• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.11a
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• pp.26-29
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• 2022

The diffuse sound field plays a crucial role in the perceptual quality of the auralization of virtual scenes. Diffuse Rain is a geometrical scattering model which enables the simulation of diffuse fields that is compatible with acoustic ray tracing, but is often computationally expensive. We develop a novel method that can reduce this cost by rendering the large number of Diffuse Rain data in Ambisonics format. The proposed method is evaluated in a shoebox scene simulation run on MATLAB, in reference to a more faithful method of rendering the Diffuse Rain data ray-by-ray. The EDC and IACC of the binaural output show that the simulated diffuse field can be rendered in Ambisonics with only minimal deviations in energy decay and spatial quality, even with 1^st-order Ambisonics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.61-64
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• 2007

This study is dealt with a method to enhance low-frequency diffuse sound field in a scaled reverberation chamber. Because scaled reverberation chamber has not enough room volume, as a result, it shows a few room modes. So it is not build up low-frequency diffuse sound field. A Helmholtz resonator's arrangement is used to improve spatial uniformity of sound pressure at low frequency. The spatial distribution of sound field has been measured before and after control. The standard deviation of sound field has decreased at 315Hz 1/3 Octave band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1002-1006
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• 2000

It is diffuse sound field that measuring condition of absorption ratio and sound transmission loss for material consist of building are measured in reverberartion room and on-site. In this study, for upkeeping diffuse sound field in reverberation room, it is measured and etimated that sound field is effected according to sound source lacation and characteristics of emission directivity for sound source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.643-649
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• 1998

This paper is to compare the absorption coefficient with normal incidence waves and it with diffuse incidence waves of glass wool which the most used absorption material and multi layer fiber. The absorption coefficient with normal incidence waves is calculated by surface impedance that measured by using an acoustic tube. Based on this data, the absorption. coefficient with diffuse incidence waves is predicted and is compared with measured the absorption coefficient in reverberation room.

• Journal of KSNVE
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• v.7 no.6
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• pp.945-952
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• 1997

This paper shows the feasibility of the suggestion that the angle distribution of incident sound to panels might be gaussian, instead of the conventional uniform distribution in the analysis of transmission loss of panels. To prove the suggestion, the problems with the diffuse sound field in a reverberation room are examined by case studies and the comparision of the prediction with the measurement of sound transmission loss of walls are performed. The results of the comparision show good agreement between the two values.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.507-518
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• 2012

It is now widely accepted that the resulting displacement field within elastic, inhomogeneous, anisotropic solids subjected to equipartitioned, uniform illumination from uncorrelated sources, has intensities that follow diffusion-like equations. Typically, coda waves are invoked to illustrate this concept. These waves arrive later as a consequence of multiple scattering and appear at "the tail" (coda, in Latin) of seismograms and are usually considered an example of diffuse field. It has been demonstrated that the average correlations of motions within a diffuse field, in frequency domain, is proportional to the imaginary part of Green's function tensor. If only one station is available, the average autocorrelation is equal to the average squared amplitudes or the average power spectrum and this gives the Green's function at the source itself. Several works address this point from theoretical and experimental point of view. However, a complete and explicit analytical description is lacking. In this work we study analytically some properties of the Green's function, specifically the imaginary part of Green's function for 2D antiplane problems. This choice is guided by the fact that these scalar problems have a closed analytical solution (Kausel 2006). We assume the diffusiveness of the field and explore its analytical consequences.

• Smart Media Journal
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• v.8 no.2
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• pp.16-20
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• 2019

Fast Fourier Transform in the vibration acceleration analysis system has recently been utilized in the field of sensor measurement. In this paper, we propose a Fast Fourier Transform based method of detecting the normal frequency among the many frequency types of diffuse field. This normal frequency is expressed by the formula of frequency damping recognition which is calculated in a similar way to the octave center frequency. Based on this theory, this paper can more accurately inform noise producers of the degree of damping, which is different from the vibration type of diffuse field.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.394-400
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• 2018

Various numerical methods have been adopted for indoor noise assessments of ship plant. Acoustical radiosity method is one of the high frequency approaches for acoustic field analysis, which assumes diffuse reflections by boundaries so that it could be efficiently applied to the acoustically diffused indoor space noise analysis. In this study, an acoustic field analysis program has been developed based on radiosity method, which could apply for acoustically large enclosures such as ship's indoor space. For this purpose, the procedure of the acoustical radiosity method has been summarized and implemented to an acoustic field analysis program using MATLAB. Numerical example for a rectangular indoor space has investigated validity of the implemented program. Steady state sound pressure levels calculated for a continuous acoustic source signal have shown good agreement with those by other solutions such as an analytic solution and a ray tracing method. Instantaneous sound pressure levels calculated for an impulsive acoustic signal have provided the clues of direct/reflected acoustic field and reverberation time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.973-981
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• 2013

The main role of an acoustic diffuser is to diffuse reflected sound field spatially. Since the pioneering work of Schroeder, there have been investigations to improve its performance by using shape/sizing optimization methods. In this paper, a gradient-based topology optimization algorithm is newly presented to find the optimal distribution of reflecting materials for maximizing diffuser performance. Time-harmonic acoustic analysis in a two-dimensional acoustic domain is carried out where the domain is discretized by finite elements. Perfectly matched layers are placed to surround the domain to simulate non-reflecting boundary conditions. Design variables are assigned to each element of which material properties are interpolated between those of air and those of a rigid body. An approach to extract the reflected field from the total acoustic field is employed. To validate the effectiveness of the proposed method, design problems are solved at different frequencies. The performance of the optimized diffusers obtained by the proposed method is compared against that of the conventional Schroeder diffusers.

• The Bulletin of The Korean Astronomical Society
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• v.22
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• pp.34-34
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• 1997