Passive time-reversal mirror for acoustic characterization of the seabed

2021 ◽  
Vol 150 (4) ◽  
pp. A193-A194
Author(s):  
Oleg A. Godin ◽  
Dexter Tan ◽  
Tsu Wei Tan
Keyword(s):  
Time Reversal ◽  
Acoustic Characterization ◽  
Time Reversal Mirror

Real‐time characterization of unstationary flows using a time‐reversal mirror

1998 ◽  
Vol 103 (5) ◽  
pp. 2910-2910
Author(s):  
Agnes Maurel ◽  
Julien De Rosny ◽  
Sebastien Manneville ◽  
Philippe Roux ◽  
Mathias Fink
Keyword(s):  
Real Time ◽  
Time Reversal ◽  
Time Reversal Mirror

Acoustic Characterization of Marine Sediments

1997 ◽  
Author(s):  
Anatoliy N. Ivakin ◽  
Darrell R. Jackson
Keyword(s):  
Marine Sediments ◽  
Acoustic Characterization

Low temperature acoustic characterization of PMN single crystal

2017 ◽  
Vol 122 (8) ◽  
pp. 084103 ◽  
Author(s):  
E. Smirnova ◽  
A. Sotnikov ◽  
S. Ktitorov ◽  
H. Schmidt
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Acoustic Characterization

scholarly journals M-ary nonlinear sine chirp spread spectrum for underwater acoustic communication based on virtual time-reversal mirror method

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Songzuo Liu ◽  
Habib Hussain Zuberi ◽  
Yi Lou ◽  
Muhmmad Bilal Farooq ◽  
Shahabuddin Shaikh ◽  
...  
Keyword(s):  
Acoustic Communication ◽  
Time Reversal ◽  
Spread Spectrum ◽  
Underwater Acoustic Communication ◽  
Half Cycle ◽  
Spreading Factor ◽  
Underwater Acoustic ◽  
Virtual Time ◽  
Chirp Spread Spectrum ◽  
Time Reversal Mirror

AbstractLinear chirp spread spectrum technique is widely used in underwater acoustic communication because of their resilience to high multipath and Doppler shift. Linear frequency modulated signal requires a high spreading factor to nearly reach orthogonality between two pairs of signals. On the other hand, nonlinear chirp spread spectrum signals can provide orthogonality at a low spreading factor. As a result, it improves spectral efficiency and is more insensitive to Doppler spread than the linear counterpart. To achieve a higher data rate, we propose two variants (half cycle sine and full cycle sine) of the M-ary nonlinear sine chirp spread spectrum technique based on virtual time-reversal mirror (VTRM). The proposed scheme uses different frequency bands to transmit chirp, and VTRM is used to improve the bit error rate due to high multipath. Its superior Doppler sensitivity makes it suitable for underwater acoustic communication. Furthermore, the proposed method uses a simple, low-power bank of matched filters; thus, it reduces the overall system complexity. Simulations are performed in different underwater acoustic channels to verify the robustness of the proposed scheme.

Acoustic characterization of silica nanoparticle-impregnated Kevlar fabric

2021 ◽  
pp. 004051752110238
Author(s):  
Oluwafemi P Akinmolayan ◽  
James M Manimala
Keyword(s):  
Transmission Loss ◽  
Silica Nanoparticle ◽  
Air Gap ◽  
Thin Plates ◽  
Residual Porosity ◽  
Ballistic Performance ◽  
Number Of Layers ◽  
Structural Applications ◽  
Acoustic Characterization

Silica nanoparticle-impregnated Kevlar (SNK) fabric has better specific ballistic performance in comparison to its neat counterparts. For multifunctional structural applications using lightweight composites, combining this improved ballistic functionality with an acoustic functionality is desirable. In this study, acoustic characterization of neat and SNK samples is conducted using the normal-incidence impedance tube method. Both the absorption coefficient and transmission loss (TL) are measured in the 60–6000 Hz frequency range. The influence of parameters such as number of layers of neat or treated fabric, percentage by weight of nanoparticle addition, spacing between fabric layers, and residual porosity is examined. It is found that while absorption decreases with an increase in nanoparticle addition for frequencies above about 2500 Hz, increasing the number of layers shifts peak absorption to lower frequencies. By introducing an air-gap behind the fabric layer, dominant low-frequency (1000–3000 Hz) absorption peaks are obtained that correlate well with natural modes of mass-equivalent thin plates. Examining the influence of residual porosity by laminating the SNK samples reveals that it contributes to about 30–50% of the total absorption. Above about 1500 Hz, 3–5 dB of TL increase is obtained for SNK samples vis-à-vis the neat samples. TL is found to increase beyond that of the neat sample above a threshold frequency when an air-gap is introduced between two SNK layers. With an increase in the weight of nanoparticle addition, measured TL tends to be closer to mass law predictions. This study demonstrates that SNK fabric could provide improved acoustic performance in addition to its ballistic capabilities, making it suitable for multifunctional applications and could form the basis for the development of simplified models to predict the structural acoustic response of such nanoparticle–fabric composites.

scholarly journals Acoustic Characterization of Some Steel Industry Waste Materials

2021 ◽  
Vol 11 (13) ◽  
pp. 5924
Author(s):  
Elisa Levi ◽  
Simona Sgarbi ◽  
Edoardo Alessio Piana
Keyword(s):  
Thermal Characteristic ◽  
Environmental Benefits ◽  
Acoustic Properties ◽  
Physical Parameters ◽  
Industry Waste ◽  
Acoustic Characterization ◽  
Minimization Procedure ◽  
The Difference ◽  
By Products

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.

Acoustic characterization of laser-induced graphene film thermoacoustic loudspeakers

2019 ◽  
Author(s):  
Paolo La Torraca ◽  
Luca Larcher ◽  
Paolo Lugli ◽  
Marco Bobinger ◽  
Francisco J. Romero ◽  
...  
Keyword(s):  
Graphene Film ◽  
Acoustic Characterization

Demonstration of a high-frequency acoustic barrier with a time-reversal mirror

2003 ◽  
Vol 28 (2) ◽  
pp. 246-249 ◽  
Author(s):  
H. Song ◽  
W.A. Kuperman ◽  
W.S. Hodgkiss ◽  
T. Akal ◽  
P. Guerrini
Keyword(s):  
Time Reversal ◽  
High Frequency ◽  
Time Reversal Mirror
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