PDF superior ANALYSIS OF A SOUND SPEED MEASUREMENT MADE IN 1738

ANALYSIS OF A SOUND SPEED MEASUREMENT MADE IN 1738

ANALYSIS OF A SOUND SPEED MEASUREMENT MADE IN 1738

“It came the time of the observation, that was made very carefully, and although two different flare-ups were seen, we did not perceive any shot. As the running wind was very soft, we attribute this defect to the many peaks and deeps which there were between the positions in that place, where the sound, without any doubt, was lost reflecting in the Quebradas with more than 100 toesas depth, and the high Montes, because the Pambamarca, where we were, had 883,5 toesas of height, counted from the flat ground where it raises. (Juan 1848, pp. 136-137)
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5 Lee mas

High pressure density and speed of sound of hydrofluoroether fluid 1,1,1,2,2,3,4,5,5,5 decafluoro 3 methoxy 4 (trifluoromethyl) pentane (HFE 7300)

High pressure density and speed of sound of hydrofluoroether fluid 1,1,1,2,2,3,4,5,5,5 decafluoro 3 methoxy 4 (trifluoromethyl) pentane (HFE 7300)

The speed of sound, c, in pure HFE-7300 was measured by using an Anton Paar DSA 5000 vibrating tube densitometer and sound analyzer automatically thermostatted within ±0.01 K. This device uses a propagation time technique [13 - 15] to determine the speed of sound of the sample. The apparatus has two transducers in which one acts as an emitter, and the other as receiver, working in a frequency of approximately 3 MHz. The measurements were performed at 0.1 MPa and at temperatures: 293.15, 298.15, 303.15, 313.15, 323.15 and 333.15 K. The calibration of this apparatus, performed once a week and every time a new temperature was set, was made with ambient air and Millipore quality water following the manufacturer’s instructions. The results of the calibrations were compared with those of references [11] for water, and [16] for air. Prior to make any measurement, the samples were degassed for at least 15 minutes in an ultrasonic bath PSelecta model Ultrasons H. The standard uncertainty for the ambient pressure (0.1 MPa), measured by using a Lambrecht model 604 barometer, is determined to be U(P 0.1 )= 10 -4 MPa. The accuracy for the speed of sound measurements is 0.5
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23 Lee mas

Change of pulses propagating in SOFAR Channel by moving front

Change of pulses propagating in SOFAR Channel by moving front

The ocean acoustic tomography measures propagation time of sound wave pulses and, from its data, evaluates the sound speed field and temperature field. Therefore this measurement requires exact knowledge on the sound wave propagation and identification of pulses. We verified the changes of sound waves passing through the transfer area, in which the sound wave profile changes significantly in the middle of propagation path, by using the wave theory. Results showed that the change in time of received pulse associated with the movement of a transfer area is periodical. Therefore the change in propagation time of the eigenray against transmission angle can be expressed as a circle trace with the distance of area 1 as a parameter. Analysis by the wave theory reveals effects of reflections on boundaries in the transfer area.
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6 Lee mas

Miniaturized optical sensors based on lens arrays

Miniaturized optical sensors based on lens arrays

The important question that has to be solved is, how dynamic speckles from dynamic structures are changed by an intermediate optical system? To employ the measurement scheme to be presented in the next part, we need to convert the dynamic speckles arising from e.g. a rotating object into a linear displacement in front of the basic optical system. Furthermore, we need to do it in a way such that the conversion between the dynamical properties of the object is simple. Finally, we need to establish a concept in which the result depends as little as possible on other parameters, i.e. the measurement scheme is “clean” and not susceptible to interference from secondary parameters. In the case of measuring rotation, we will pursue setups that are not influenced by any translation of the
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5 Lee mas

Pantograph noise measurements in Madrid-Sevilla high speed train (AVE)

Pantograph noise measurements in Madrid-Sevilla high speed train (AVE)

Afterwards, the sound power level value has been used as an input for a SEA model which also included vibro-acoustical characterization of the train elements [4]. Figure 8 shows the results of SEA modeling, it reveals that in the passengers zone under the pantograph this become the main source although it is not of the same importance along the rest of the train. As a consequence of the fact that the pantograph becomes the main source on its influence area, it was agreed with the train builder to reinforce the acoustical insulation of the roof with additional barrier/absorbent layers in the surroundings of the pantograph zone, in order to keep the estimated noise levels within specifications in this specific zone.
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8 Lee mas

USING THE STRUCTURAL REVERBERATION TIME IN STANDARDIZING LABORATORY MEASUREMENTS OF THE SOUND REDUCTION INDEX

USING THE STRUCTURAL REVERBERATION TIME IN STANDARDIZING LABORATORY MEASUREMENTS OF THE SOUND REDUCTION INDEX

The required loss factor for laboratory facilities has not received much attention, maybe due to the fact that it is not easy to adjust a laboratory to a desired loss factor. However, the importance has now clearly been demonstrated by a German Round Robin [6]. In that context also the measurement method for the loss factor has been studied and well established [7]. Furthermore, the established prediction method actually requires the use of the total loss factor (structural reverberation time) in the laboratory and the field situation [8]. This would be simplified if the structural reverberation time in the laboratory situation would be measured and presented for all heavier elements. To simplify that presentation, it has been proposed to convert all measurement results to a reference structural reverberation time, being representative for a typical field situation [9]. The advantages would be that - at least for simplified prediction models - the converted sound reduction index could be used without any adjustment to the actual structural reverberation time. The obvious disadvantage is of course that a 'typical field situation' does not exist. The values proposed in [9] deviate for instance substantially from those mentioned by Craik [10] as 'typical field values'. Furthermore, converting the measurement results to a reference situation is not as straight forward as it seems. Some more problems need to be solved
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6 Lee mas

SOUND MEASUREMENT BY LASER DOPPLER ANEMOMETRY

SOUND MEASUREMENT BY LASER DOPPLER ANEMOMETRY

Small particles suspended in the fluid scatter some of this light. The number of photons scattered depends on a variety of factors, such as the number and size of the particles, the intensity of the laser beam and their position within the interference pattern, and this number changes as the particles follow the fluid motion. A photomultiplier records some of this scattered light; if its intensity is sufficiently small, corresponding to an average of less than 40 million photons per second (one per 25ns), individual photons can be counted. The temporal photon distribution can then be auto-correlated, and the form of the auto-correlation function (ACF) used to determine features of the flow, such as its velocity.
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6 Lee mas

Assigning Numerical Scores to Linguistic Expressions

Assigning Numerical Scores to Linguistic Expressions

Taking into account the last ideas in Example 3, in which an extended order was defined on L but not necessarily on the whole power set of L, we may realize that, at this stage, an interesting question appears. Suppose that we are given a set of criteria for extension of a linear order from a set U to its power set. Assume also that, as it is the case of Kannai–Peleg’s theorem ([16]), such set of criteria provokes an impossibility result. Even if this happens, when we try to extend the ordering < defined on the set L = { l 1 , l 2 , . . . , l g } of labels, to its corresponding set L of linguistic expressions, it may still happen that an extension that accomplishes the criteria is possible. The reason is that L is much smaller than the whole power set of L. Sometimes, due to this restriction of domain, the extension could still be obtained. Similar questions, namely impossibility theorems in which the intrinsic impossibility actually disappears when a suitable restriction of domain is done, have been analyzed in depth in the contexts of Social Choice (see e.g., Gaertner [22]).
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17 Lee mas

A MULTIFREQUENCY SCINTILLATION SENSING OF RANGE DEPENDENT CURRENT

A MULTIFREQUENCY SCINTILLATION SENSING OF RANGE DEPENDENT CURRENT

here, k n = ω n / c is the wave number, c is the sound velocity, and µ ( x , y , z , t ) are the refraction index fluctuations. The sound waves are thought propagate along the x -axis, which is a horizontal line connected to a point sound source ( x = 0 ) and a non-directional receiver ( x = L ), the axis z directs vertically. The relative coherence of the signals can be characterized by the cross correlation function and its Fourier transform, i.e., the cross spectrum. The cross spectrum of the log-amplitude temporal fluctuations is

6 Lee mas

Aeroacoustic noise prediction in high speed trains due to attached and detached flow

Aeroacoustic noise prediction in high speed trains due to attached and detached flow

Abstract. This paper aims to set out the influence of the flow field around high speed trains in open field. To achieve this parametric analysis of the sound pressure inside the train was performed. Three vibroacoustic models of a characteristic train section are used to predict the noise inside the train in open field by using finite element method FEM, boundary element method (BEM) and statistical energy analysis (SEA) depending on the frequency range of analysis. The turbulent boundary layer excitation is implemented as the only airborne noise source, in order to focus on the study of the attached and detached flow in the surface of the train. The power spectral densities of the pressure fluctuation in the train surface proposed by [(Cockburn and Roberson 1974), (Rennison et al. 2009)] are applied on the exterior surface of the structural subsystems in the vibroacoustic models. An increase in the sound pressure level up to10 dB can be appreciated due to the detachment of the flow around the train. These results highlight the importance to determine the detached regions prediction, making critical the airborne noise due to turbulent boundary layer.
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9 Lee mas

COMPARATIVE ANALYSIS OF MEASUREMENT TECHNIQUES OF THE SOUND ABSORPTION COEFFICIENT OF A MATERIAL ANÁLISIS COMPARATIVO DE LAS TÉCNICAS DE MEDIDA DEL COEFICIENTE DE ABSORCIÓN SONORA DE UN MATERIAL

COMPARATIVE ANALYSIS OF MEASUREMENT TECHNIQUES OF THE SOUND ABSORPTION COEFFICIENT OF A MATERIAL ANÁLISIS COMPARATIVO DE LAS TÉCNICAS DE MEDIDA DEL COEFICIENTE DE ABSORCIÓN SONORA DE UN MATERIAL

Las tendencias actuales apuntan al desarrollo de nuevos materiales económicos y ecológicos con óptimas propiedades mecánicas, acústicas y térmicas. En la caracterización acústica del material es habitual medir su coeficiente de absorción sonora. Las dos técnicas usuales de medida de este parámetro son en cámara reverberante y en tubo de Kundt. No obstante, existen técnicas de medida “in situ” del coeficiente de absorción que permiten una comprobación del comportamiento real en la forma definitiva de colocación del material. En este trabajo se presenta un estudio comparativo del coeficiente de absorción sonora medido en un material usando distintas técnicas de medida.
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8 Lee mas

COMPUTED AIDED SEMIAUTOMATIC DETERMINATION, AT LABORATORY LEVEL, OF THE SOUND SPEED IN SOLIDS, LIQUIDS AND GASES

COMPUTED AIDED SEMIAUTOMATIC DETERMINATION, AT LABORATORY LEVEL, OF THE SOUND SPEED IN SOLIDS, LIQUIDS AND GASES

Table 3 present some results referring to some solids samples. The results dealing with steel, dural and PVC could be checked not only by two different frequency bands but also by two different sample length; the sound speed in those materials are very close to each other lying within the range error. In all the experiments the sampling frequency was 500 kHz. When working with fluids and gases the use of the system is very similar. The fluids fill specific receptacles, of different length, if necessary, figure 5. The enclosures were ended by two rubber like walls of 2.0 mm thick that will not introduce any significant error in the time measurement (the sound speed in the rubber like material is very close to that in water).
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7 Lee mas

COMPARISON BETWEEN SOUND REDUCTION INDEX MEASUREMENT TECHNIQUES

COMPARISON BETWEEN SOUND REDUCTION INDEX MEASUREMENT TECHNIQUES

With the sound intensity technique the sound power incident on the test specimen is determined by the sound pressure in the source room and the sound power transmitted is determined by direct measurement of the sound intensity through the test specimen. The latter measurement is independent of the flanking transmission from any path not enclosed in the measurement surface. Intensity measurements take into account both the structural and the airborne transmission through the partition wall and any other components of the partition (like leakages and air ducts). In laboratory conditions, intensity measurements should give results near those obtained with the traditional method.
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6 Lee mas

Determining the Wall Sound Absorption Coefficient of Assessed Anechoic and Semi-anechoic Rooms

Determining the Wall Sound Absorption Coefficient of Assessed Anechoic and Semi-anechoic Rooms

ABSTRACT: This work shows how the results from measurements made to assess the anechoic performance of anechoic and semi-anechoic rooms may be used to estimate the average sound absorption at the walls of these rooms and the room average absorption coefficient. An image model of the room anechoics has been made with which to predict the standard deviations from anechoic and semi-anechoic behaviour in a room of know absorption. Methods of assessing the acoustic performance of anechoic and semi-anechoic rooms have been implemented together with the image source model in order to process the data from measurements in a semi- anechoic chamber. Predictions of standard deviation and wall absorption were made for a semi-anechoic room of known characteristics. Room properties and measurement conditions are responsible for the relationship between the variability of sound pressure level and the wall average absorption coefficient. The agreement between numerical results and measurements is fairly good.
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8 Lee mas

Feasibility of a Simple Small Wind Turbine with Variable Speed Regulation Made of Commercial Components

Feasibility of a Simple Small Wind Turbine with Variable Speed Regulation Made of Commercial Components

turbine operation may be controlled without measuring the wind speed. Frequency converters have a very fast transient response. They can run the generator as a motor for start-up, and can quickly stop the turbine. Continuous power generation from zero to the highest turbine speed is possible. The line side power factor is unity with no harmonic current injection, and the inverter may be operated as a VAR/harmonic compensator when spare capacity is available [36,37]. As the generator is running at light loads most of the time, the machine rotor flux can be reduced from the rated value to reduce the core loss and thereby increase machine-converter system efficiency. Modern frequency converters have the option of inserting a built-in controller, to program the control strategies for optimal operation and maximum power and speed limits. The built-in programmable control unit could be also used to implement start-up techniques, or fine tune the optimum operational point tracking of the turbine, due to the variables such as air density, or changes in the turbine curve due to dirt or other factors. Finally, the generated energy can be supplied to the grid directly using a double-side frequency converter or a commercial regenerative braking unit connected to the converter DC link. The generated energy may either be consumed as DC, connecting the loads to the DC converter link, or may be stored in a battery bank.
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19 Lee mas

Consideration of tip speed limitations in preliminary analysis of minimum COE wind turbines

Consideration of tip speed limitations in preliminary analysis of minimum COE wind turbines

where F CR is the Fixed Charge Rate, ICC is the Initial Capital Cost, O&M are the Levelized Operations and Maintenance Cost, LRC is the Levelized Replacement/Overhaul Cost and LLC is the Land Lease Cost. All the terms in expression (6) are expressed, in the mentioned reference, as functions of the rated power, P R , rotor radius, R , and the ratio h/R . Additionally, some design

8 Lee mas

Natural vs. anthropogenic sources of hydrocarbons
				as revealed through biomarker analysis: A case study in the southern
				Gulf of Mexico

Natural vs. anthropogenic sources of hydrocarbons as revealed through biomarker analysis: A case study in the southern Gulf of Mexico

Biological markers are organic compounds in geological samples with an unambiguous link to specific precursor molecules in living organisms. They provide information on the origin and depositional environment of fossil organic matter as well as its thermal maturation caused by geothermal heat flow during burial. Petroleum and its refinery products carry this biomarker information into the environment when they are released during anthropogenically-induced pollution. Soils or aquatic surface sediments in contaminated area usually contain binary mixtures of fossil hydrocarbons and recent biogenic hydrocarbons like higher-plant wax esters, together with (often olefinic) hydrocarbons from earliest diagenetic transformation of functionalized biomolecules. Surface sediments collected in the shelf area of the Campeche Sound, Gulf of Mexico, sampled in the course of environmental monitoring for possible petroleum pollution due to industrial activity, however, revealed a third group of hydrocarbons. GC-MS analysis of biomarkers in the nonaromatic hydrocarbon fractions of the sediment extracts yielded overlapping hydrocarbon assemblages indicating multiple sources. Samples taken close to known asphalt seeps exhibit biomarker patterns virtually identical to those of reference crude oils. Other sediments contain mature fossil hydrocarbons and biomarkers typical of neither fossil fuels nor immature organic matter in marine surface sediments. They originate from drill cuttings recovered during penetration of Tertiary to Cretaceous deposits and discharged into the shallow sea.
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10 Lee mas

BRIEF REVIEW ON IN-SITU MEASUREMENT TECHNIQUES OF IMPEDANCE OR ABSORPTION

BRIEF REVIEW ON IN-SITU MEASUREMENT TECHNIQUES OF IMPEDANCE OR ABSORPTION

Standard procedures The traditional method to determine the sound absorption of a material is the standing wave tube. Details of different measurement procedures are described in internationals standards [12][18]. More details may be found in [19]. Another procedure to measure the sound absorption is based on Sabine`s reverberation formula and has been standardized in [20]. This indirect method may result in values for the sound absorption larger than 1. Various inter-laboratory comparisons have been carried out for this method [9][21][22][23].
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6 Lee mas

Financial performance analysis of Zakat management organization in Indonesia

Financial performance analysis of Zakat management organization in Indonesia

Este estudio tuvo como objetivo analizar el desempeño financiero de las organizaciones de gestión de zakat. La muestra de la aplicación de medición de informes de Internet es el sitio web de la Organización de Gestión de Zakat registrado en la Di- rección General de Regulación Fiscal No. PER-15 / PJ / 2012. Esta investigación utiliza un muestreo intencional que puede acceder al informe financiero por completo. El método de análisis de investigación utilizado es un análisis de contenido y medición del desempeño de la parte principal del desempeño financiero emitido por Indonesia Magnificence of Zakat (IMZ) en Indonesia Zakat Development Report (IZDR) 2011. La evaluación del desempeño financiero, en general, se considera Bastante bien.
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5 Lee mas

Analysis of Residual Stresses in High Speed Milled Aluminum Alloys

Analysis of Residual Stresses in High Speed Milled Aluminum Alloys

Figure 2 shows the state of residual stress at a point corresponding to the surface generated (point P). For obtaining the different components of stress for any point of such surface, eight micro-indents must be introduced. Each micro-indent pair corresponds to a corner of an imaginary square whose centroid is the point to be evaluated (Díaz and Mammana, 2012). In this study, the introduction of such micro-indents was performed using a high accuracy mechanical device, which is mounted on the UMM (Díaz et al., 2010). As previously mentioned, the micro-indent coordinates were measured, before and after a distension treatment (300°C and 80 min), using a UMM (GSIP MU-314). Then, through the processing of these coordinates (Mammana et al., 2010), it is possible to obtain the components of residual strain ε x , ε y and γ xy , which
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5 Lee mas

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