• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.235-239
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• 2004

Sound transmission either as airborne or structure borne is a potential problem that occurs in buildings either from sources within or from outside. With the expansion of real estate activities in countries like India, the need to attend sound insulation requirements also assumes greater dimensions. The focus of this research is on studying the sound transmission characteristics of building structures made of hollow blocks, neocrete block, aerocon block and prefabricated panels such as Ferrocement panel. The tests were carried out the blocks with and without plastering and their sound reduction index was measured at one-third octave frequencies. In the case of ferrocement panels, different types of systems were tested in the TL suite. Panels with cavity, with cavity ties, with insulation, with stiffeners and with plasterboard were investigated. Sound reduction index of these panels was measured with additional quantities like longitudinal wavespeed, and loss factors (internal and total loss factor). Tests were also conducted on Cypcrete wall panel and Sandwiched wooden panel in a similar way. Theoretical investigations were carried out using Statistical Energy Analysis (SEA) for the above systems. Sound reduction index was then compared between the predicted and the measured values.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.52-61
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• 2007

Temporal and spatial variations of sea water largely affect on the pattern of underwater sound propagation. Acoustic environmental changes and their effects on underwater sound propagation in the northern part of the East Sea, which have been poorly studied mainly due to lack of observations, are investigated by analyzing the hydrographic data acquired since 1993. Severe changes in acoustic environments are associated with various physical processes such as deep convection, thermal fronts, and eddies in the northern part of the East Sea. Spatio-temporal variations of sound speed field and the layer of the maximum sound speed are categorized into six typical cases. Using a sound source of 5 kHz, acoustic transmission losses are calculated range-independently for the six typical cases. Significant differences among the patterns of transmission loss in the six cases suggest that a different tactics are required when we operate in the northern part of the East Sea.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.276-279
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• 2008

In order to measure sound transmission loss (STL) of a shipboard window of small size, a special partition is built into the test opening between two reverberation rooms and the specimen is placed in that partition. For high sound insulation, the filler wall often has multi-layered structure such as double-brick wall or buckhead structure with thick steel plate, absorptive material, and sandwich panels. This paper discusses the installation method of a multi-layered filler wall that consist of gypsum boards, lead plates, and glass wool. The experimental results of various wall structures are introduced. The comparison between the results show that the sound bridge effect plays a significant role in lowering the maximum STL of the filler wall. It is also found that the higher the sound insulation performance of the filler wall is, the more important the franking transmission through other side wall of the test facility is.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1001-1004
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• 2002

Accurate prediction of the transmission loss of dissipative silencers has been considered difficult due to the ambiguity and complexity in the physical properties of sound absorbing materials. Additional difficulty lies in the fact that the analytical calculation of the propagation constant is unknown yet. In this paper. as a first step toward obtaining the Propagation constant and thus predicting the transmission loss, an approximation equation stemming from the wave analysis in the lined interior has been derived. Such an analytical solution and numerical solution using the boundary element method are compared for a two-dimensional simple dissipative silencer under the assumption of the locally reacting sound absorbent.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.1
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• pp.22-28
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• 2012

While a dash panel component, close to passengers, plays a very important role to protect heat and noise from a power train, it is also a main path that transfers vibration energy and eventually radiates acoustic noise into the cavity. Therefore, it is important to provide optimal design schemes incorporating sound packages such as a dash isolation pad and a floor carpet, as well as structures. The present study is the extension of the previous investigation how design variables affect sound radiation, which was carried out using the simple plate and framed system. A novel FE-SEA hybrid simulation model is used for this study. The system taken into account is a dash panel component of a sedan vehicle, which includes front pillars, front side members, a dash panel and corresponding sound packages. Design variables such as panel thicknesses and sound packages are investigated how they are related to two main NVH indexes, sound radiation power(i.e. structure-borne) and sound transmission loss(i.e. air borne). In the viewpoint of obtaining better NVH performance, it is shown that these two indexes do not always result in same tendencies of improvement, which suggests that they should be dealt with independently and are also dependent on frequency regions.

• International Journal of Railway
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• v.4 no.1
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• pp.19-27
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• 2011

Many studies for improving the railway vehicle's performance and comfort such as speed, weight and noise are currently in progress. Improving the structural characteristics of the vehicle for greater noise insulation is considered important for reducing disturbance due to noise, but measuring transmission loss entails large costs. This study explores an alternative method for estimating and measuring the railway vehicle's transmission loss that involves on applying the numerical analysis coupled with scaled reverberation chamber measurement. The transmission loss measurement using scaled reverberation chamber was performed after the compensation value was found through 1mm thickness(1t) specimen. For numerical analysis, a commercially available acoustics solver VA ONE was used. The proposed method is found to lead to transmission loss measurement comparable to the measurements based on large-scale reverberation chamber. Thus, it can be argued that a reliable method has been developed for measuring railway vehicle's transmission loss.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.1-10
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• 2016

To improve the sound insulation performance of laminated glass in high speed trains, it is beneficial to study the relationship between the characteristics of interlayer films and the acoustical performance. In addition to those of conventional PVB (polyvinyl butyral), the dynamic mechanical properties of PVB derivatives and PC (polycarbonate), which are candidates for interlayer films, were analyzed. We assumed that PVB-HEMU, which has a glass transition temperature ($T_g$) around room temperature and a large tan ${\delta}$ (loss tangent) value, can be made to damp efficiently. The damping capability was tested utilizing sound transmission loss measurement and simulation under the identical structure of laminated glass in high speed trains. We also built a database for analysis of relations between interlayer film characteristics and acoustical performance; this was followed by the determination of sound transmission loss using the intensity technique and FEA.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.1-6
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• 2008

Sound transmission characteristics are investigated on the test specimen for the railway vehicle's floor section. Transmission loss on the honeycomb structure has been examined experimentally with the reverberation chamber. Predicted transmission loss values using NASTRAN, AUTOSEA2, are compared with measured Haloes and the effect of resonance on the transmission loss is identified. Transmission loss of different shapes of honeycomb structure are predicted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.152-155
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• 2005

Diesel particulate filter (DPF) is comprised of a number of capillary tubes enclosed by porous ceramic wails, shaped like a plugged duct. Hot gas flows through the DPF along with the exhaust noise from Diesel engine. Based on previous works on the sound propagation through DPF, in this study, losses at entrance, exit, and ceramic walls are considered and the gradients in temperature and flow velocity are considered. Transfer matrix at entrance, monolith, and exit parts are obtained by employing the segmental approach in analyzing the sound propagation through DPF. The predicted transmission loss agrees very well with the empirical one, which is measured by the improved method with correction terms.

• Korean Journal of Audiology
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• v.24 no.4
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• pp.174-179
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• 2020

Background and Objectives: The integration of auditory-visual speech information improves speech perception; however, if the auditory system input is disrupted due to hearing loss, auditory and visual inputs cannot be fully integrated. Additionally, temporal coincidence of auditory and visual input is a significantly important factor in integrating the input of these two senses. Time delayed acoustic pathway caused by the signal passing through digital signal processing. Therefore, this study aimed to investigate the effects of hearing loss and hearing aid digital delay circuit on sound-induced flash illusion. Subjects and Methods: A total of 13 adults with normal hearing, 13 with mild to moderate hearing loss, and 13 with moderate to severe hearing loss were enrolled in this study. Subsequently, the sound-induced flash illusion test was conducted, and the results were analyzed. Results: The results showed that hearing aid digital delay and hearing loss had no detrimental effect on sound-induced flash illusion. Conclusions: Transmission velocity and neural transduction rate of the auditory inputs decreased in patients with hearing loss. Hence, the integrating auditory and visual sensory cannot be combined completely. Although the transmission rate of the auditory sense input was approximately normal when the hearing aid was prescribed. Thus, it can be concluded that the processing delay in the hearing aid circuit is insufficient to disrupt the integration of auditory and visual information.