Papers by Keyword: Acoustic Properties

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Authors: Anis Nazihah Mat Daud, Md Supar Rohani, Rosly Jaafar
Abstract: Acoustic properties are the main criteria to evaluate the compatibility of tested materials as a medical phantom. We determined the acoustic properties of konjac glucomannan (KGM) gel to verify its compatibility as a medical phantom. The acoustic properties measurement employed ultrasonic insertion technique and utilized two identical transducers of 5 MHz center frequencies. One KGM gel block with 5.62 mm thickness was used as sample to determine its longitudinal speed, acoustic impedance and attenuation coefficient at three different water temperatures; (21.5 ± 0.1), (22.5 ± 0.1) and (23.5 ± 0.1) °C. Findings indicated that its longitudinal speed and acoustic impedance increased from (1495 ± 1) to (1499 ± 1) m s-1 and (1.555 ± 0.001) to (1.559 ± 0.001) × 106 kg m-2 s-1 as the water temperature increased from (21.5 ± 0.1) to (23.5 ± 0.1) °C. It also indicated that its attenuation coefficient varied around (0.1303 ± 0.0107) to (0.1373 ± 0.0103) dB cm-1 with increasing water temperature. KGM gel is compatible to be a medical phantom since its acoustic properties are comparable to the acoustic properties of human soft tissue.
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Authors: Yan Liu, Xiao Juan Zhang, Zong Cai Liu
Abstract: With the development of the car industry, the pace of the urban construction is accelerating as well. Cars have gradually entered the ordinary family. As the car noise has a big effect on the health of the passengers, as well as on the surroundings, one of the car industry key duties is the car noise reduction. By researching the materials applied to car, this article describe that PU material could reduce the impact of the engine noise on the cab efficiently; Polypropylene needle-spun felt could reduce the noise passed by chassis; PET material's sound absorption is poor in mid bass, however in high frequency it's sound absorption is good; sound absorbing sponge can reduce the low and high frequency noise; The combine sponge can reduce the noise from the tire and transmission system ; Cotton material could absorb the high frequency noise.
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Authors: Samson Rwawiire, Blanka Tomkova, Jiří Militký, Lubos Hes, Bandu Madhukar Kale, Abdul Jabbar
Abstract: The desire to mitigate climate change due to greenhouse gas emissions has led to the exploration of plant fibers as alternative materials for various industrial applications acoustics inclusive. In this investigation, sound absorption properties of barkcloth, a nonwoven fabric from Antiaris toxicaria were characterized. Theoretical empirical sound absorption models based on Delany and Bazley such as Miki, Wu and Allard – Champoux were utilized to validate the experimental data. The empirical models were in agreement with experimental data; Incorporation of an air-gap between the fabric layers had a positive influence on the overall sound absorption behavior of barkcloth fabrics rendering the fabric a good sound absorption material.
201
Authors: Ling Dong Li, Yuan Fang Cheng, Xiao Jie Sun
Abstract: As a kind of emerging energy with massive reserves, natural gas hydrates are becoming the hot spot of global research. The elastic properties of gas hydrate bearing sediments (HBS) are the fundamental parameters for gas hydrates exploration and resource evaluations. As the original coring in HBS is difficult and expensive, experimental method is important to study the problem. An acoustic wave in-situ measuring system for HBS was developed. Using the in-situ method, hydrate bearing rock samples of different hydrate saturation were synthesized, of which the supersonic wave measurement was carried out under different confining pressure. According to the elasticity theory, the dynamic elastic parameters were obtained using the measured ultrasonic wave velocity. The results show that compressional and shear waves increase with the confining pressure and hydrate saturation increasing, and so the dynamic elastic modulus is.
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Authors: Yuriy Suhak, Michal Schulz, Denny Richter, Holger Fritze
Abstract: Acoustic characteristics and electrical conductivity of CTGS, LGT and LGS bulk acoustic wave resonators operated at the fundamental mode in the temperature range of 20-1470°C are studied. It is shown that LGS and CTGS resonators can be excited piezoelectrically up to 1470 and 1270°C, respectively, which is close to their melting temperatures. The electrical conductivity of CTGS is found to be by at least two and three orders of magnitude lower than that of LGS and LGT, respectively, over the temperature range 400-1000°C. Measurements of temperature dependent electromechanical losses show, that they are at least by two orders of magnitude lower in CTGS comparing to that in LGS within the measured temperature range.
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Authors: Iveta Skotnicova, Nada Zdrazilova, Roman Fojtik, Pavel Oravec
Abstract: The article deals with dynamic and acoustic characteristics of the temporary steel bridge structures. Their construction is usually associated with the need of temporary replacement of the permanent bridge structures which were damaged or completely destroyed due to natural disasters or by human forces during the military operations or terrorist attacks. If some area is affected such this disaster, it usually gets into the difficult economic situation and it is not possible to recover the permanent construction in real time. In many cases there arises a situation that the temporary structure performs its function for years or permanently. In view of this fact, it is necessary to solve a number of defects, especially with regard to the long-term dynamic stresses in the structure and to excessive noise, which arises due to the traffic, because this structure is not primarily designed for it.
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Authors: Grzegorz Kmita, Michal Kozupa, Robert Platek, Julita Krol, Grzegorz Juszkiewicz
Abstract: Design considerations related to noise pollution have become extremely important recently in many industries. Despite the wide range of applications and various noise spectrum the methodology remains quite common. The power products operating in the power systems are very often affected by a noise emission side effect and must be carefully designed with respect to the resulting noise emission and its influence on the surrounding environment consequently. Noise management, design concept examples as well as the modern techniques for noise sources characterization in transformers are presented in this paper.
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