• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.1162-1168
• /
• 2007

In many fire emergencies, the audible 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 fire alarm worked. This is the study to show the sound attenuation of the fire alarm sounder system in apartment buildings. We measured and analyzed the sound attenuation level in 17 units, and the results were compared with the minimum sound level at sleeping area by NFPA(National Fire Protection Association) 72. When only the fire alarm worked in stair hall, the sound levels in bedroom were in the range of $30.6{\sim}42.8dB(A)$ and the differences between sound level and ambient sound level in bedrooms were in the range of $7.1{\sim}13.8dB(A)$. And when the emergency broadcasting device in the livingroom and the fire alarm worked simultaneously, the sound levels in bedrooms were in the range of $54.2{\sim}63.0dBA$. Finally, it was showed that the fire alarm sounder system didn't give a sufficient sound level in bedroom to awake out of sleep.

• Tribology and Lubricants
• /
• 제19권1호
• /
• pp.15-20
• /
• 2003

The purpose of the paper is to investigate the effects of design parameters on the noise of a rotor- bearing system supported in oil lubricated journal bearings. Effects of radial clearance and width of the bearing, lubricant viscosity and mass eccentricity of the rotor are also examined. Numerical results of the parametric studies are summarized through graph for the A-weighted sound pressure level of the bearing with respect to the rotational speed of the rotor. Results show that the sound pressure level of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing. The high viscosity of the lubricant slightly decreases the noise of the bearing, but its effect is relatively very low at high speed. The results of the paper could be an aid in the low noise design of rotor-bearing system supported in oil lubricated journal bearings.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제4권4호
• /
• pp.374-385
• /
• 2012

The indoor noise of a ship is usually determined using the A-weighted sound pressure level. However, in order to better understand this phenomenon, evaluation parameters that more accurately reflect the human sense of hearing are required. To find the level of the satisfaction index of the noise inside a naval vessel such as "Loudness" and "Annoyance", psycho-acoustic evaluation of various sound recordings from the naval vessel was performed in a laboratory. The objective of this paper is to develop a single index of "Loudness" and "Annoyance" for noise inside a naval vessel according to a psycho-acoustic evaluation by using psychological responses such as Noise Rating (NR), Noise Criterion (NC), Room Criterion (RC), Preferred Speech Interference Level (PSIL) and loudness level. Additionally, in order to determine a single index of satisfaction for noise such as "Loudness" and "Annoyance", with respect to a human's sense of hearing, a back-propagation neural network is applied.

• 대한교통학회지
• /
• 제5권2호
• /
• pp.73-80
• /
• 1987

Various procedures for evaluation of traffic noise annoyance have been proposed. However, most of the studies of this type are restricted for improving traffic flow. In this paper, a method to predict the road traffic noise is proposed in terms of equivalent continuous A-Weighted sound pressure level (Leq), based on a probability model. First, distribution of the road traffic noise level are investigated. second, the weibull distribution parameters are estimated by using the quantification theory. Finally, a prediction model of the road traffic noise is proposed based on the weibull distribution model The predicted values of the Leq are closely matched the measured data.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.435-438
• /
• 2005

Until now, a home appliance mostly has revealed physical quantities created by the standpoint of engineers, by using the A-weighted sound pressure level and the sound power. It is, however, obviously impossible to characterize a complex sound with a single number. Many parameters must be considered. In addition to loudness, we must take into account frequency and amplitude variation over time, spectral balance, tonality, and many other attributes. Thus, in this research, the general tendency of consumer psychology was investigated for the refrigerator's sound. The noise from the refrigerator was evaluated by not only the simple sound pressure levels but also the consumer's sense of hearing. And also, in order to improve the quality of sound through the design change, the consumer's evaluation was analysed and related to the engineering quantities. With the several design changes, finally the most silence refrigerator in the world was developed with considering the consumer's hearing of sense.

• 한국도로학회논문집
• /
• 제16권5호
• /
• pp.59-66
• /
• 2014

PURPOSES : This study is to predict the Sound Pressure Level(SPL) obtained from the Noble Close ProXimity(NCPX) method by using the Extended Kalman Filter Algorithm employing the taylor series and Linear Regression Analysis based on the least square method. The objective of utilizing EKF Algorithm is to consider stochastically the effect of error because the Regression analysis is not the method for the statical approach. METHODS : For measuring the friction noise between the surface and vehicle's tire, NCPX method was used. With NCPX method, SPL can be obtained using the frequency analysis such as Discrete Fourier Transform(DFT), Fast Fourier Transform(FFT) and Constant Percentage Bandwidth(CPB) Analysis. In this research, CPB analysis was only conducted for deriving A-weighted SPL from the sound power level in terms of frequencies. EKF Algorithm and Regression analysis were performed for estimating the SPL regarding the vehicle velocities. RESULTS : The study has shown that the results related to the coefficient of determination and RMSE from EKF Algorithm have been improved by comparing to Regression analysis. CONCLUSIONS : The more the vehicle is fast, the more the SPL must be high. But in the results of EKF Algorithm, SPLs are irregular. The reason of that is the EKF algorithm can be reflected by the error covariance from the measurements.

• 대한조선학회논문집
• /
• 제47권4호
• /
• pp.589-597
• /
• 2010

The indoor noise of the naval vessel is very important considering hearing protection, improvement of working environment and easily communication between crews. When the environment of the naval vessel suffering from the noise is considered, it is very important to be quiet in the living area where the crews have a rest sufficiently. In addition, the noise of the working area should be reduced in order to increase working efficiency. Therefore, in this research, the satisfactions about the indoor noise are survey for crews working in a naval vessel. Through this survey, the relationship between the indoor noise and crew's satisfaction about it can be found. As a result, the limit of sound pressure level which almost all crew can be satisfied with the indoor noise about their living and working area is suggested base on the survey in this research.

• 한국음향학회지
• /
• 제25권3호
• /
• pp.129-136
• /
• 2006

소음에 대한 인간의 심리적 인지는 소음의 여러 가지 물리적 요인에 의하여 영향을 받는다. 그러나 현재의 환경소음 평가는 A 가중치 등가 소음 수준을 기준으로 평가되고 있으며 인간의 다양한 감성적 요인을 반영하지 못하고 있다. 따라서 본 연구에서는 환경소음 평가를 위하여 환경소음원 43개에 대하여 주관평가와 통계적 분석방법을 사용하여 인간의 감성에 영향을 주는 음질인자 (Sound quality factor)를 분석하였다. 분석방법은 먼저 다양한 환경소음원에 대한 음질물리량 (Sound quality metrics)을 분석하여 음원을 분류하였으며 분류된 음원의 주된 음질 물리량을 고찰하였다. 그리고 쌍대비교법 (Paired comparisons method)과 어의분별척도법 (Semantic differential method)을 사용하여 주관 평가를 실시하고 음질의 요인을 분석하였으며 물리량과의 관계를 규명하였다. 마지막으로 요인에 대한 물리량의 기여도를 분석함으로써 환경소음의 감성적 인지에 대한 기초 물리량을 설정하였다.

• 한국소음진동공학회논문집
• /
• 제21권7호
• /
• pp.650-656
• /
• 2011

The noise inside a naval vessel is very important in considering the need for hearing protection, improving the working environment and maintaining good communications for crews living on board a naval vessel. The indoor noise of a ship usually is specified by the A-weighted sound pressure level, but other evaluating parameters are required to reflect human senses more effectively. This paper uses additional noise indices related to room acoustics, such as NR(noise rating), NC(noise criterion), RC(room criterion), PSIL(preferred speech interference level) and loudness level to evaluate the noise inside cabins on a naval vessel. Using these psychological noise indices, allowable limit of noise level in cabins is suggested through psycho-acoustic evaluation for the noise in cabins.

• 한국음향학회지
• /
• 제8권5호
• /
• pp.51-58
• /
• 1989

유한요소법은 일반적으로 변분원리를 이용해 정식화를 하고 있으나, 본 연구에서는 웨이티드 잔차법으로 아주 좋은 근사해를 얻을 수 있다는 Galerkin법에 의해 Helmholtz방정식으로부터 직접 유산요소 정식화하는 방법을 소개하고, 정식화한 수치계산법을 2, 3차원 음장의 고유모드 및 음향방사상태해석에 응용하였다. 또한 수치 계산결과를 확인하기 위하여 간단한 모형을 제작, 실내음향 모드와 음압분포 등의 측정도 병행하였으며 그 결과, 유한요소법에 의한 수치해석결과의 측정치가 잘 맞는 것을 알았다.