• The Journal of the Acoustical Society of Korea
• /
• v.33 no.6
• /
• pp.375-382
• /
• 2014

In many practical active noise control applications, the primary noise contains multiple closely-spaced harmonics. A narrowband ANC system consists of adaptive filters excited by a composite reference signal, which is the set or sum of sinusoids. This paper analyzes and shows that the convergence speeds of the direct form, parallel form, and simplified parallel form narrowband ANC systems are affected by the fundamental frequency and frequency separation between two adjacent sinusoids in the reference signal. This paper also proposes the new simplified parallel form narrowband ANC system whose convergence speed is independent on the frequency of the reference signal. Computer simulations are conducted to verify the analysis presented in the paper and to compare the proposed narrowband ANC system with the conventional narrowband ANC system.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.7
• /
• pp.1069-1076
• /
• 2012

We use largely two methods, how to control the noise of the KTX, they are the passive noise control method and the active noise control method. The passive noise control has been used in a variety of ways since the KTX opening day, but lately it has shown the technical limitations by being dropped sharply. So, it is getting important to conduct the research about ANC that is able to reduce the ambient noise when the environmental-factor changes and be installed easily. To reduce a three-dimensional closed-space sound field like a car of a high-speed rail is hard to do using single channel ANC control system. Therefore we have to model the paths of the noise exactly for reducing the noise. And the control speakers and the error mics should be designed for optimal position. In this paper, we designed the transfer functions for modeling the noise paths under the influence of the distance between control speakers & error mics and primary noise speaker in TEST-BED where there is modeled as actual interior of KTX. We have made the modeling and the simulations of interior environment of KTX car by using three frequency bands of 120Hz, 280Hz, 360Hz. After the modeling, we compared the performance of active noise control and also we analyzed what to affect with difference in distance. After comparing of the performance using Pure Tone 120Hz, 280Hz, 360Hz at each modeling and then we simulated ANC for KTX's interior noise which we measured really and analyzed.

• Clinical and Experimental Pediatrics
• /
• v.50 no.10
• /
• pp.982-986
• /
• 2007

Purpose : Intravenous immunoglobulin (IVIG) is effective for the treatment of idiopathic thrombocytopenic purpura (ITP) in children. Recently, several reports have been published that show its impact on the absolute neutrophil count. The present study was performed to confirm these findings. Methods : Data on 26 ITP patients were analyzed. Patients with febrile illness or increased C-reactive protein levels at presentation, which would influence the neutrophil counts, were excluded to determine the sole impact of IVIG. In addition, patients who received steroid treatment were also excluded. Results : Sixteen boys and ten girls were analyzed. For patients who received an IVIG dose of 0.4 g/kg/day (n=17), the absolute neutrophil count (ANC) measured next day was significantly decreased. For patients who received an IVIG dose of 1 g/kg/day (n=9), the ANC measured the next day was also significantly decreased. However, the decrease was more profound in the high-dose group compared to the low-dose group. Among six cases with profoundly decreased ANC greater than $1,000/mm^3$, four patients (67%) received IVIG at a dose of 1 g/kg/day. All four cases with increased ANC were treated with IVIG dose of 0.4 g/kg/day, and three cases (75%) among them had a febrile reaction during IVIG administration. None of the cases with decreased ANC had a febrile reaction. No cases had infectious complications reported. Conclusion : IVIG treatment for ITP patients appears to suppress the ANC. This decrease of ANC was more pronounced when a higher dose of IVIG was used. Some cases with increased ANC counts after IVIG use were found only in low-dose IVIG group, and was associated with febrile reactions during IVIG use.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.97-98
• /
• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.111-112
• /
• 2011

• Clinical and Experimental Pediatrics
• /
• v.51 no.2
• /
• pp.204-208
• /
• 2008

Purpose : The aim of this study was to investigate the incidence and course of neutropenia following intravenous immunoglobulin (IVIG) therapy in children with idiopathic thrombocytopenic purpura (ITP). Methods : From January 2001 to June 2006, fifty-four patients with ITP were enrolled in this study. Forty-two of 54 patients were treated with IVIG, while the other 12 were treated with anti-D immunoglobulin (Anti-D Ig). Post-treatment absolute neutrophil counts (ANC) were compared between patients who received IVIG and those who received Anti-D Ig. Comparison of post-treatment ANC between patients who treated with two different IVIG regimens (400 mg/kg/day for 5 days and 1 g/kg/day for 2 days) was also performed. Results : Pretreatment ANC were not significantly different between the two treatment groups. After treatment with IVIG, 32 out of 42 patients (76.2%) showed more than 50% decrease of ANC from the baseline. On the other hand, only 2 out of 12 patients (16.7%) showed more than 50% decrease of ANC from the baseline after treatment Anti-D Ig. No significant difference was observed in the decline of ANC between the first IVIG treatment (42 patients) and repeated IVIG treatment groups (7 patients). There was no statistical difference in post-treatment ANC between patients who treated with two different IVIG regimens. The neutropenia induced by IVIG had resolved spontaneously in 38 out of 39 patients (97%) after several days. Conclusion : Neutropenia following IVIG administration may not be an uncommon finding in children with ITP. It seems to be transient and self limited.

• International Journal of Highway Engineering
• /
• v.17 no.6
• /
• pp.11-18
• /
• 2015

PURPOSES : The purpose of this thesis is to evaluate the effectiveness of an active noise cancellation (ANC) system in reducing the traffic noise level against frequencies from the predictive model developed by previous research. The predictive model is based on ISO 9613-2 standards using the Noble close proximity (NCPX) method and the pass-by method. This means that the use of these standards is a powerful tool for analyzing the traffic noise level because of the strengths of these methods. Traffic noise analysis was performed based on digital signal processing (DSP) for detecting traffic noise with the pass-by method at the test site. METHODS : There are several analysis methods, which are generally divided into three different types, available to evaluate traffic noise predictive models. The first method uses the classification standard of 12 vehicle types. The second method is based on a standard of four vehicle types. The third method is founded on 5 types of vehicles, which are different from the types used by the second method. This means that the second method not only consolidates 12 vehicle types into only four types, but also that the results of the noise analysis of the total traffic volume are reflected in a comparison analysis of the three types of methods. The constant percent bandwidth (CPB) analysis was used to identify the properties of different frequencies in the frequency analysis. A-weighting was applied to the DSP and to the transformation process from analog to digital signal. The root mean squared error (RMSE) was applied to compare and evaluate the predictive model results of the three analysis methods. RESULTS : The result derived from the third method, based on the classification standard of 5 vehicle types, shows the smallest values of RMSE and max and min error. However, it does not have the reduction properties of a predictive model. To evaluate the predictive model of an ANC system, a reduction analysis of the total sound pressure level (TSPL), dB(A), was conducted. As a result, the analysis based on the third method has the smallest value of RMSE and max error. The effect of traffic noise reduction was the greatest value of the types of analysis in this research. CONCLUSIONS : From the results of the error analysis, the application method for categorizing vehicle types related to the 12-vehicle classification based on previous research is appropriate to the ANC system. However, the performance of a predictive model on an ANC system is up to a value of traffic noise reduction. By the same token, the most appropriate method that influences the maximum reduction effect is found in the third method of traffic analysis. This method has a value of traffic noise reduction of 31.28 dB(A). In conclusion, research for detecting the friction noise between a tire and the road surface for the 12 vehicle types needs to be conducted to authentically demonstrate an ANC system in the Republic of Korea.

• The Journal of the Acoustical Society of Korea
• /
• v.34 no.5
• /
• pp.377-384
• /
• 2015

An active noise control (ANC) algorithm for noise canceling headphone is proposed. In this study, the feedback ANC operated with the filtered-x least mean square algorithm (FxLMS) algorithm is used to attenuate the undesired noise. Also an adaptive residual music canceller (RMC) is proposed for enhancing the accuracy of the reference signal of the feedback ANC. Simulation results show that a high quality of music sound can be consistently achieved in a time-varying secondary path situation.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.7
• /
• pp.51-57
• /
• 2009

In this paper, we studied on an attenuation effect of automobile exhaust noise according to the direction of canceling speaker in duct-acoustic ANC system. Automobile exhaust noise was recorded at 800rpm, 3500rpm and 5000rpm of a diesel engine. Directions of canceling speaker can be set to $30^{\circ}$, $90^{\circ}$ and $150^{\circ}$ against the primary noise flow by acrylic ducts to be made for the experimentation. DSP board used to control the ANC system. The algorithm of this ANC system applied the Filtered-x-LMS algorithm that is modified to compensate for a property of DSP input signal and the secondary-path effect. As an experiment result, the direction of canceling speaker was proved to influence the reduction effect of noise. The $150^{\circ}$ duct in the attenuation effect of noise showed a better result than the $90^{\circ}$ or $30^{\circ}$ duct.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.325-326
• /
• 2009

The present study concerns the acid neutralization capacity (ANC) of cement paste, mortar and concrete depending on a free water-cement ratio. The ANC of paste at 30%, 40% and 50% of water-cement ratio was measured and simultaneously the effect of aggregate on the ANC was evaluated. It was found that an increase in the acid concentration resulted in a decrease in the pH of the suspension, in particular, at 10 in the pH, a sharp decrease was observed. The ANC showed some peak resistances to acid at particular pH values.