor impact sound through classification was conducted. Heavyweight impact sounds generated by an impact ball were recorded through dummy heads in apartment buildings. The recordings were classified according to the frequency characteristics of the floor impact sounds which are influenced by the floor structure with different boundary conditions and composite materials. The characteristics of the floor impact noise were investigated by paired comparison tests and semantic differential tests. Sound sources for auditory experiment were selected based on the actual noise levels with perceptual level differences. The results showed that roughness and fluctuation strength as well as loudness of the heavy-weight impact noise had a major effect on annoyance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1865-1870
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• 2000

Sound propagation along the surface of the ground can be affected by the roughness of the ground surface and the direction of the wind. Noise Source parameter and ground factor are estimated using the measured results of two points under particular environmental condition, and the noise level of arbitrary points under the same environmental condition can be estimated. The results can be used for the prediction of the noise level from a source above a plain and homogeneous ground surface with no obstacles nearby. Upward and downward conditions are also addressed in addition to ground effect. The proposed method can be utilized to estimate the noise level of specific noise environment and its validity was confirmed with the results of actual field measurement.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.17-20
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• 2008

An Electric motor is used for user-friendly equipment in vehicles. In this paper, an electric motor for windows is considered for the tunning of engineering inspection concerned with noise level from it. Noise from the electric window motor is a kind of structure-borne noise and becomes a reference parameter for its engineering performance. Estimation of noise from the motors shows the quantitative values such as overall noise. Noise level at each frequency and the qualitative figures for the transient characteristics of sound are also revealed. The loudness level, one of the qualitative parameters, distinguishes the performances of every components by the comparison of its magnitude. In summary, it is found that the qualitative comparisons become useful means for the inspection of electric motors.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.121-129
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• 2016

The noise pattern of a household refrigerator is dependent on the characteristics of its operating cycle which is repeated with a specific pattern depending on various parameters, such as room temperature and performance of its mechanical parts. Analysis of noise pattern is essential prior to evaluation of sound quality of a refrigerator. In this study, 14 units of refrigerator were classified into 4 types according to noise pattern and sort of mechanical part, which helps to analyze characteristics of refrigerator noise. Sound quality metrics(loudness, sharpness, roughness, and fluctuation strength) were calculated to compare noise pattern of the 4 types of refrigerator. The results of this study can be useful to decide noise performance of refrigerator.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.51-53
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• 2005

Considerable noise is sometimes associated with degeneration of the hee joint surface. Such noise may indicate roughness or softening of the cartilage surfaces, and may be a useful index for early disease. In this study, we have evaluated arthritic pathology using the acoustical analysis of knee joint sounds. During sitting and standing periods, subjects' active knee flexion and extension were monitored. Fundamental frequency, mean amplitude of pitch, jitter and shimmer were analyzed according to the position and the joint angle. The result showed that the fundamental frequency of the 2nd patient group and standing position was higher than the others, and that the pitch of sounds changed unstably. These results suggest that an analysis of knee joint sound might assist non-invasive diagnosis of an articular pathology.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.242-247
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• 2018

The automotive industry is making various efforts to cope with ever-increasing exhaust emissions and fuel economy regulations. However, this often results in degraded NVH (Noise, Vibration, and Harshness) performance. For example, we proposed the causes and improvements for the noise generated by the high-pressure pump noise of a gasoline engine, the change of acceleration noise due to dual injection of MPI (Multi-Point Injection) and GDI (Gasoline Direct Injection), the noise of a gasoline turbocharger, and the combustion noise deteriorated due to the injection parameters calibration in a diesel engine. Since these noises are caused by the high frequency noise, and the driver feels the rough sound quality, efforts to reduce them with proper NVH measures are indispensable.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.283-286
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• 1998

monaural 신호는 귀의 특성과 인간의 청취 특성을 정확하게 반영하지 못하는 문제점이 있다. 귀 자체의 특성이 binaural인 것을 생각하면 monaural 신호를 이용한 방법은 정확한 결과가 나오기 어렵다. 따라서 이 논문에서는 monaural 신호를 이용한 음질 평가 시스템의 단점을 보완하고 귀의 binaural 특성을 살린 binaural 음질 평가 시스템을 구현하였다. 소리에 대한 심리음향학 인자로는 monaural 평가에서 사용했던 loudness, sharpness, roughness, fluctuation strength, annoyance, pleasantness를 binaural에 맞도록 수정하였으며, monaural 평가에서는 사용하지 않았던 tonality를 추가하여 pleasantness의 annoyance의 계산식을 수정하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.85-88
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• 1998

심리음향학적으로 소리의 감성 요소를 평가하려는 시도가 계속되고 있으나 뚜렷한 결과가 나온 것은 많지 않다. 또한 감성 인자 평가에 대한 국제적인 표준도 정확히 나와있지 않다. 일반적으로 심리음향학 인자로 loudness, sharpness, roughness, fluctuation strength, pleasantness, annoyance를 사용하며, 이러한 인자들을 이용하여 바이노럴 음질 평가 시스템을 구현하였다. 구현된 바이노럴 음질 평가 시스템의 객관성을 평가하기 위해 인성 실험을 실시하였고 인성 실험 결과와 음질 평가 시스템을 이용한 평가 결과를 비교 분석하였다.

• Fashion & Textile Research Journal
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• v.14 no.4
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• pp.641-647
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• 2012

This study investigates the sound properties of fabric frictional sound (SPL, ${\Delta}L$, ${\Delta}f$) according to the film type of PTFE laminated vapor-permeable water-repellent fabrics in order to understand the relationship between SPL and the basic properties of fabrics such as layer, yarn type, and thickness of fiber. This study accesses their mechanical properties and determines how to control them to minimize SPL. Eight PTFE laminated water-repellent fabrics, composed of four different film types (A, B, C, D) and with two different fabrics, were used as test specimens. Frictional sounds generated at 1.21m/s were recorded by using a fabric sound generator and SPLs were analyzed through Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured by KES-FB. The SPL value was lowest at 74.4dB in film type A and highest as 85.5dB in type D. Based on ANOVA and post-hoc test, specimens were classified into less Loud Group (A, B) and Loud Group (C, D). It was shown that SPL was lower when 2 layer (instead of 3 layer), filament yarn than staple, and thin fiber than thick were used. In Group I, shearing properties (G, 2HG5), geometrical roughness (SMD), compressional properties (LC, RC) and weight (W) showed high correlation with SPL however, elongation (EM) and shear stiffness (G) did with SPL in Group II.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.897-903
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• 2006

The reduction of the vehicle interior noise has been the main interest of noise and vibration harshness (NVH) engineers. The driver's perception on the vehicle noise is affected largely by psychoacoustic characteristic of the noise as well as the SPL. In particular, the heating, ventilation and air conditioning (HVAC) system sound among the vehicle interior noise has been reflected sensitively in psychoacoustics view point. Even though the HVAC noise is not louder than overall noise level, it clearly affects subjective perception to drivers in the way of making to be nervous or annoyed. Therefore, these days a vehicle engineer takes aim at developing sound quality as well as reduction of noise. In this paper, we acquired noises in the HVAC from many vehicles. Through the objective and subjective sound quality (SQ) evaluation with acquiring noises recorded by the vehicle HVAC system, the simple and multiple regression models were obtained for the subjective evaluation 'Pleasant' using the semantic differential method (SDM). The regression procedure also allows you to produce diagnostic statistics to evaluate the regression estimates including appropriation and accuracy. Furthermore, the neural network (NN) model were obtained using three inputs(loudness, sharpness and roughness) of the SQ metrics and one output(subjective 'Pleasant'). Because human's perception is very complex and hard to estimate their pattern, we used NN model. The estimated models were compared with correlations between output indexes of SQ and hearing test results for verification data 'Pleasant'. As a result of application of the SQ indexes, the NN model was shown with the largest correlation of SQ indexes and we found possibilities to predict the SQ metrics.