• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.12
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• pp.1237-1242
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• 2008

A muffler design in the exhaust system is critical to provide fur low noise in shipboard spaces. In an attempt to effectively design the low noise muffler, it Is important to evaluate the performance of the muffler considering not only the noise, but also pressure drop as well. For this purpose, a test system of large exhaust mufflers fur ship propulsion systems was designed based on ISO 7235. The substitution test fur determining both the insertion loss and pressure drop of mufflers was carried out. A ship exhaust muffler is considered as a test example and the insertion loss and pressure drop were obtained.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.423-426
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• 2003

Adaptive algorithm used in Acoustic Echo Canceller (AEC) needs fast convergence algorithm when reference signal is colored speech signal. Set-Membership Affine Projection (SMAP) algorithm is derived from the constraint, which is the minimum value adaptive filter coefficient error. In this paper, we test the characteristic about noise of the SMAP algorithm and proposed modified version of SMAP algorithm fur using at AEC. As the projection order increase, the convergence characteristic of the SMAP algorithm is improved where no noise space. But if the noise uncorrelated with input signal exists, the AEC shows bad performance. In this paper, we propose normalized version of adaptive constants using estimated error signal for robust to noise and show the good performance through AEC simulation.

• Current Optics and Photonics
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• v.5 no.5
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• pp.562-575
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• 2021

As a new type of spectrometer, that based on filters with different transmittance features attracts a lot of attention for its advantages such as small-size, low cost, and simple optical structure. It uses post-processing algorithms to achieve target spectrum reconstruction; therefore, the performance of the spectrometer is severely affected by noise. The influence of noise on the spectral reconstruction results is studied in this paper, and suggestions for solving the spectral reconstruction problem under noisy conditions are given. We first list different spectral reconstruction methods, and through simulations demonstrate that these methods show unsatisfactory performance under noisy conditions. Then we propose to apply the gradient projection for sparse reconstruction (GRSR) algorithm to the spectral reconstruction method. Simulation results show that the proposed method can significantly reduce the influence of noise on the spectral reconstruction process. Meanwhile, the accuracy of the spectral reconstruction results is dramatically improved. Therefore, the practicality of the filter-based spectrometer will be enhanced.

• Journal of Broadcast Engineering
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• v.26 no.3
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• pp.327-330
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• 2021

In this paper, a new noise filling method is proposed for improving the performance of the 3D audio codec. In the new method, the core band is limited up to MAX_SFB, not up to the IGF start frequency. And the noise filling is applied to all frequency range of the IGF source patches. We conduct the MUSHRA test and find that the proposed noise filling method demonstrates better performance than the conventional method.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.5
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• pp.38-43
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• 1996

Windowing routines have as their purpose the reduction of the sidelobes of a spectral output of the FFT or DFT routines. Windowing routines accomplish this by forcing the beginning and end of any sequence to approach each other in value. Since they must work with any sequence they force the beginning and ending samples near zero. To make up for this reduction in power, windowing routines give extra weight to the values near the middle of the sequence. The difference between windows is the way in which they transition from the low weights near the edges to the higher weights neqr the middle of the sequence. Signal-to-noise ratio(SNR) can be determined by the ratio of the output noisy signal variance to the input noisy signal variance of a window. Standard deviation of noise is reduced by windowing. Thus, the windowing operation improved the SNR of the noisy signal. This paper shows a performance estimation of windowing on a single tone with added Gaussian noise and uniform noise.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.475-480
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• 2023

When modeling a sensor system mathematically, we assume that the sensor noise is Gaussian and white to simplify the model. If this assumption fails, the performance of the sensor model-based controller or estimator degrades due to incorrect modeling. In practice, non-Gaussian or non-white noise sources often arise in many digital sensor systems. Additionally, the noise parameters of the sensor model are not known in advance without additional noise statistical information. Moreover, disturbances or high nonlinearities often cause unknown sensor modeling errors. To estimate the uncertain noise and model parameters of a sensor system, this paper proposes an iterative batch calibration method using data-driven machine learning. Our simulation results validate the calibration performance of the proposed approach.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2597-2602
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• 2007

In this paper, the performance analysis is experimentally carried out in order to select the best cooling fan and shroud considering both cooling performance and noise reduction. 4 cooling fans have been tested in the fan tester and the real excavator. In order to obtain the performance of the cooling fans, flow capacity has been estimated by measuring flow velocity using a hot wire anemometer, and noise radiation has been also measured to estimate the fan noise. Characteristics of a box-type and a streamlined shroud have been examined by changing the immersion depth of cooling fans. Based upon the results, the best cooling fan is selected. Finally, the criterion to select the best cooling fan has been set up.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.647-653
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• 2009

Taguchi parameter design is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used SN (Signal to Noise) ratio to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. This paper describes the prediction technique of vehicle performance using parameter analysis to reduce man hour and test development period as well as to achieve stable NVH performance. Design engineer could efficiently decide the design variable using parameter analysis database in early design stage. These improvements can reduce the time needed to develop better vehicles.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.76-80
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• 1992

We consider the tapped-delay line (TDL) equalizer with the few calculation quantity and the simplity, the decision feedback equalizer (DFE) with the good property for interference, and lattice equalizer(LE) with high insensitivity to roundoff noise in mobile communication fading channel. The used adaptive algorithm is the LMS algorithm and RLS algorithm. In this paper, we have evaluated the performance of the TDL equalizer, the decision feedback equalizer, and lattice-structured equalizer, for the digital signal corrupted by the impulsive noise and the white gaussian noise under the fading channel environment. From the results of error performance analysis, it is confirmed that lattice-structured equalizer has better performance than DFE equalizer and TDL equalizer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.30-35
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• 2007

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, test equipment composed of fan, duct and silencer was set up. Using the test equipment, insertion loss tests were carried out to improve the performance in the low-frequency ranges. Through a series of tests, the fact that array resonators may be effective in the low-frequency noise has been verified. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer were proposed and its high acoustic performance in the low-frequency range has also been verified.