scholarly journals Bayesian reconstruction of the inflaton’s speed of sound using CMB data

2021 ◽  
Vol 103 (12) ◽  
Author(s):  
Guadalupe Cañas-Herrera ◽  
Jesús Torrado ◽  
Ana Achúcarro
Keyword(s):  
Speed Of Sound ◽  
Bayesian Reconstruction

Response to “Oil-Based Gel Phantoms and the Speed of Sound”

2020 ◽  
Vol 46 (11) ◽  
pp. 3172
Author(s):  
Natasha Alves ◽  
Brian K. Courtney
Keyword(s):  
Speed Of Sound

AN IMPROVED ARMORED VEHICLE KRAZ “FIONA” NOISE SILENCER

2019 ◽  
pp. 21-26
Author(s):  
Volodymyr Fedorov ◽  
Vasyl’ Yanovsky ◽  
Dmytro Kovalshuk
Keyword(s):  
Noise Reduction ◽  
Speed Of Sound ◽  
Acoustic Waves ◽  
Noise Level ◽  
Combustion Engine ◽  
Environmental Aspect ◽  
Exhaust Gases ◽  
Ecological Requirements ◽  
On The Road ◽  
Armored Vehicle

Ecological requirements for cars grow from year to year, both in the world as a whole, and in Ukraine in particular. This is especially true of noise pollution. Additionally, noise reduction becomes relevant, taking into account the conduct of military operations during the last 5 years on the territory of Ukraine. The war has caused a special need for military vehicles for which masking properties are vital. Noise is a serious disincentive factor. Therefore, its reduction for a military vehicle, apart from the environmental aspect, is of a purely military nature, that is, it is extremely important. The car has many sources of noise there are many ways to deal with them. One of the most powerful source of noise is the sleeping bag. This kind of noise is reduced by means of silencers of noise. The vast majority of silencer data in the basis of its design has a reactive (or resonant) muffler. To calculate the jet silencer you must know the speed of sound in the sleeping bags. In order to increase the acoustic efficiency of reactive and resonant mufflers of exhaust gases noise of the ICE of cars, an experimental method was proposed for determining the speed of sound in the sleighs. Implementation of the method is carried out by measuring the attenuation of acoustic waves. The noise level of the bedrooms is measured without silencer and silencer. Based on the data obtained, the noise reduction performance of the residual is established. From the well-known formula, based on the calculation of the efficiency of the silencing of a jet muffler, a formula is obtained for calculating the speed of sound in the sleeping quays. In this formula, all parameters are known: the level of silencer efficiency, the noise level of the sleeping, the ratio of areas of cross sections of the muffler and the inlet pipe and the length of the muffler. The sound speed thus established can continue to be used not only for engines of the type for which measurements and calculations were made, but also with a certain approximation for some other types of engines. This method provides high accuracy for determining the required parameter. In the given work on the example of the armored car KrAZ “Fiona” the calculation of efficiency increase of the reactive silencer is made due to the above-mentioned method. Also, the projected decrease in the external noise level of the KrAZ Armored Vehicle “Fiona” is considered by determining the speed of sound in the recesses on the trunk cycle on the road with acceleration up to speed of 50 km/h (75 km/h) and the movement with this speed, as well as when driving at a speed of 45 km/h. Keywords: transport, armored car, internal combustion engine, exhaust, exhaust gases, noise, source, acoustic efficiency, acoustic efficiency, speed of sound, jet muffler.

The study of acoustic scattering from a single sound-permeable sphere

2018 ◽  
Vol 13 (4) ◽  
pp. 79-91 ◽  
Author(s):  
E.Sh. Nasibullaeva
Keyword(s):  
Speed Of Sound ◽  
Numerical Technique ◽  
Acoustic Scattering ◽  
Computer Time ◽  
Physical Parameters ◽  
Fast Method ◽  
Scattering Field ◽  
Permeable Sphere ◽  
Test Verification ◽  
Good Agreement

The paper presents a generalized mathematical model and numerical investigation of the problem of acoustic scattering from a single sound-permeable sphere during the passage of two types of waves - spherical from a monopole radiation source and a plane one. In solving the Helmholtz equation, a numerical technique based on the fast method of multipoles is used, which allows achieving high accuracy of the results obtained at the lowest cost of computer time. The calculations are compared with known experimental data and a good agreement is obtained. The formulas for calculating the main characteristic of the scattering field (the total scattering cross section) for a sound-permeable sphere are generalized. The effect on this characteristic of the physical parameters of media outside and inside the sphere, such as the density and speed of sound, is shown. A numerical parametric analysis of the pressure distribution around a single sound-permeable sphere for different values of the wave radius, density, and speed of sound of the outer and inner medium of the sphere is carried out. The obtained results will later be used for test verification calculations for the numerical solution of the generalized problem of acoustic scattering of a set of sound-permeable spheres (coaxial or arbitrarily located in space).

Ground Transportation: Ships

2017 ◽  
Author(s):  
Peter Rez
Keyword(s):  
Speed Of Sound ◽  
Projected Area ◽  
Drag Coefficients ◽  
Wetted Area ◽  
Large Container ◽  
Density Of Water

The drag on ships comes from movement through the water. There is a part that is analogous to the parasitic drag in aircraft, and a part that comes from creating the bow and stern waves—in some ways similar to the compressibility drag in aircraft that approach the speed of sound. Given that the density of water is more than 800 times that of air, speeds through the water are slower. Drag coefficients are specified differently for ships than for cars, trucks and airplanes. The relevant area is the total wetted area, and not the frontal projected area. Ships can be very efficient—the very powerful two-stroke diesels that power large container ships and tankers can be over 50% thermally efficient.

Speed-of-Sound Measurements and a Fundamental Equation of State for Propylene Glycol

2021 ◽  
Vol 50 (2) ◽  
pp. 023105
Author(s):  
Tim Eisenbach ◽  
Christian Scholz ◽  
Roland Span ◽  
Diego Cristancho ◽  
Eric W. Lemmon ◽  
...  
Keyword(s):  
Equation Of State ◽  
Propylene Glycol ◽  
Speed Of Sound ◽  
Fundamental Equation ◽  
Fundamental Equation Of State
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