Acoustic characterization of a nonlinear vibroacoustic absorber at low frequencies and high sound levels

In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium could be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.

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Acoustic Characterization of Marine Sediments

10.21236/ada627576 ◽

1997 ◽

Author(s):

Anatoliy N. Ivakin ◽

Darrell R. Jackson

Keyword(s):

Marine Sediments ◽

Acoustic Characterization

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In Vitro Characterization of the Antibacterial Spectrum of Novel Bacterial Type II Topoisomerase Inhibitors of the Aminobenzimidazole Class

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.50.4.1228-1237.2006 ◽

2006 ◽

Vol 50 (4) ◽

pp. 1228-1237 ◽

Cited By ~ 56

Author(s):

Nagraj Mani ◽

Christian H. Gross ◽

Jonathan D. Parsons ◽

Brian Hanzelka ◽

Ute Müh ◽

...

Keyword(s):

Bacterial Resistance ◽

Wide Spectrum ◽

Dna Gyrase ◽

Antibacterial Activities ◽

Mechanisms Of Action ◽

Fluoroquinolone Resistance ◽

Topoisomerase Iv ◽

Low Frequencies

ABSTRACT Antibiotics with novel mechanisms of action are becoming increasingly important in the battle against bacterial resistance to all currently used classes of antibiotics. Bacterial DNA gyrase and topoisomerase IV (topoIV) are the familiar targets of fluoroquinolone and coumarin antibiotics. Here we present the characterization of two members of a new class of synthetic bacterial topoII ATPase inhibitors: VRT-125853 and VRT-752586. These aminobenzimidazole compounds were potent inhibitors of both DNA gyrase and topoIV and had excellent antibacterial activities against a wide spectrum of problematic pathogens responsible for both nosocomial and community-acquired infections, including staphylococci, streptococci, enterococci, and mycobacteria. Consistent with the novelty of their structures and mechanisms of action, antibacterial potency was unaffected by commonly encountered resistance phenotypes, including fluoroquinolone resistance. In time-kill assays, VRT-125853 and VRT-752586 were bactericidal against Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis, and Haemophilus influenzae, causing 3-log reductions in viable cells within 24 h. Finally, similar to the fluoroquinolones, relatively low frequencies of spontaneous resistance to VRT-125853 and VRT-752586 were found, a property consistent with their in vitro dual-targeting activities.

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Descriptive characterization of sound levels in an environmental justice city before and during a global pandemic

Environmental Research ◽

10.1016/j.envres.2021.111353 ◽

2021 ◽

pp. 111353

Author(s):

Erica D. Walker ◽

Nina F. Lee ◽

Madeleine K. Scammell ◽

Arielle P. Feuer ◽

Maria B. Power ◽

...

Keyword(s):

Environmental Justice ◽

Global Pandemic ◽

Sound Levels

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Low temperature acoustic characterization of PMN single crystal

Journal of Applied Physics ◽

10.1063/1.5000361 ◽

2017 ◽

Vol 122 (8) ◽

pp. 084103 ◽

Cited By ~ 1

Author(s):

E. Smirnova ◽

A. Sotnikov ◽

S. Ktitorov ◽

H. Schmidt

Keyword(s):

Low Temperature ◽

Single Crystal ◽

Acoustic Characterization

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Acoustic characterization of silica nanoparticle-impregnated Kevlar fabric

Textile Research Journal ◽

10.1177/00405175211023812 ◽

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.

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Acoustic Characterization of Some Steel Industry Waste Materials

Applied Sciences ◽

10.3390/app11135924 ◽

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.

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