The performance of sound barriers was evaluated to determine their technical effectiveness and practicality in reducing noise exposures to operating engineers in construction. Commercially purchased sound dampening mats (SDMats) were installed inside three heavy-equipment engine compartments. Sound pressure levels (SPLs) were measured before and after installing the SDMats while the equipment was on idle and full-throttle settings where it normally operates. SPLs inside the heavy-equipment operator cabs were significantly reduced by 5.6–7.6 dBA on the full-throttle setting following installation of the SDMats (p < 0.01). The evaluated engineering control intervention was simple to install, affordable, and substantially reduced the engine noise reaching the heavy-equipment operator, potentially reducing reliance on hearing-protection devices to protect construction workers from noise exposures.
Noise*

Three-dimensional (3-D) ultrasonographic imaging techniques have recently shown rapid development and theirclinical application has begun to attract considerable at-tention. Power Doppler sonography is known to be moresensitive than color Doppler for detecting blood flow, and there is also less noise and clutter. This paperdescribes the basic principles and initial clinical experience of 3-D power Doppler sonography.
Noise

No abstract available.
Noise* ; Tinnitus*

In this paper, we propose 2D segmentation algorithm for 3D visualization using CT bone images. Kmeans algorithm and thresholding method are traditional methods that can detect human bone. But the noise appeared on segmented images generated by both Kmeans algorithm and thresholding method. To detect bone cluster, the two assumptions are considered, they are as follows; first, pixels that have high intensity can be merged into bone cluster. Secondly, because a bone cluster consists of large or small group, the ambiguous pixels can be merged into bone cluster by estimating segmentation function. With the proposed FSTB(Flexible Segmentation To Boundary) algorithm the noise didn't appeared on segmented CT bone images and the algorithm carried out effective segmentation to the ambiguous pixels.
Humans ; Noise

BACKGROUND: Evaluation of the quality of tinnitus is very useful for understanding of the nature of tinnitus by non-sufferers including physicians. But tinntus matching with pure tone is a limited access to qualify tinnitus and frequently it is difficult for sufferer to match and this may be an important cause of low test-retest reliability. OBJECTIVES: The aim of this study are to identify sounds mimicking tinnitus using generated and environmental sounds and its reliability on repeated tests. MATERIALS AND METHODS: 34 patients(M: 22, F: 12) who have suffered from continuous tinnitus were selected. Electronically generated sounds were pure tone, narrow band(1/3 octave band width) noise filtered from gaussian noise, random frequency band sine waves with center frequency. Twenty artificial and fourteen natural environmental sounds were recorded and calibrated. The most similar sound were selected by sufferer three times at the minimum time interval 2 weeks. The frequency spectrums of environmental sounds were analyzed. RESULTS: The most similar sounds mimicking tinnitus were pure tone(29.2%), frequency modulated sine wave(27.1%), natural environmental sounds(20.8%), narrow bane noise(14.6%), artificial environmental sounds(12.5%) in order. The reliability of the selection of the most similar sounds on repeated tests were very high(94.1%). The spectrum of the environmental sounds selected were broad. CONCLUSIONS: The quality of tinitus can be evaluated more objectively by electronically generated sounds which are highly reproducible. The quality of tinnitus is quite consistent. Also in the majority, the quality of tinnitus is different from the quality of pure tone.
Noise ; Tinnitus*

In this study, we have conducted characterization of imaging performance for a flat panel digital X-ray detector using amorphous Selenium and a-Si TFT which was developed by the authors. The procedures for characterization were in concordance with internationally recommended standards such as IEC (international electrotechnical commission). The measures used for imaging performance characterization include response characteristic, modulation transfer function (MTF), detective quantum efficiency (DQE), noise power spectrum (NPS), and quantum limited performance. The measured DQEs at lowest and highest spatial frequencies were 40% and 25% respectively, which was superior to that of commercial products by overseas vendor. The MTF values were significantly superior to that of CR and indirect type DRs. The quantum limited performance showed the detector was limited by quantum noise at the entrance exposure level below 0.023 mR, which is sufficiently low for general X-ray examination.
Commerce ; Noise ; Selenium ; Silicon

Air pollution in the traffic areas in Seoul during the winter season was studied. The average level of sulfur dioxide concentration was 0.24 ppm through the day. Lowest was 0.14 ppm at 2~4 P.M. when the highest vertical temperature gradient was indicated, and 0.33~0.29 ppm during 10 P.M. to 8 A.M. at night. Average level of dust was 4.65 mppcf (2.1~12.8 mppcf) and higher levels were shown at 10 A.M., 6 P.M. and 10 P.M. as 5.44, 4.73 and 5.01 mppcf respectively. The noise level in the main traffic areas was 73.5 db in the average during this survey, 75.1 db in the daytime and 65.6 db in the night (11 P.M. ~7 A.M.) in the average. Various air pollutants in auto-exhaust gases and noise of automobiles were studied, since those are main sources of nuisance in the traffic areas. Carbon monoxide in the "Corona" taxi, formaldehyde in the jeep, and carbon monoxide, formaldehyde and sulfur dioxide in the "Senara" taxi were measured respectively in high concentration and there was no significant difference in other gases among the various type of vehides. As regards average Overall noise level at ordinary driving speeds, heavy vehicles emitted much more noise (30 KPH) (82.2~83.5 db) than light vehicles such as taxi (40~5O KPH) (71.5-80.2 db). The noise level when starting heavy vehicles was higher 88.5 db(94.2 phon) on the average and that of light vehicles was lower 69.4 db (76.2 phon). There were two types of automobile horn noise in the octave band; one was in 1,000 cps and the other 2,000~4,000cps. The average horn noise level of automobiles was 98 db (107.8 phon), with 106 db (11.05 phon) maximum and 88.8db (99.5 phon) minimum. In the epidemiological study of CO poisoning in urban areas, there were 260 deaths out of 532 patients in 201 incidents of poisoning occurring on a total of 128 days during January 1964 to Dec. 1966. The concentration of co in the main living rooms and kitchens was detected as 58 and 112 ppm respectively, and the level of carboxyl-hemoglobin in the blood of housewives was relatively high, 11.2% on the average. In outside air maximal concentration of CO was 80 ppm in Shinchon-Dong an urban area.
*Air Pollution ; Korea ; *Noise

PURPOSE: Dedicated animal PET is useful equipment for the study of new PET tracer. Recently, microPET R4 was installed in the Korea institute of radiology and medical science. In this study, we measured the characteristics of scanner. MATERIALS AND METHODS: Resolution was measured using a line source (F-18: 65 micro Ci, inner diameter: 0.5 mm). The line source was put in the axial direction and was moved from the center of field of view to outside with 1 mm interval. PET images were reconstructed using a filtered back-projection and ordered subset expectation maximization. Line source (16.5 micro Ci, 78 mm) was put on the center of axial direction to measure the sensitivity when the deadtime was under 1%. Images were acquired during 4 minutes respectively from center to 39 mm outward. Delayed count was subtracted from total count and then decay was corrected for the calculation of sensitivity. Noise equivalent count ratio and scatter fraction were calculated using cylindrical phantom. RESULTS: Spatial resolution of reconstructed image using filtered back-projection was 1.86 mm (radial), 1.95 mm (tangential), 1.95 mm (axial) in the center of field of view, and 2.54 mm, 2.8 mm, 1.61 mm in 2 cm away from the center respectively. Sensitivity was 2.36% at the center of transaxial field of view. Scatter fraction was 20%. Maximal noise equivalent count ratio was 66.4 kcps at 242 kBq/mL. Small animal images were acquired for confirmation of performance. CONCLUSION: Performance characteristics of microPET R4 were similar with reported value. So this will be a useful tool for small animal imaging.
Animals* ; Korea ; Noise

PURPOSE: We wanted to evaluate an acceptable compression rate of JPEG2000 for long term archiving of CT and MR images in PACS. MATERIALS AND METHODS: Nine CT images and 9 MR images that had small or minimal lesions were randomly selected from the PACS at our institute. All the images are compressed with rates of 5:1, 10:1, 20:1, 40:1 and 80:1 by the JPEG2000 compression protocol. Pairs of original and compressed images were compared by 9 radiologists who were working independently. We designed a JPEG2000 viewing program for comparing two images on one monitor system for performing easy and quick evaluation. All the observers performed the comparison study twice on 5 mega pixel grey scale LCD monitors and 2 mega pixel color LCD monitors, rspectively. The PSNR (Peak Signal to Noise Ratio) values were calculated for making quantitative comparisons. RESULTS: On MR and CT, all the images with 5:1 compression images showed no difference from the original images by all 9 observers and only one observer could detect a image difference on one CT image for 10:1 compression on only the 5 mega pixel monitor. For the 20:1 compression rate, clinically significant image deterioration was found in 50% of the images on the 5M pixel monitor study, and in 30% of the images on the 2M pixel monitor. PSNR values larger than 44 dB were calculated for all the compressed images. CONCLUSION: The clinically acceptable image compression rate for long term archiving by the JPEG2000 compression protocol is 10:1 for MR and CT, and if this is applied to PACS, it would reduce the cost and responsibility of the system.
Data Compression ; Noise

PURPOSE: NEMA NU2-2001 was proposed as a new standard for performance evaluation of whole body PET scanners. In this study, system performance of Siemens CTI ECAT EXACT 47 PET scanner including spatial resolution, sensitivity, scatter fraction, and count rate performance in 2D and 3D mode was evaluated using this new standard method. METHODS: ECAT EXACT 47 is a BGO crystal based PET scanner and covers an axial field of view (FOV) of 16.2 cm. Retractable septa allow 2D and 3D data acquisition. All the PET data were acquired according to the NEMA NU2-2001 protocols (coincidence window: 12 ns, energy window: 250 ~ 650 keV). For the spatial resolution measurement, F-18 point source was placed at the center of the axial FOV ( (a) x=0, and y=1, (b) x=0, and y=10, (c) x=10, and y=0cm) and a position one fourth of the axial FOV from the center ( (a) x=0, and y=1, (b) x=0, and y=10, (c) x=10, and y=0cm). In this case, x and y are transaxial horizontal and vertical, and z is the scanner's axial direction. Images were reconstructed using FBP with ramp filter without any post-processing. To measure the system sensitivity, NEMA sensitivity phantom filled with F-18 solution and surrounded by 1~5 aluminum sleeves were scanned at the center of transaxial FOV and 10 cm offset from the center. Attenuation free values of sensitivity were estimated by extrapolating data to the zero wall thickness. NEMA scatter phantom with length of 70 cm was filled with F-18 or C-11solution (2D: 2, 900 MBq, 3D: 407 MBq), and coincidence count rates were measured for 7 half-lives to obtain noise equivalent count rate (NECR) and scatter fraction. We confirmed that dead time loss of the last frame were below 1%. Scatter fraction was estimated by averaging the true to background (scatter + random) ratios of last 3 frames in which the fractions of random rate are negligibly small. RESULTS: Axial and transverse resolutions at 1cm offset from the center were 0.62 and 0.66 cm (FBP in 2D and 3D), and 0.67 and 0.69 cm (FBP in 2D and 3D). Axial, transverse radial, and transverse tangential resolutions at 10cm offset from the center were 0.72 and 0.68 cm (FBP in 2D and 3D), 0.63 and 0.66 cm (FBP in 2D and 3D), and 0.72 and 0.66 cm (FBP in 2D and 3D). Sensitivity values were 708.6 (2D), 2931.3 (3D) counts/sec/MBq at the center and 728.7 (2D), 3398.2 (3D) counts/sec/MBq at 10 cm offset from the center. Scatter fractions were 0.19 (2D) and 0.49 (3D). Peak true count rate and NECR were 64.0 kcps at 40.1 kBq/mL and 49.6 kcps at 40.1 kBq/mL in 2D and 53.7 kcps at 4.76 kBq/mL and 26.4 kcps at 4.47 kBq/mL in 3D. CONCLUSION: Information about the performance of CTI ECAT EXACT 47 PET scanner reported in this study will be useful for the quantitative analysis of data and determination of optimal image acquisition protocols using this widely used scanner for clinical and research purposes.
Aluminum ; Architectural Accessibility ; Noise