acoustic performance
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2022 ◽  
Vol 294 ◽  
pp. 118616
Author(s):  
Ji Yong Choi ◽  
Beom Yeol Yun ◽  
Young Uk Kim ◽  
Yujin Kang ◽  
Sung Chan Lee ◽  
...  

2022 ◽  
pp. 1-18
Author(s):  
Gyani Shankar Sharma ◽  
Masahiro Toyoda ◽  
Alex Skvortsov ◽  
Ian MacGillivray ◽  
Nicole Kessissoglou

Abstract Time and frequency domain numerical models are developed to investigate the acoustic performance of metasurface coatings for marine applications. The coating designs are composed of periodic air-filled cavities embedded in a soft elastic medium, which is attached to a hard backing and submerged in water. Numerical results for a metamaterial coating with cylindrical cavities are favourably compared with analytical and experimental results from the literature. Frequencies associated with peak sound absorption as a function of the geometric parameters of the cavities and material properties of the host medium are predicted. Variation in the cavity dimensions that modifies the cylindrical-shaped cavities to flat disks or thin needles is modelled. Results reveal that high sound absorption occurs when either the diameter or length of the cavities is reduced. Physical mechanisms governing sound absorption for the various cavity designs are described.


Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 118
Author(s):  
Jiamin Chen ◽  
Chenyang Xue ◽  
Yongqiu Zheng ◽  
Jiandong Bai ◽  
Xinyu Zhao ◽  
...  

The ideal development direction of the fiber-optic acoustic sensor (FOAS) is toward broadband, a high sensitivity and a large dynamic range. In order to further promote the acoustic detection potential of the Fabry–Pérot etalon (FPE)-based FOAS, it is of great significance to study the acoustic performance of the FOAS with the quality (Q) factor of FPE as the research objective. This is because the Q factor represents the storage capability and loss characteristic of the FPE. The three FOASs with different Q factors all achieve a broadband response from 20 Hz to 70 kHz with a flatness of ±2 dB, which is consistent with the theory that the frequency response of the FOAS is not affected by the Q factor. Moreover, the sensitivity of the FOAS is proportional to the Q factor. When the Q factor is 1.04×106, the sensitivity of the FOAS is as high as 526.8 mV/Pa. Meanwhile, the minimum detectable sound pressure of 347.33 μPa/Hz1/2  is achieved. Furthermore, with a Q factor of 0.27×106, the maximum detectable sound pressure and dynamic range are 152.32 dB and 107.2 dB, respectively, which is greatly improved compared with two other FOASs. Separately, the FOASs with different Q factors exhibit an excellent acoustic performance in weak sound detection and high sound pressure detection. Therefore, different acoustic detection requirements can be met by selecting the appropriate Q factor, which further broadens the application range and detection potential of FOASs.


Author(s):  
Mohamed Said Abbas ◽  
Antonin Fabbri ◽  
Mohammed Yacine Ferroukhi ◽  
Philippe Glé ◽  
Emmanuel Gourdon ◽  
...  

Bio-based materials are an environmentally friendly alternative to classic construction materials, yet their generally low density can lead to poor acoustic properties. The acoustic performance of hemp shiv and sunflower pith composites is therefore analyzed using Kundt’s tube. Although the loose aggregates present an exceptional sound absorbing behavior, it can be notably worsened in the presence of certain binders. The Transmission Loss is nevertheless enhanced by the binders, although it does not exceed 20 dB in most cases. For both properties, the type of binder has been found to be the most influential parameter. Through the Kundt’s tube method, it is also possible to determine the geometrical parameters of the composites’ microstructure, which have been observed to be similar for materials presenting comparable hygrothermal properties and containing the same binder. In a previous work, an experimental correlation was found between the thermal conductivity and the interparticle porosity of the aforementioned composites, which is compared to theoretical thermal conductivity models from literature without finding any apparent correspondence.


Author(s):  
Said Bouzit ◽  
Francesca Merli ◽  
Mohammed Sonebi ◽  
Sofiane Amziane ◽  
Cinzia Buratti ◽  
...  

The building sector is one of the biggest consumers of energy in the world and it is pushing the scientific community to find various alternative solutions to solve the problem of thermal insulation of buildings. Therefore, the selection of appropriate building materials is a major challenge for improving the thermal comfort and energy performance of buildings. In this scenario, the interest of plaster-based composites as insulating materials increases, in particular for new applications, as insulators for the building envelope, and this deserves to be studied. In this investigation, new plaster-based composites with cork were produced and tested at lab scale, in order to obtain cheap solutions with improved thermo-physical and acoustic performance. The results show that it is possible to improve the thermal, mechanical, and acoustic performance of construction biomaterials by using plaster as a binder and cork as a natural reinforcement: thermal conductivity was equal to 0.097 W/m.K, the compressive strength to about 2.30 MPa, and the transmission loss to about 40 dB. Keywords: Plaster-Gypsum; Cork; Thermal, Mechanical and Acoustic Properties.


Author(s):  
Abhishek Kumar Tewari ◽  
R Vijayakumar

Underwater Radiated Noise (URN) emanating from surface and underwater marine platforms has become a significant concern for all the Nations in view of the global requirement to minimise the increasing adverse impact on marine mammals and fishes and maintain ecological balance in the ‘Silent’ ocean environment. Ambient noise level in the sea, in 10 to 300 Hz frequency band, has increased by 20 to 30 dB due to shipping (Wittekind, 2009). Marine propeller (in non- cavitating and cavitating regime) is a potential contributor to the ships noise and a lot of scientific research has been undertaken and considerable progress has been achieved in estimating the hydro-acoustic performance of marine propellers. In light of this, the scope of this paper is to review and critically examine the various methods used for estimating the hydro-acoustic performance of marine propellers, particularly in the non-cavitating regime, over the past many years. This review paper brings out the details, applicability, merits and demerits of various methods, extrapolation laws to obtain full scale results, scientific conclusion of all the know-how on this subject and the scope of further research as perceived by the authors. This paper also presents a numerical methodology to estimate the noise radiated by a DTMB 4119 model propeller in the non-cavitating regime in open water condition. The hydrodynamic analysis of the propeller was performed using commercial CFD software STARCCM+, closure was achieved using standard k-ε turbulence model and hydro-acoustic predictions have been performed using FWH acoustic analogy. The results compare very well with the published literature.


2021 ◽  
Vol 241 ◽  
pp. 110078
Author(s):  
Tianzhu Gao ◽  
Yang Lin ◽  
Liang Qiu ◽  
Zion Tsz Ho Tse ◽  
Hongliang Ren

2021 ◽  
Vol 44 ◽  
pp. 103362
Author(s):  
Sen Lin ◽  
Genbao Zhang ◽  
Junbo Sun ◽  
Shilin He ◽  
Changfu Chen ◽  
...  

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