• ETRI Journal
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• 제32권6호
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• pp.837-842
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• 2010

This paper proposes robust source localization methods for estimating the azimuth angle, elevation angle, velocity, and range using a low-complexity planar antenna array in impulsive non-Gaussian noise environments. The proposed robust source localization methods for wireless communication applications are based on nonlinear M-estimation provided from Huber and Hampel. Simulation results show the robustness performance of the proposed robust methods in impulsive non-Gaussian noise.

• Ocean and Polar Research
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• 제34권3호
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• pp.287-296
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• 2012

In the theory of source-driven abyssal circulation, the forcing is usually assumed to be steady source (deep-water formation). In many cases, however, the deep-water formation occurs instantaneously and it is not clear whether the theory can be applied well in this case. An attempt is made to resolve this problem by using a simple reduced gravity model. The model basin has large depth change compared for its size, like the East Sea, such that isobaths nearly coincide with geostrophic contours. Deep-water is formed every year impulsively and flows into the model basin through the boundary. It is found that the circulation driven by the impulsive source is generally the same as that driven by a steady source except that the former has a seasonal fluctuation associated with unsteadiness of forcing. The magnitudes of both the annual average and seasonal fluctuations increase with the rate of deep-water formation. The problem can be approximated to that of linear diffusion of momentum with boundary flux, which well demonstrates the essential feature of abyssal circulation spun-up by periodic impulsive source. Although the model greatly idealizes the real situation, it suggests that abyssal circulation can be driven by a periodic impulsive source in the East Sea.

• 한국소음진동공학회논문집
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• 제14권9호
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• pp.877-883
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• 2004

This paper addresses the way in which we can find where impulsive noise sources are. Specifically, we have an interest in the case that the signal is embedded in noise. We propose a signal processing method that can identify impulsive sources' location. The method is robust with respect to spatially distributed noise. This has been achieved by the modified beamforming method with regard to cepstrum domain is used. It is noteworthy that the cepstrum has the ability to detect periodic pulse signal in noise. Numerical simulation and experiments are performed to verify the method. Results show that the proposed technique is quite powerful for localizing the faults in noisy environments. The method also required less microphones than conventional beamforming method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.713-717
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• 2014

This paper presents a beamforming technique for locating impulsive sound source. The conventional frequency-domain beamformer is advantageous for localizing noise sources for a certain frequency band of concern, but the existence of many frequency components in the wide-band spectrum of impulsive noise makes the beamforming image less clear. In contrast to a frequency-domain beamformer, it has been reported that a time-domain beamformer can be better suited for transient signals. Although both frequency- and time-domain beamformers produce the same result for the beamforming power, which is defined as the RMS value of its output, we can use alternative directional estimators such as the peak value and crest factor to enhance the performance of a time-domain beamformer. In this study, the performance of three different directional estimators, the peak, crest factor and RMS output values, are investigated and compared with the incoherent interfering noise embedded in multiple microphone signals. The proposed formula is verified via experiments in an anechoic chamber using a uniformly spaced linear array. The results show that the peak estimation of beamformer output determines the location with better spatial resolution and a lower side lobe level than crest factor and RMS estimation in noise free condition, but it is possible to accurately estimate the direction of the impulsive sound source using crest factor estimation in noisy environment with stationary interfering noise.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.903-912
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• 2007

Faults of rotating parts of a train normally generate unexpected frequency band or impulsive sound[1] which has a period when it moves with a constant speed. The former can be detected by the moving frame acoustic holography method, which visualizes sound field that is generated by a moving and emitting pure tone or band limited noise source. We have attempted to apply the method to the latter case: the periodic impulsive sound which generate different signal compared with what can be measured by the band limited noise. The signal to noise ratio which determines the success of early fault detection must also be studied with the impulsive and moving signal. This research shows how the problems related with these issues can be resolved. The main idea is that periodic impulsive signal can be expressed by infinite set of discrete pure tones. This enables us to obtain lots of holograms that visualize periodic impulsive sound field including noise by using the moving frame acoustic holography method. Therefore holograms can be averaged to improve the signal to noise ratio until having reliable information that exhibits where the impulsive sources are. Theory and experiment by using the miniature vehicle are described [Work supported by BK21 & KRRI].

• 한국자동차공학회논문집
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• 제14권4호
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• pp.139-148
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• 2006

Valve train is one of the important noise sources in idling engines. Valve train noise comes mostly from two different impacts. One is the impact between cam and tappet at the beginning of the valve open period, which is an important source of impulsive noise of valve trains. The other is the impact between valve and valve seat at the closing of the valve open period. In case of mechanical lash adjusters, it is very difficult to control the initial impact. In this paper, we designed various types of cam profiles, especially in the opening ramp design, and investigated the effect of cam profiles on the magnitude of the initial impact. The effects that some cam design parameters have on the impulsive noise are also observed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1191-1196
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• 2007

This research presents a laboratory study about an annoyance of impulsive sound caused by construction site(breaker and blasting). The sources are sampled from outdoor noise and their levels range from 40 to 75 dB at the interval of 5dB. The noise unit is based on A-weighted sound exposure level (ASEL; $L_{AE}$). To make equal ASEL of outdoor noise, finite impulse response (FIR) filter is applied to the originally sampled source to include the effect of distance attenuation. The evaluation method of jury test adopted a Semantic Difference Method (SDM). In the result of the Jury test for impulsive noise, the annoyance response of blasting noise was higher than that of breaker noise.

• 한국컴퓨터정보학회논문지
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• 제19권5호
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• pp.37-42
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• 2014

본 연구의 목적은 170 dB 수준의 충격 소음원에서 주파수별 귀마개의 차음성능을 확인하고, 주파수 특성과 패턴 형상을 분석하는데 있다. 충격 소음에서의 Combat Arm Earplug와 3M Form types 1100 Earplug의 주파수별 귀마개 차음성능을 산출하였다. 차음성능을 확인하기 위해서 B&K Head and Torso Simulator와 Ear Simulator를 제작하여 충격 소음원의 주파수별로 차음성능을 비교하였다. 기존의 연구들은 충격 소음원이라 할지라도 대부분 140 dB 수준의 고충격 소음원이였으나, 본 연구는 그보다 더 높은 수준의 충격 소음원이라는 특징을 가지고 있다. 연구결과, 주파수별 충격소음의 차음효과는 평균 28.58 dB 인 것으로 나타났다.

• 한국생활과학회지
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• 제17권3호
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• pp.485-492
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• 2008

The study is to provide the types of fashion consumption of male and female university students and to analyze fashion involvement to the types and students' source of fashion information. Then the correlations were examined between fashion involvement and source of fashion information. The data were analyzed by a factor analysis, one-way ANOVA, Duncan test, cluster analysis, cross-tabulation analysis. The results are as follows: 1. The awareness about fashion consumption is classified into five factors: "hedonic consumption", "impulsive consumption", "brand loyal consumption", "prudent consumption", and "independent consumption". The fashion involvement to the types is categorized into four factors; "pleasure", "trend", "image", and "risk awareness". The source of fashion information is categorized into "mass media", "product information", and "personal information". 2. The fashion consumption is classified into three types: "an independent consumer type", "a brand loyal/ prudent consumer type", and "an impulsive consumer type". 3. In the fashion involvement to the types and the source of fashion information, there is a high correlation between the factors of "mass media" and "trend", "product information" and "pleasure" and "personal information" and "trend".

• Interaction and multiscale mechanics
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• 제6권3호
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• pp.287-300
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• 2013

In this paper, the effect of impulsive line on the propagation of shear waves in non-homogeneous elastic layer is investigated. The rigidity and density in the intermediate layer is assumed to vary quadratic as functions of depth. The dispersion equation is obtained by using the Fourier transform and Green's function technique. The study ends with the mathematical calculations for transmitted wave in the layer. These equations are in complete agreement with the classical results when the non-homogeneity parameters are neglected. Various curves are plotted to show the effects of non-homogeneities on shear waves in the intermediate layer.