• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.451-454
• /
• 2002

HYREV (Hanyang univ. Reverberation model)은 천해에서 적용 가능한 고주파 단상태 잔향음 모델이다. 천해에서 발생하는 잔향음은 외해에 비해 경계면 산란 영향이 크기 때문에 경계면 산란 영향을 정확히 포함한 잔향음 모델 개발이 필요하다. 본 모델에서는 고유음선(eigenray) 계산을 통하여 음원과 산란체까지의 도달시간과 전달손실을 계산 하였으며 경계면 산란 예측은 복합 거칠기(composite roughness) 모델을 이용하였다. 모델의 검증을 위하여 GSM(generic sonar model) 잔향음 모의 신호 및 실측 잔향음 신호와 비교하였으며 비교 결과 GSM 보다 HYREV 모델이 천해 잔향음 예측에 적합함을 확인할 수 있었다.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.6
• /
• pp.472-481
• /
• 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
• /
• v.21 no.8
• /
• pp.671-678
• /
• 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
• /
• v.28 no.8
• /
• pp.740-754
• /
• 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
• /
• v.21 no.8
• /
• pp.679-685
• /
• 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
• /
• v.38 no.1
• /
• pp.96-105
• /
• 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.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.429-432
• /
• 2002

천해에서의 저주파 단상태 잔향음 모델(L-HYREV)을 개발하였다. 음선이론에 기초한 전파모델은 해저 내로 투과되는 음파에 대한 효과를 적절하게 고려 할 수 없으므로, 해저 내 상호작용을 계산할 수 있는 전파모델이 필요하다. 따라서 본 논문에서는 RAM을 이용해서 전달손실을 계산 후, 다중경로 확장모델을 이용해서 산출한 전달손실을 보정하였다. 모델의 검증을 위하여 GSM(generic sonar model) 잔향음 모의 신호 및 실측잔향음 신호와 비교하였으며, 비교 결과 GSM 보다 L-HYREV 모델이 저주파 잔향음 예측에 적합함을 확인할 수 있다.

• The Journal of the Acoustical Society of Korea
• /
• v.13 no.6
• /
• pp.66-74
• /
• 1994

Simulation of sonar reverberation time series is very useful because most acoustic models are power level models and have a difficulty when performance of hardware system is evaluated under the reverberant condition. Thus, in this paper, the simulation of reverberation time series is attempted, First, normalized spectrum, whose bandwidth is varying in the frequency domain and which has zero-mean Gaussian distribution, is calculated at pre-selected receiving time. Second, reverberation levels given by underwater acoustic model are combined with normalized spectrum in the frequency domain. Finally, nonstationary sonar reverberation time series are simulated by IFT(Inverse Fourier Transform).

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.8
• /
• pp.389-394
• /
• 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
• /
• v.32 no.2
• /
• pp.104-115
• /
• 2013

In a shallow water waveguide, reverberation signals and their Doppler effects form the primary limitation on sonar system performance. Therefore, in the reverberation-limited environment, it is necessary to estimate the reverberation level to be encountered under the conditions in which the sonar system is operated. In this paper, high-frequency reverberation model capable of simulating the reverberation signals received by a high-speed moving source in a range independent waveguide is suggested. In this model, eigenray information from the source to each boundary is calculated using the ray-based approach and the optimizing method for the launch angles. And the source receiving position changed by the moving source is found by a scattering path-finding algorithm, which considers the speed and direction of source and sound speed to find the path of source movement. The scattering effects from sea surface and bottom boundaries are considered by APL-UW scattering models. The model suggested in this paper is verified by a comparison to the measurements made in August 2010. Lastly, this model reflects well statistical properties of the reverberation signals.