• 한국전산유체공학회:학술대회논문집
• /
• 2006.05a
• /
• pp.57-60
• /
• 2006

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.12
• /
• pp.962-968
• /
• 2014

The lattice Boltzmann method(LBM) has attracted attention as an alternative numerical algorithm for solving fluid mechanics since the end of the 90's. In these days, its intrinsic unsteadiness and rapid increase in computing power make the LBM be more applicable for computing flow-induced noise as well as fluid dynamics. The lattice Boltzmann method is a weakly compressible scheme, so we can get information about both aerodynamics and aeroacoustics from single simulation. In this paper, numerical analysis on Aeolian tone noise generated by tandem-twin square cylinders in duct is performed using the LBM. For simplicity, laminar two-dimensional fluid models are used. To verify the validity and accuracy of the current numerical techniques, numerical results for the laminar duct and the cylinder flows are compared with the analytical solution and the measurement, respectively. Then, aerodynamic noise of the twin tandem square cylinders is investigated. It is shown that the aerodynamic noise from the twin tandem square cylinders can be reduced by controlling the distance between the cylinders.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.3
• /
• pp.239-245
• /
• 2016

Deramping technique has been widely used to acquire high resolution SAR(Synthetic Aperture Radar) images for the advantage of the data size and the processing time. However, unwanted spurious signals caused by SAR hardware can be leaked in the process of converting into a digital signal through the ADC(Analog-Digital Converter) and added in a echo signal. These tones make image quality degrade significantly. In order to solve this problem, the unwanted tones need to be detected by analysing the characteristic of the noise tone and then effectively removed from raw data. In this paper, we propose a method for efficiently removing noise tone on the raw data based on the characteristic of spurious signals.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.2
• /
• pp.105-110
• /
• 2004

The objective of this study is to obtain the instability characteristics of the plane jet impinging on circular cylinder associated with the cylinder-tone. It is found that the characteristics depends upon he ratio of the cylinder diameter to the nozzle width, D/h, and the jet velocity. When the ratio is oderate the cylinder-tone is similar to the edge-tone. With increase of the ratio, its characteristics ecomes similar to that of the plate-tone in which only the high-speed tone associated with turbulent et is generated. When D/h 〈1. the frequency range, especially the lower limit of frequency, is ignificantly influenced by the cylinder diameter. At around D/h = 1/2, while low speed tones are nduced with the antisymmetric mode of instability and affected by the vortex shedding from the ylinder, high-speed tones are generated, at first, with the symmetric mode of instability. and then, ith antisymmetric mode, as the jet velocity increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.71-74
• /
• 2012

Generally, tone noise is generated at the rotary wing and helicopter. BVI(Blade-Vortex Interaction) noise is one of the helicopter's tone noise. The BVI noise is governed by tip-vortex characteristics such as vortex size, strength and trajectory. To avoid BVI, many methods have been developed and proposed. In this paper, rotating blade with active tab was numerically investigated to reduce BVI noise. For flow and noise simulation, the lifting surface approach and the acoustic analogy were used. Using numerical methods, the noise directivity and maximum noise position were predicted.

• Proceedings of the IEEK Conference
• /
• 2003.11a
• /
• pp.61-64
• /
• 2003

In this paper, we implement PAMD(Positive Answering Machine Detection) for discrimination human and ARS. We are used Grunt detection, Glitch Noise detection and Tone detection for PAMD. It distinguishes voice signals from ring-back tone and glitch noise respectively. And as a second step, it judges whether human responses or ARS responses after integrating pattern changes like initial response period, the number of voice data, each time of voice data period and glitch noise. The accuracy is about 9375 in ASR and about 98％ in Mobile phone.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.1406-1412
• /
• 2001

Roof racks have become a very popular feature of vehicles as the market demand for SUV's and RV's has increased drastically over the years. Aeolian tone from the cross bars however. could be a source of severe discomfort for the passengers. Both experimental and numerical steps are taken to enhance the understanding of the generation mechanism of the wind noise. A successful reduction of the noise is achieved by imposing asymmetry in the section geometry, which reduces the strength of Karmann vortices shed downstream.

• Journal of the Korean Society of Visualization
• /
• v.9 no.4
• /
• pp.35-40
• /
• 2011

An experimental investigation of the characteristic of non-premixed lifted flames with nozzle hole-tone of high-frequency has been performed. Before the fuel was supplied to nozzle, the fuel was supplied through a burner cavity which was located under the nozzle. The fuel passed through the excitation cavity under the influence of the high-frequency affects the lifted flame characteristics. The measurements were performed in flow range that occurs lifted flame and blow out. When the high-frequency is generated from burner cavity, the lifted length became shorter, and noise reduced comparing to unexcitation case. Additionally, operating flow range was increased and diameter of flame base became smaller with high-frequency effect. Through this experiments, it's ascertained that the high-frequency excitation can be adopted with effective method for flame stability and noise reduction.

• Journal of the Optical Society of Korea
• /
• v.18 no.5
• /
• pp.594-597
• /
• 2014

We propose a novel approach to measure the residual phase noise (RPN) of a photodiode (PD) based on a two-tone correlation method. Compared with the previous measurements of the RPNs of PDs, this method is more convenient in practical application. In this method, two microwave sources and other components were placed in two isolated links sharing the same PD, so the noises of them were uncorrelated. With an FFT analyzer, the uncorrelated noises could be mostly suppressed while only the RPN of the PD was preserved. Voltage-dependent nonlinearities of PDs were studied previously. In this letter, we investigate the relationship between the RPN of the PD and the bias voltage on the PD. By changing the bias voltage, the difference of the RPN can be up to 10 dB.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.1
• /
• pp.159-166
• /
• 1999

In this paper, we examined noise figure and the 3rd order intercept point in sensitivity single tone desensitization, and response attenuation by intermodulation spurious of receiver and also analyzed them through simulation based on J-STD-0.18, which is the minimum specification of PCS mobile station. The result of simulation was as follows ; In sensitivity specification, the total noise figure was 5.99dB and the 3rd order intercept point was -33.979dB. Ins ingle tone desensitization and intermodulation spurious response attenuation specification, the total noise figure was 6.375dB and the 3rd order intercept point was -26.99dBm. When there is an interference tone, the nosie figure and the 3rd order intercept point have been increasedly 0.367dB respectively, compared wit that of no interference tone. Because the amount of increase in the 3rd order intercept point was highly raised more than that of noise figure, mixer, closely related to interference tone should be specified in high 3rd order intercept point. At a frequency spacing of 1.25MHz and 2.05MHz from center frequency in IF SAW filter, attenuation should be more than 45dB.