• Journal of Environmental Science International
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• v.25 no.10
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• pp.1407-1415
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• 2016

In this study, we investigated the relationship between noise reduction and the community structure of nine groups of typical plant communities as well as the reduction in noise at different frequencies. The semantic differential method was adopted to explore the perception of noise reduction. The results indicated that there was a significantly positive correlation between noise reduction and coverage, a significantly negative correlation between noise reduction and bifurcate height, and a negative correlation between noise reduction and bare rate. However, there was no significant correlation between noise reduction and height, diameter at breast height, or crown width. The reduction of middle-frequency noise was better than that of low- and high-frequency noise. The indicators "quiet" and "calm" showed that plant communities could reduce the noise perceived by humans. However, overly dense woodland caused nervousness, fear, depression, and other negative effects. Relatively open environments and those with large forest gaps obtained the highest evaluation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.1
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• pp.28-34
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• 2014

This study provides the numerical finite-element method(FEM) estimating the friction noise induced by the negative slope in the friction-velocity curve. The friction noise due to the friction-velocity curve is experimentally investigated through the pin-on-disk setup. The measured squeal frequency is estimated by FEM. The friction curve is measured by the friction test, then it is applied to the complex eigenvalue analysis. The results shows that the experimental squeal frequency can be determined by the FEM analysis. Also, it is emphasized that the negative friction-velocity slope is essential in generating friction noise in the pin-on-disc system.

• International journal of advanced smart convergence
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• v.9 no.2
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• pp.20-27
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• 2020

Sound event detection in real-world environments suffers from the interference of non-stationary and time-varying noise. This paper presents an adaptive noise reduction method for sound event detection based on non-negative matrix factorization (NMF). In this paper, we proposed a deep learning model that integrates Convolution Neural Network (CNN) with Non-Negative Matrix Factorization (NMF). To improve the separation quality of the NMF, it includes noise update technique that learns and adapts the characteristics of the current noise in real time. The noise update technique analyzes the sparsity and activity of the noise bias at the present time and decides the update training based on the noise candidate group obtained every frame in the previous noise reduction stage. Noise bias ranks selected as candidates for update training are updated in real time with discrimination NMF training. This NMF was applied to CNN and Hidden Markov Model(HMM) to achieve improvement for performance of sound event detection. Since CNN has a more obvious performance improvement effect, it can be widely used in sound source based CNN algorithm.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.167-172
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• 2023

A low-noise phase-locked loop(PLL) with three negative feedback loops has been proposed. It is not easy to improve noise characteristics with a conventional PLL. The added negative feedback loops reduce the input voltage magnitude of voltage controlled oscillator which determines the jitter characteristics, enabling the improvement of noise characteristics. Simulation results show that the jitter characteristics are improved as a negative feedback loop is added. In the case of power consumption, it slightly rises by about 10%, but jitter characteristics are improved by about two times. The proposed PLL was simulated with Hspice using a 1.8V 180nm CMOS process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.681-686
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• 2015

The onset characteristics of friction-induced noise for a steel plate and 4 metallic pins (Cu, Ni, Al, Mg) were studied through the pin-on-disk machine and the reciprocating testing machine. The results showed that the negative slope of the friction curve was related to the onset time of friction noise. Particularly, Cu was found to be the best metallic material for preventing squeak noise in terms of the onset time and the negative friction slope.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.638-648
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• 2003

An active capacitance circuit is analyzed in depth and its application to active RF BPF with low noise figure is discussed. The characteristics of the active capacitance circuit made of FET[1] exhibits negative resistance and conventional capacitance, which is easily controlled. However, it is difficult to make the negative resistance adequate in the designated frequency range due to the lack of detailed analysis, which could make an active circuit unstable as the frequency is going higher or lower. In this paper, we analyzed the negative resistance characteristics of active capacitance circuits and also presented the method that the flatness of passband can be controlled. Finally we have designed a 4-stage active BPE, which results in bandwidth of 100 MHz, 0,04 dB insertion loss, 0.2 dB ripple, and noise figure of 2.4 dB at 1.75 GHz band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.624-629
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• 2003

In this paper, broadband shunt technique for increasing transmission loss is experimentally investigated. Piezoelectric shunt damping is studied using resonant shunt circuit and negative capacitor shunt circuit. A resonant shunt circuit is implemented by using a resistor and inductor. Negative Capacitor shunt damping is similar in nature to resonant shunt damping techniques, as a single piezoelectric material is used to dampen multi-mode. Performance of both methods is experimentally studied for noise reduction. This is based upon SAE J1400 test method and a transmission loss measurement system is provided for it. This paper will present the test setup fer transmission loss measurement and the tuning procedure of shunt circuits. Finally the results of sound transmission tests will be shown.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.423-430
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• 2013

The characteristics of friction noise due to the friction-velocity curve is experimentally investigated through the pin-on-disk setup. The rotation speed of the disk is controlled in order to produce the sliding speed variation. Then, the friction coefficient and the corresponding friction noise are simultaneously measured with respect to the sliding speed between the steel disk and aluminum pin. The experimental results show that the negative friction-velocity slope is essential in generating friction noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.29-32
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• 2005

This paper presents experimental analysis of a friction-driven wheel that is responsible for wheel squeal. Squeal noise generating mechanism and environment of train u heels has been tried to reproduce under laboratory condition. Scale down size rail and wheel are made and influential parameters to squeal noise are measured, e. g. frictional force, pressure between rail and wheel, creep speed of rail. Negative damping characteristic curve are calculated currently. Necessary relating computational analysis is also carried on.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.590-598
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• 2004

An active capacitance circuit which employs series feedback network for the implement of negative resistance and low noise operation is analyzed in depth and its application to low noise active RF BPF's is discussed. Whereas many authors reported a lot of circuits that embody negative resistance circuit most of them have concerns for the equivalent resistance and reactance value at the center frequency. In this case, it could be possible to face a problem that the negative resistance circuit becomes unstable, or have poor flatness in passband because of insufficient forecast for the negative resistance values as the frequency goes higher or lower. In this paper, we extracted the exact equivalent values of this circuit and analyzed the RF characteristics with the varying the values of active devices and feedback circuits and presented the method that the flatness of passband can be improved. We have designed a 4-pole active BPF, which has the bandwidth of 60 ㎒, 0.67 ㏈ insertion loss, 0.3 ㏈ ripple, and noise figure of 3.0 ㏈ at 1.99 ㎓ band.