• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.193-199
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• 1995

This study was designed to investigate the difference of time weighted average(TWA) of noise levels and noise doses by the different operating parameter settings such as exchange rate, threshold level and criterion level for noise dosimeter in the field measurements of noise at industrial working environments. The time weighted averages of noise level and noise doses for noise working environments were determined by noise dosimeter on 80 workers employed at 20 industrial establishments of 8 industries. The results obtained were as follows: 1. The mean time weighted average(TWA) of the noise working environments by the operating parameter settings showed 93.4 dB(A) in 3 dB of exchange rate, 80 dB of threshold level and 90dB of criterion level 92.0 dB(A) in 3 dB-exchange rate, 90 dB-threshold level and 90 dB-criterion level, in 90.8 dB(A) in 5 dB of exchange rate, 80 dB of threshold level and 90 dB of criterion level, and 86.7 dB(A) in 5 dB of exchange rate, 90 dB of threshold level and 90dB of criterion level. 2. ln group of noise level less than 90 dB(A), mean TWAs of 80 dB of threshold level were significantly higher than that of 90 dB of threshold level in 3 dB and 5 dB of exchange rate. 3. The case exceeded threshold limit value of noise was 49(61.3 %) in 3dB, 80dB and 90 dB setting, 44(55.0 %) in 3 dB, 90 dB, 90 dB setting, 33(41.3 %) in 5 dB, 80dB, 90 dB setting and 26(32.5%) in 5 dB, 90 dB, 90 dB setting. Above considerations in mind, it is suggested that exchange rate and threshold level be specified in related laws and regulations in the evaluation of working environments noise.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.3
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• pp.308-316
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• 2023

Objectives: The aim of this study is to measure and assess the occupational noise exposure levels among construction workers at apartment building construction sites in South Korea. Methods: Noise exposure assessments were conducted for 139 construction workers across 10 different trades at 53 apartment building construction sites in the northern part of Gyeonggi-do. Assessments were carried out using a noise dosimeter set with a 90 dB criterion, an 80 dB threshold, and a 5 dB exchange rate over a period of more than 6 hours(L_MOEL) Results: The mean L_MOEL (equivalent continuous noise level over 8 hours) for the 139 dosimeter samples was 87.8 ± 4.3 dBA. The mean noise exposure level for each construction trade, referred to as the trade mean, was also calculated. Significant differences in noise exposure levels were observed between construction trades (ANOVA, p < 0.001). The highest L_MOEL values were recorded for concrete chippers (93.2 ± 2.6 dBA), followed by ironworkers (88.4 ± 0.7 dBA), concrete finishers (88.3 ± 2.7 dBA), masonry workers (87.7 ± 1.9 dBA), pile driver operators (85.6 ± 1.7 dBA), concrete carpenters (84.9 ± 2.4 dBA), interior carpenters (83.5 ± 2.1 dBA), and other groups (81.4 ± 2.2 dBA). Conclusions: The findings suggest that nearly all construction workers in this study are at risk of Noise-Induced Hearing Loss (NIHL). Moreover, the study establishes that construction trades can serve as a useful metric for assessing noise exposure levels at apartment construction sites.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.739-744
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• 2013

The aim of this study is to evaluate the noise level from the machines used for tunnel construction and to analyze the noise exposure level of workers engaged in tunneling works. The sound level meter and noise dosimeters was used for the monitoring of noise in the tunneling work sites. The average noise from jumbo drill was 113.0 dE(A), the noise from pay loader was 92.4 dB(A), the noise from backhoe was 99.9 dB(A) and the noise from shotcrete machine was 94.3 dE(A). The tunneling workers were exposed to 66.9~94.9 dB(A) of noise and other workers exposed to less than 90 dB(A) of noise. Jumbo drill operators were exposed to to 82.5~84.2 dB(A) of noise, backhoe operators were exposed to 70.2~94.9 dB(A) of noise, shotcrete machine operators were exposed to 68.2~74.7 dB(A) of noise and pay loader operators were exposed to 59.2~81.3 dE(A) of noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.9
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• pp.831-840
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• 2013

The noise levels of workers in tunnel sites are likely to be high because tunneling work places are confined space. However, research on the noise exposure levels of tunneling workers have not been performed intensively due to restricted accessibility to tunnel construction sites. The aim of this study is to evaluate the noise exposure levels for workers engaged in tunneling work sites. Noise dosimeters were used for monitoring workers' noise exposure level in 5 tunneling work sites in accordance with the Notification of the Ministry of Labor. Among 5 tunneling work sites, 4 of them used NATM tunneling method and 1 work site used shield TBM tunneling method. The average noise exposure levels of NATM tunneling workers was 81.1 dB(A) and 15.4 % of the workers' noise level were exposed more than 90 dB(A) which is the exposure limit value. In Shield TBM tunneling method, 4.3 % of the workers were exposed more than 90 dB(A) of noise level, the average noise exposure levels of TBM tunneling workers was 84.1 dB(A).

• Safety and Health at Work
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• v.2 no.4
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• pp.348-354
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• 2011

Objectives: This cross-sectional study was performed in the Dental School of Prince of Songkla University to ascertain noise exposure of dentists, dental assistants, and laboratory technicians. A noise spectral analysis was taken to illustrate the spectra of dental devices. Methods: A noise evaluation was performed to measure the noise level at dental clinics and one dental laboratory from May to December 2010. Noise spectral data of dental devices were taken during dental practices at the dental services clinic and at the dental laboratory. A noise dosimeter was set following the Occupational Safety and Health Administration criteria and then attached to the subjects' collar to record personal noise dose exposure during working periods. Results: The peaks of the noise spectrum of dental instruments were at 1,000, 4,000, and 8,000 Hz which depended on the type of instrument. The differences in working areas and job positions had an influence on the level of noise exposure (p < 0.01). Noise measurement in the personal hearing zone found that the laboratory technicians were exposed to the highest impulsive noise levels (137.1 dBC). The dentists and dental assistants who worked at a pedodontic clinic had the highest percent noise dose (4.60 ${\pm}$ 3.59%). In the working areas, the 8-hour time-weighted average of noise levels ranged between 49.7-58.1 dBA while the noisiest working area was the dental laboratory. Conclusion: Dental personnel are exposed to noise intensities lower than occupational exposure limits. Therefore, these dental personnel may not experience a noise-induced hearing loss.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.11
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• pp.854-860
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• 2014

Workers engaged in car inspection works have been exposed to many occupational hazards including noise, particulate matter, and volatile organic substances. Noise-induced hearing loss(NIHL) is one of the leading health hazards among Korean workers. The aim of this study is to evaluate the noise levels in several car inspection shops by introducing the evaluation methods of KMOEL/OSHA and ACGIH. Six sites in central area of Korea were selected to monitor the noise levels of workers by personal and area sampling methods for two consecutive days in spring, summer, fall and winter seasons. Dosimeters have been used for this noise monitoring program. Obtained noise levels by the evaluation method according to KMOEL/OSHA are the range of 50.2~88.2 dB(A), these are lower than KOEL/OSHA standards level of 90 dB(A). But highest noise by ACGIH's evaluation methodology is recorded 92.3 dB(A) and is greater than NIHL standard level of 85 dB(A). So that many workers may be exposed to the dangerous noise environment. The higher the car inspection loads daily, the higher the noise levels in the sites. Seasonal fluctuation of noise levels at the process might give monitoring results with high variations. Area noise levels showed higher than those of personal sampling, which illustrate some high noise spots in the car inspection areas.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.190-197
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• 2001

Noise-induced hearing loss(NIHL) was the highest rate (43.5%~58.5% from 1996 to 1998) of positive findings through specific medical program in Korea. There were much more NIHL at workers of automobile manufacturing factories than other manufacturing factories. The specific aim of the present study was to determine the noise exposure of automobile press lines, according to their job titles, press line types(auto, semiauto), dosimeter parameters setting. There were a total 11 press lines sampled at a automobile manufacturing company. Among those press lines, 10 press lines were autolines with acoustic enclosure, one semiauto press line was no aucostic enclosure Noise exposure data were sampled for an work shift using noise dosimeter, which recorded both time-weighted average(TWA) and 1-min average. The mean OSHA TWA(Korea TWA with threshold 90) was $80.7dB(A){\pm}4.7dB(A)$ for leader, $82.8dB(A{\pm}4.5dB(A)$ for pallette man, $76.7dB(A){\pm}4.3dB(A)$ for press operators, $76.6dB(A){\pm}5.6dB(A)$ for crane operators, $77.1dB(A){\pm}2.8dB(A)$ for forklift drivers, whereas the mean NIOSH TWA was $88.9dB(A){\pm}1.7dB(A)$ for leader, $89.6dB(A){\pm}2.1dB(A)$ for pallette man, $86.7dB(A){\pm}1.8dB(A)$ for press operators, $88.5dB(A){\pm}2.0dB(A)$ for crane operators, $87.7dB(A){\pm}1.0dB(A)$ for forklift drivers. While L10 for NIOSH TWA samples was 84.8 dB(A) ~ 87.3 dB(A), L10 for OSHA TWA samples was 69.5 dB(A) ~ 77.4 dB(A). L10 means that the TWA for 90% of the samples exceeded L10. Among OSHA TWA(Korea TWA with threshold 90) samples for pallette man, 7.7 % exceeded 90 dB(A), the OSHA permissible exposure level, but OSHA TWA samples for the other job titles didn't. Among NIOSH TWA samples, the samples over 85 dB(A), the NIOSH recommended exposure limit, was 100% (leaders), 83.3 %(operators), 97.4%(palletteman), 100%(forklift drivers), 91.7 %(crane operator). The results of One-way random effects analysis of variance models shows that the difference between job titles was significant by OSHA TWA(p<0.05), but not significant by NIOSH TWA(p>0.05). NIOSH TWA samples were significantly higher than OSHA TWA samples(P<0.05). Regression analysis was used to obtain relationships between OSHA TWA samples and NIOSH TWA samples. In this case the coefficient of determination = 0.90, which shows the high degree association between two methods. Regression equation, NIOSH TWA = 0.552 * OSHA TWA + 42.13 dB(A), shows that if OSHA TWA is known, NIOSH TWA can be predicted by the equation. The mean TWA difference between threshold 80 dBA and 90 dBA was significant(p<0.01). While the TWA noise exposures were 7.7% above the Korea(OSHA) PEL, they were more than 83.3% over NIOSH REL. Automobile workers were exposed to noise level that could be potentially damaging to their hearing. It found that there is approximately 25% excess risk of hearing loss even if a worker is protected to the PEL in according to NIOSH study.

• Progress in Medical Physics
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• v.21 no.1
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• pp.1-8
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• 2010

In this study, we evaluated the dose response of MAGAT (Methacrylic Acid Gelatin gel and THPC) normoxic polymer gel dosimeters based on the X-ray CT scanner. To perform this study, we determined the proper ratio of the gel composition and acquired X-ray scan parameters. MAGAT gel dosimeters were manufactured using MAA (MethacrylicAcid) and gelatin of various concentration, irradiated up to 20 Gy. We obtained the 20 CT images from the irradiated gel dosimeters by using on a Phillips Brilliance Big Bore CT scanner with the various scan parameters. This CT images were used to determine the $N_{CT}$-dose response, dose sensitivity and dose resolution As an amount of MAA and gelatin were increase, the slope and intercept were increase in each MAGAT gel dosimeter with various concentration of the $N_{CT}$-dose response curve. The dose sensitivity was $0.38{\pm}0.08$ to $0.859{\pm}0.1$ and increased were amount of the MAA was increased or the gelatin was decreased. However, the change of gelatin concentration was very small compare to MAA. The Dose resolution ($D_{\Delta}^{95%}$) varies considerably from 2.6 to 6 Gy, dependent on dose resolution and CT image noise. The slope and dose sensitivity was almost ident verywith the variation of the tube voltage, tube current and slice thickness in the dose response curve, but the noise (standard deviation of averamalg CT number) was decreased when the tube voltage, tube current and slice thickness are increase. The optimal MAGAT polymer gel dosimeter based on the CT were evaluated to determine the CT imaging scan parameters of the maximum tube voltage, tube current and slice thickness (commonly used in clinical) using the composition ratio of a 9% MAA, 8% gelatin and 83% water. This study could get proper composition ratio and scan parameter evaluating dose response of MAGAT normoxic polymer gel dosimeter using CT scanner.

• Journal of radiological science and technology
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• v.47 no.3
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• pp.167-173
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• 2024

This study purpose to establish an appropriate target exposure index(EIT) using dose area product(DAP) and exposure index(EI) based on chest radiography. First, the system response experiment was conducted with radiation quality of RQA5 to compare the dosimetry and dose area product of equipment. Next, EI and DAP were acquired and analyzed while varying the dose in the diagnostic at 70kVp using a human body model phantom. The signal to noise ratio(SNR) of the obtained results was analyzed in the diagnostic with in the diagnostic reference level(DRL) application range. The DRL at percentage 25% had a dose of 0.17 mGy and EI was 83, and at percentage 75% the dose was 0.68 mGy and EI was 344. As the dose increased, the SNR in the subdiaphragm increased. To set the EIT, calibration must first be performed using a dosimeter and set within the DRL range to reflect the needs of the medical institution.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.99-106
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• 2023

The height of the table should be considered important during computed tomography (CT) examination, but according to previous studies, not all radiology technologists set the table at the patient's center at the examination, which affects the exposure dose and image quality received by the patient. Therefore, this study intends to study the image quality exposure dose according to the height of the table to realize the optimal image quality and dose during the brain CT scan. The head phantom images were acquired using Philips Brilliance iCT 256. When the image was acquired, the table height was adjusted to 815, 865, 915, 965, 1015, and 1030 mm, respectively, and each scan was performed 3 times for each height. For the exposure dose measurement, optically stimulated luminescence dosimeter (OSLD) was attached to the front, side, eye, and thyroid gland of the head phantom. In the signal to noise ratio (SNR) measurement result, The SNR values for each table height were all lower than 915 mm. As a result of exposure dose, the exposure dose on each area increased as the table height decreased. The height of the table has a close relationship with the patient's radiation exposure dose in the CT scan.