• Journal of Preventive Medicine and Public Health
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• v.26 no.4 s.44
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• pp.565-573
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• 1993

Noise is not only affecting the ear and the auditory cortex locally, but its influence is widely spread throughout the brain structures, e. g., the reticular formation, the brain stem nuclei or the subcortical forebrain area. Hence, any of the organism's activities can be hindered or stimulated by noise. High noise is a stressor and the catecholamine level can be used both as a stress marker and as an indicator of modified sympathetic nervous system activity. Several recent studies have found that the urinary excretion of catecholamines is increased due to high noise intensity, especially unexpectedly high and long lasting noise. The present study was conducted in order to examine the effects of noise stress on urinary excretion of ctecholamines in rats and humans. Rats were exposed to 90 dB noise for 10, 30, and 60 minutes, 3 and 12 hours. 24 hour . urinary samples were collected and the catecholamones were extracted by alumina and analyzed by HPLC-ECD. Catecholamine levels increased with time of exposure up to 60 minutes : norepinephrine concentration at 60 min of noise=1.038 ng/ml, epinephrine=0.636 ng/ml. Urine catecholamines of blue collar workers exposed to 90 dB of noise at the work place were collected between 2 and 4 p.m. and compared to that of white collar workers exposed to 70 dB. Mean norepinephrine level of the blue collar workers was 0.89 ng/ml (${\pm}0.25$), epinephrine 0.24ng/m1 (${\pm}0.09$), and that of the white collar workers 0.48 ng/ml (${\pm}0.12$), epinephrine 0.19 ng/ml(${\pm}0.05$). It was concluded that noise acts as a stressor and increases the catecholamine levels in both rats and humans.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.818-827
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• 2008

In this paper, we propose a new noise estimation and reduction algorithm for stationary and nonstationary noisy environments. This approach uses an algorithm that classifies the speech and noise signal contributions in time-frequency bins. It relies on the ratio of the normalized standard deviation of the noisy power spectrum in time-frequency bins to its average. If the ratio is greater than an adaptive estimator, speech is considered to be present. The propose method uses an auto control parameter for an adaptive estimator to work well in highly nonstationary noisy environments. The auto control parameter is controlled by a linear function using a posteriori signal to noise ratio(SNR) according to the increase or the decrease of the noise level. The estimated clean speech power spectrum is obtained by a modified gain function and the updated noisy power spectrum of the time-frequency bin. This new algorithm has the advantages of much more simplicity and light computational load for estimating the stationary and nonstationary noise environments. The proposed algorithm is superior to conventional methods. To evaluate the algorithm's performance, we test it using the NOIZEUS database, and use the segment signal-to-noise ratio(SNR) and ITU-T P.835 as evaluation criteria.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.255-257
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• 2018

Recently, as the frequency of use of video media increases in various fields, the importance of signal processing is increasing. However, many kinds of noise are generated in the transmission and reception process and affect the information of the signal. For this reason, the noise removal is essential as a preprocessing process. In this paper, we propose an algorithm to remove mixed noise of impulse noise and AWGN. The proposed algorithm restores the image through noise determination and pixel change for efficient noise removal. Unlike the conventional method, noise is removed by minimizing both noise effects. Simulation showed excellent noise removal characteristic results were compared and analyzed using the PSNR for such decisions.

• Journal of the Korean Society of Clothing and Textiles
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• v.47 no.1
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• pp.110-122
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• 2023

The COVID-19 pandemic increased people's time at home and caused an 80% increase in noise disputes between floors. The purpose of this study is to propose suitable materials for making indoor shoes (insoles) to minimize noise between floors. Subjects without back pain and leg-related disease (e.g. arthritis, etc.) from three different age groups (childhood, adolescence, and adulthood) were recruited for the study. Five polymer insole materials were considered: Chloroprene Rubber (CR foam), Ethylene Propylene Diene Monomer (EPDM foam), Natural Latex foam, Ethylene Vinyl Acetate (EVA foam), and Polyurethane (PU foam). From these materials, 20 combinations were prepared and randomly tested for noise and vibration. The results revealed a significant difference in noise and vibration levels based on the type of material used and the age of the subject. Nevertheless, all materials under consideration successfully reduced noise and vibration; in particular, type A-C greatly decreased. The CR foam material was especially effective at noise and vibration reduction (p<.01). This study suggests that adding insoles into socks that children wear at home could reduce noise vibration and disputes between floors.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.181-191
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• 1991

The present study determined the overall noise level and the distribution of sound pressure level over audible frequency range of noise produced at various work sites. Work-related noise greater than 80dBA produced from 98 separate work sites at 37 manufacturing companies and machine shops were analysed for the overall sound level (dBA) and frequency distribution. In addition, to determine the possible hearing loss related to work site noise, a hearing test was also conducted on 1,374 workers in these work sites. The results of the study were as follows ; 1. Of the total 98 work sites, 57 work sites(58.2%) produced noise exceeding threshold limit value (${\geq}90dBA$) set by the Ministry 01 Labor. In terms of different manufacturing industries the proportion of work sites which exceeded 90dBA was the highest for the cut-stone products industry with 6/6 work sites and lowest for the commercial printing industry with 1/13 work sites. 2. The percentage of workers who were exposed to noise greater than 90dBA was 19.8% (1,040 workers) 01 the total 5,261 workers. In terms of different industries, cut-stone products industry had the most workers exposed to noise exceeding 90dBA with 82.8%, textile bleaching and dyeing industry was next at 30.6% followed by fabricated metal products industry with 27.9%, plastic products manufacturing industry had the lowest percentage of workers exposed to 90dBA exceeding noise with 4.5%. 3. There was a statistically significant correlation between the frequency of noise-induced hearing loss and the percentage of workers exposed to noise exceeding 90dBA (P<0.05). 4. The frequency analysis of noise produced at the 98 work sites revealed that 44 work sites (44.9%) had the maximum sound pressure level at high-frequencies greater than 2KHz. In addition, significantly higher sound pressure level was detected at the high-frequencies at 90dBA exceeding work sites as compared to below 90dBA work sites (P<0.01). 5. The differences in sound level meter's A-and C-weighted sound pressure levels were analysed by frequencies. Of the 28 work sites which showed 0-1 dB difference in the two weighted sound levels, 20 work sites (71.4%) had significantly higher sound pressure levels at high-frequencies greater than 2KHz (P<0.01). Furthermore, there was a tendency for higher sound pressure levels to occur in the high-frequency range as the differences in the two weighted sound levels decreased.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.197-205
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• 2017

We investigate the slat noise generation mechanism by using large-eddy simulation (LES) and simple source modeling based on linearized Euler equations. An incompressible LES of an MD 30P30N three-element airfoil in the high-lift configuration is conducted at $Re_c=1.7{\times}10^6$. Using the total derivative of the hydrodynamic pressure (DP/Dt) acquired from the incompressible LES, representative noise sources in the slat cove region are characterized in terms of simple sources such as frequency-specific monopoles and dipoles. Acoustic radiation around the 30P30N multi-element airfoil is effectively computed using the Brinkman penalization method incorporated with the linearized Euler equation. The directivity pattern of $p^{\prime}_{rms}$ at $r=20c_{slat}$ in the multiple sources is closely compared to that obtained by the application of the LES/Ffowcs-Williams and Hawking's methods to the entire flow field. The power spectrum of p' at ${\theta}=290^{\circ}$ is in good agreement with the data reported in BANC-III, especially the broadband part of the spectrum with a decaying slope ${\propto}f^{-3}$.

• Journal of Electrochemical Science and Technology
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• v.8 no.2
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• pp.115-123
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• 2017

Electrochemical noise signals in many cases exhibit a DC drift that should be removed prior to further data analysis. Polynomial fitting and moving average removal method have been used to remove trends of electrochemical noise (EN) in time domain. The corrosion inhibition of synthesized schiff base N,N'-bis(3,5-dihydroxyacetophenone)-2,2-dimethylpropandiimine on API-5L-X70 steel in hydrochloric acid solutions were used to study the effects of drifts removal methods on noise resistance calculation. Also, electrochemical impedance spectroscopy (EIS) was used to study the corrosion inhibition property of the inhibitor. The results showed that for the calculation of $R_n$, both methods were effective in trend removal and the polynomial with m=4 and MAR with p=40 were in agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.775-780
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• 2013

In recent years, a notebook like an ultrabook gets thinner. Its thickness causes problems in cooling fan performance, system installation condition, and so on. In this study, we installed a small turbofan in notebook system with very narrow gap in order to generate similar condition to a real product. Experiments were performed to measure the fan's performance and the flow and noise characteristics, its results were compared with computational ones. Prediction of P-Q curve using CFD showed under about 5% error in high flow rate and its trend was agreed with experimental one over the flow field. Experimental data to measure the noise at a distance of 100 mm from a rotation axis direction of an impeller corresponded well with computational ones of broadband and BPF noise. The noise experiments to measure at a distance of 100 mm from a rotation axis direction of an impeller corresponded well with computational ones of broadband and BPF noise. Especially, tip part of impeller blade and part of exit and bottom near in an analysis by a commercial program(FlowNoise).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.9-16
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• 2013

This paper experimentally deals with the excitation by functional electrical stimulus(FES) and the response of electromyo-potential at the muscles of antebrachial joint in a human body. The excitation of FES, which results in the contraction of the muscles and thus the flection of the joint, shows that the flection angle of the joint is proportional to the magnitude of the stimulus current. The response of electromyo-potential measured according to the FES shows the linearly-proportional relation between the joint torque and the electromyo-potential. The results can be used for active motion of joint rehabilitation.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.246-247
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• 2001

짧은 파장의 레이저 빔이 비선형 결정에 입사할 때 긴 파장의 두 광으로 자발적으로 변환하는 매개 하향변환(parametric down-convension; PDC)과정을 통해서 양자적 상관관계를 갖는 광원을 얻을 수 있다. PDC 과정은 에너지 보존 (w$_{p}$ = w$_{s}$ ＋ w$_{i}$)과 운동량 보존 (k$_{p}$ = k$_{s}$ ＋ k$_{i}$)에 해당하는, 위상조화 (phase matching) 조건이 잘 만족할 때 효과적으로 일어난다. PDC에서 광자들이 아주 짧은 시간에 쌍으로 발생한다는 것과 이러한 광자쌍을 동시에 측정하는(coincidence count; 동시계수) 방법을 이용하면 효과적으로 신호와 잡음을 분리해 낼수 있고, 배경(background)이나 잡음(noise)보다 미약한 신호를 통해서도 정보를 전달할 수 있는 가능성을 제공해준다. (중략)