• The Journal of the Acoustical Society of Korea
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• v.22 no.6
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• pp.472-481
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• 2003

Low-frequency hi-static reverberation model (LHYREV-B, Low-frequency Hanyang univ. Reverberation model-Bistatic) based on the parabolic approximation for shallow water environment is presented. In this paper bistatic reverberation level is computed using the angle-independent scattering strength function and the wave-based acoustic model. The signal simulated by the LHYREV-B model is compared with the observed signals and it is shown that the LHYREV-B model provides a closer fit to the observed signals.

• The Journal of the Acoustical Society of Korea
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• v.25 no.8
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• pp.389-394
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• 2006

Mid-Frequency bistatic reverberation level is modeled using ray theoretic algorithms. The algorithm assumes multiple forward/backward scatter along with reciprocity in the Propagation paths. The environments modeled are assumed to be range independent in bathymetry, bottom scattering and surface scattering. Mid-Frequency bistatic scattering algorithm is used as a scattering model. A comparison of predicted reverberation versus time with measured data is presented to verify the bistatic reverberation model. The result demonstrates that it is possible to obtain reasonable reverberation Predictions in experimental site.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.58-65
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• 2001

Recently, a 5-degrees-of-freedom (DOF) reverberation model was proposed as a method of representing subjective perception of reverberation as objective measures[1]. This model approximates sound energy decay curve by five objective measures, widely used in which have been concert hall acoustics. However, it is note worthy that there can be infinite number of impulse responses which correspond to a selected 5-DOF reverberation model. There may exist some filters making very unnatural and unrealistic sound. In this paper, the limitation of the 5-DOF reverberation model when it is used as a filter design criteria is investigated. When a 5-DOF reverberation model is given, additional constraints to get natural reverberation are suggested. This is based on the listening tests for several quite different source sounds.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.96-105
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• 2019

Ocean reverberation is the most limiting factor in designing realistic and real-time system for sonar simulator. The simulation for an ocean reverberation requires a lot of computational loads, so it is hard to embed program and generate real-time signal in the sonar simulator. In this study, we simulate a time-domain bottom reverberation signal based on Harrison's energy-flux bottom reverberation model by applying Doppler effects as ship maneuvering and autoregressive model. Finally, the bottom reverberation signal with realistic characteristics could be generated for the simulation of ONR reverberation modeling workshop-I problem XI and East Sea ocean environments.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.740-754
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• 2009

Sound in the ocean is scattered by inhomogeneities of many different kinds, such as the sea surface, the sea bottom, or the randomly distributed bubble layer and school of fish. The total sum of the scattered signals from these scatterers is called reverberation. In order to simulate the reverberation signal precisely, combination of a propagation model with proper scattering models, corresponding to each scattering mechanism, is required. In this article, we develop a reverberation model based on the ray theory easily combined with the existing scattering models. Developed reverberation model uses (1) Chapman-Harris empirical formula and APL-UW model/SSA model for the sea surface scattering. For the sea bottom scattering, it uses (2) Lambert's law and APL-UW model/SSA model. To verify our developed reverberation model, we compare our results with those in Ellis' article and 2006 reverberation workshop. This verified reverberation model SNURM is used to simulate reverberation signal for the neighboring seas of South Korea at mid frequency and the results from model are compared with experimental data in time domain. Through comparison between experiment data and model results, the features of reverberation signal dependent on environment of each sea is investigated and this analysis leads us to select an appropriate scattering function for each area of interest.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.671-678
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• 2002

High-frequency monostatic reverberation model (HYREV: HanYang Univ. REVerberation model) suitable for shallow-water environment is presented. It is difficult to predict reverberation signals in shallow water due to scattering from sea surface and seafloor. The arrival times and transmission losses from the source to scatterers are obtained from the eigenrays. The composite roughness theory is used to predict the boundary scattering. The signals generated by the HYREV and the GSM were compared with the observed signals and it is showed that the HYREV model provided a closer fit to the observed signals than those obtained using the GSM.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.679-685
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• 2002

Low-frequency mono-static reverberation model for shallow-water environment is presented. It is necessary to develop the transmission loss model to calculate the sub-bottom interaction because the ray-based transmission loss model is difficult to compute the pressure accurately which penetrates the bottom medium. In this paper reverberation level is calculated using the RAM (Range dependent Acoustic Model) to augment the multi-path expansion model because it does not estimate transmission loss accurately in shallow water. The signals generated by the L-HYREV and the GSM are compared with the observed signals and it is showed that the L-HYREV model provides a closer fit to the observed signals than those obtained using the GSM.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.48-53
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• 2000

To analyze a room reverberation, many objective parameters have been suggested as measures of subjective perception in concert hall acoustics. However, it is difficult to understand the relationship among the individual parameters and to have a whole image of them. In this paper five primary objective parameters were selected and a reverberation model based on them was established by the reverberation decay curve. The proposed model was interpreted geometrically in terms of subjective characteristics. And finally we discuss the usefulness and the limitation of the model when it is applied to the analysis and.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.3
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• pp.384-390
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• 2020

The reverberation effect on the sound when producing movies or VR contents is a very important factor in the realism and liveliness. The reverberation time depending the space is recommended in a standard called RT60(Reverberation Time 60 dB). In this paper, we propose a scene recognition technique for automatic reverberation editing. To this end, we devised a classification model that independently trains color images and predicted depth images in the same model. Indoor scene classification is limited only by training color information because of the similarity of internal structure. Deep learning based depth information extraction technology is used to use spatial depth information. Based on RT60, 10 scene classes were constructed and model training and evaluation were conducted. Finally, the proposed SCR + DNet (Scene Classification for Reverb + Depth Net) classifier achieves higher performance than conventional CNN classifiers with 92.4% accuracy.

• Journal of electromagnetic engineering and science
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• v.13 no.3
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• pp.192-194
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• 2013

This paper proposes a validation model using a reverberation chamber for verification of the effectiveness and accuracy of the statistical power balance (PWB) method. The PWB method treats electromagnetic (EM) field distributions in certain environments as a representative value of an "ensemble" average, so a reverberation chamber is utilized as a testing apparatus to experimentally simulate the sets of measurement field "ensemble" inside a complex environment. Measurements are performed with various test conditions for environmental loss using flat absorbers, and front and side doors of the chamber. Comparison between the PWB analysis and the measurement results shows good agreement, indicating the usefulness of this statistical analysis method for stating the electromagnetic field inside the EM zone as a representative value to general structures.