• The Journal of Natural Sciences
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• v.8 no.2
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• pp.101-109
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• 1996

In this paper, using the derived formula based on field theory both geometrical optics and diffraction theory, several features of same buildings of Bertoni's construction that influence the propagation of signals between antennas located on the same floor have been investigated theoretically and compared with previously studied results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.635-644
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• 2005

This paper is. a study on relation between road traffic noise(RTN) and sound power level(PWL). At present, many experimental formulae and prediction formulae are used for prediction of RTN. But these formulae are difficult to appiy to the metropolitan area because these formulae are inaccurate in the different condition from reference condition. This paper calculate RTN and PWL of each prediction formula, choose the best one and make a noise map of the subject area. Procedure is as follows. First, calculate $L_{eq}$ of RTN using experimental formulae and prediction formulae. Second, calculate PWL using $L_{eq}$ of RTN and distance attenuation for point source at semi-free field. Third, choose the most accurate formula. And finally, make a noise map of the subject area at present and future. The result using noise map will be able to apply to application field. Noise mapping tool used on this paper is Raynoise program using Ray Tracing Method(RTM), Mirror Image Source Method(MISM) and Hybrid Method(HM).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.934-938
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• 2008

To customize individual characteristics of HRTF, a spherical model has been used for structural modeling technique. A pseudo-code of prolate spheroidal HRTF caused by incident acoustic point source is already developed, and it can be used a head shadow filter for structural modeling of HRTF. In this research, to see the necessity and efficiency of spheroidal head modeling, ITD optimization is performed on CIPIC HRTF database. From given cost function, ITD-optimized spheroidal head model, whose ITD information is the most matched version of measured ITD information, is found by varying head parameters subject by subject. By comparing results of ITD-optimized spheroids and ITD-optimized spheres, we concluded that a spherical head model is more efficient way of generating head shadow effect than a spheroidal head model does.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.725-733
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• 2010

A simulator is proposed in this paper for predicting the RF signal level after propagating over sea and land surfaces. Various sea and land types and transmit/receive antenna patterns, as well as the locus of the transmit antenna, are considered for this simulator. At first, microwave reflection characteristics of various sea surfaces have been computed, based on an empirical formula which is developed in this study for the relation between the sea surface roughness and wind speed. Then, microwave reflections from land surfaces such as forests, agricultural areas, and bare surfaces, are computed using the first-order vector radiative transfer theory. Finally, the signal paths over sea and land surfaces are found using the ray tracing technique and the digital elevation model, and the signal level received by a receiving antenna is computed by the using the reflection coefficients of sea and land surfaces and the signal paths.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.19-25
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• 2007

We studied prism design method for actual light source that have bulk in order to accomplish particular intensity distribution. When we know incidence angle and try to send ray to given direction, numerical formula that yields prism vertical angle, and then vertical angles were calculated sequentially. After analyzing problem that supposing to point light source, supplemented this and derived applicable prism design method on bulk light source. The intensity distribution and efficiency that came out by each design results were compared and analyzed, we got improved results through supplemented design method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.641-644
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• 2005

This study reveals some recent attempt in modeling empirically obtained B&K HATS (Head and Torso Simulator) HRTFs (Head Related Transfer Functions) to Isolate parameters that stimulate lateral and elevation perception. Localization using non-individual HRTFs often yields poor performance in synthesizing virtual sound sources when applied to a group of individuals due to differences in size and shape of head, pinnae, and torso. For realization of both effective and efficient virtual audio it is necessary to develop a method to tailor a given set of non-individual HRTFs to fit each listener without measuring his/her HRTF set. Pole-zero modeling is applied to fit HRIRs (Head Related Impulse Responses) and modeling criterions for determining suitable number of parameters are suggested for efficient modeling. Horizontal HRTFs are modeled as minimum-phase transfer functions with appropriate ITDs (Interaural Time Delay) obtained from RTF (Ray Tracing Formula) to better fit the size of listener's head for usage in simple virtualizer algorithms without complex regularization processes. Result of modeling HRTFs in the median plane is shown and parameters responsible for elevation perception are isolated which can be referred to in the future study of developing customizable HRTFs.