Speed of sound

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Thermodynamics of amide + ketone mixtures  2  Volumetric, speed of sound and refractive index data for N,N dimethylacetamide + 2 alkanone systems at several temperatures  Application of Flory's model to tertiary amide + n alkanone systems

Thermodynamics of amide + ketone mixtures 2 Volumetric, speed of sound and refractive index data for N,N dimethylacetamide + 2 alkanone systems at several temperatures Application of Flory's model to tertiary amide + n alkanone systems

Binary mixtures have been prepared by mass in small vessels (  10 cm 3 ) using an analytical balance Sartorius MSU125p (weighing accuracy 0.01 mg), with all weighings corrected for buoyancy effects. The standard uncertainty in the final mole fraction is estimated to be 0.0001. Molar quantities were determined on the basis of the relative atomic mass Table of 2015 issued by the CIAAW (IUPAC) [23]. Temperatures were measured by means of Pt-100 resistances. Their calibration was conducted according to the ITS-90 scale of temperature, against the triple point of the water and the fusion point of Ga. The standard uncertainty of the equilibrium temperature measurements is 0.01 K and 0.02 K. for  and n D measurements, respectively. A vibrating-tube densimeter and sound analyser DSA5000 from Anton Paar, automatically thermostated within 0.01 K, has been used for the measurements of  and c values. Details about the device calibration can be found elsewhere [24]. The repeatability of the  measurements is 0.005 kg·m -3 , whereas their overall uncertainty is 110 -2 kgm -3 . Speed of sound is determined measuring the time of propagation of short acoustic pulses (central frequency, 3 MHz) [25], transmitted repeatedly through the sample. The repeatability of the c measurements is 0.1 m·s -1 and their standard uncertainty is 0.2 m·s -1 .
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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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Adaptación de un tubo de Kundt para la determinación de la velocidad del sonido a distintas temperaturasSet up of a kundt’s tube to obtain the speed of sound at different temperatures

Adaptación de un tubo de Kundt para la determinación de la velocidad del sonido a distintas temperaturasSet up of a kundt’s tube to obtain the speed of sound at different temperatures

In this work we describe how we designed and built an acoustic system that allowed us to adapt a Kundt’s tube for the measurement of the speed of sound at different temperatures. The air column inside the tube was excited by a speaker at a frequency of 2 kHz. We changed the air column length by moving a piston throughout the tube, and we measured and recorded that length when we observed a resonance signal on the oscilloscope screen. This procedure was repeated at different temperatures, ranging from 19 ○ C to

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NONLINEAR SOUND REVERBERATION IN ENCLOSURES

NONLINEAR SOUND REVERBERATION IN ENCLOSURES

When dealing with nonlinear sound waves it is quite common to maintain the speed of sound as a constant [5], and later we will use this hypothesis, though at high nonlinear levels the sound speed is higher than within lineal range [6], [7], and causes among other effects distortion of nonlinear sound waves. It is also known since Sedov [7] that sound level decreases with distance to sound source at rates higher than within linear range. At very high nonlinear ranges it is admitted a level attenuation well above the linear range: 1/r 6 for atomic explosions, for instance, compared to 1/r 2 for linear range, due to simple spherical divergence.
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ACOUSTICAL ANALYSIS OF PIPES WITH FLOW USING INVARIANT FIELD FUNCTIONS

ACOUSTICAL ANALYSIS OF PIPES WITH FLOW USING INVARIANT FIELD FUNCTIONS

Acoustic waves in pipes below first cut-on frequency are analyzed. Three invariant functions of the internal acoustic pressure field are evaluated. These functions allow for the determination of the following quantities: spatial mean RMS value of pressure spectrum, lower and upper bounds of the pressure spectrum for the entire pipe, pressure spectrum at an arbitrary position, speed of sound in the contained fluid and fluid flow velocity.

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DEPENDENCE OF THE DIRECT SOUND ENERGY UPON THE DISTANCE TO THE SOUND SOURCE

DEPENDENCE OF THE DIRECT SOUND ENERGY UPON THE DISTANCE TO THE SOUND SOURCE

Direct sound was used by Ch.A. Shchirzeckij [1] for the studies of critical distance at which the direct sound energy is equal to the diffusive sound energy. He investigated the isotropy of sound field in five directions, measuring only the sound pressure in three octave bands. Direct sound was used for the critical distance studies by J. Mourjopoulos [2], J.Jetz [3], T. Gorne [4], and W. Reichardt [5] .

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Speed of pulled fronts with a cutoff

Speed of pulled fronts with a cutoff

where the reaction term f共u兲 is a nonlinear function with at least two fixed points, one stable and one unstable. Without loss of generality we assume that there is an unstable fixed point at u = 0 and a stable fixed point at u = 1. The reaction term f 共 u 兲 obeys additional requirements depending on the phenomenon under study. In the present work we shall be interested in two generic classes. The first class, which we label type A, is that for which f ⬎ 0 in 共0,1兲, the second class, type B, also called the combustion case, is that for which f = 0 in 共0 ,a兲, and f ⬎ 0 in 共a , 1兲. It was proven by Aronson and Weinberger 关 1 兴 that sufficiently localized initial condi- tions evolve into a monotonic front joining the stable to the unstable state. In case B there is a unique speed for which a monotonic front exists. In case A, the front propagates with the minimal speed for which monotonic fronts exist. This minimal speed satisfies
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ANALYSIS OF A SOUND SPEED MEASUREMENT MADE IN 1738

ANALYSIS OF A SOUND SPEED MEASUREMENT MADE IN 1738

They used as clocks pendulums protected against the wind. It was thought to make five shots. The three first in the direction to Ulloa and Bouguer. The fourth one in the direction to Jorge Juan and Godin. In the last shot the cannon would be placed vertically. With respect to the meteorological conditions, we only know that in the Panecillo peak and the position of Ulloa and Bouguer there was not wind. From the position of Jorge Juan and Godin the wind speed was opposite to the propagation of the sound, with an approximate value of 2 Toesas per second. Jorge Juan also comments in his report that, rigurously, the light speed should be accounted too, to evaluate the time that light took to arrive to them, but in practice, they assumed the light speed as infinitum, quoting the work of Roemer about the observation of the Jupiter satellites.
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Homogeneization effects of variable speed limits.

Homogeneization effects of variable speed limits.

The methodology is based on a before & after evaluation, by observing the evolution of the PAA indicator. Ideally, the number of trip repetitions should be fairly high in order to limit variations caused by other factors such as meteorology, extraordinary events, incidents, etc. In any case, the trips must be made in the same time slot and on days with similar behaviour in terms of traffic. In the event of a limited sample, particular care must be taken to ensure that the conditions are almost the same. The traffic intensity upstream must be guaranteed to be substantially the same when performing the before & after trips.
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Use of SEA to Model the Sound Field in Large Acoustic Spaces

Use of SEA to Model the Sound Field in Large Acoustic Spaces

Computer models based on mathematical methods developed according the principles of the Image Source Method [4], or Ray Acoustics techniques [5] or even radiosity method [6] have proven to be more accurate – [7] makes a comparative study between the Complete Image Source Method (CISM) and two other empirical methods: Hodgson and Heerema models where it is shown that CISM generally provides better results that the other two models tested. Ray tracing technique has the advantage of easily representing enclosed spaces of arbitrary shape, facilitating the modelling of internal walls, barriers or pitched roofs. Particularly interesting are the works developed by Hodgson, [8] and [9], applying this technique to some practical situations.
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PSYCHOACOUSTICS – IMPORTANCE AND APPLICATION IN PRACTICE

PSYCHOACOUSTICS – IMPORTANCE AND APPLICATION IN PRACTICE

Sound quality can be defined as the degree to which the totality of the individual requirements made on an auditory event are met. Acoustic quality comprises three different kinds of influencing variables: physical (sound field), psychoacoustic (auditory perception), and psychological (auditory evaluation) and therefore is a multidimensional task as shown in Fig. 1. Physical and psychoacoustic measurement procedures alone do not allow a general and unequivocal definition of acoustic quality. This is because listeners primarily classify perceived auditory events in terms of their experience, expectations and subjective attitudes. Although the term "noise" has been clearly defined in DIN 1320 (”Noise is sound occurring within the frequency range of human hearing which disturbs silence or an intended sound perception and results in annoyance or endangers the health”), no such type of definition can be given for the term ”sound quality” or „acoustic quality“.
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EFFECTS OF MEANING OF SOUND ON LOUDNESS JUDGEMENTS

EFFECTS OF MEANING OF SOUND ON LOUDNESS JUDGEMENTS

If loudness judgments depend only on the psychoacoustic magnitude loudness, then loudness judgments of the original sound and those of the synthetic sound neutralized by Fastl’s procedure should not significantly differ. Between the pink noise and the original sound, however, a difference is to be expected. If meaning does have an effect, however, then loudness judgments of original noise and the FTT-processed noise should reveal significant differences. Because of the lack of literature reporting respective findings we have no hypotheses of the way in which such differences caused by meaning would occur. Does meaning affect judgments in a general way, or are judgments affected in a specific way by certain meanings? Moreover, meaning not only might by dependent on objects but also upon the individual subject and the context. Because no well-founded specific hypotheses can be made, our experiment is part of a pilot study.
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Sound

Sound

We have already talked about what sound is and why it could powerfully affect human body and soul. But how could sound produce these effects? I think we have to find the possible answers in music. On the one hand, music treatises from the end of the fifteenth to early seventeenth centuries usually emphasized the correlation of each of the modes (scales formed by a distinctive distribution of their sounds) with a particular ethos (Gaffurius 1492, 1496). Although it was very far from its original concep- tion, such a Greek term generally shows the belief, shared by many Medieval and Renaissance scholars, that music can carry, enact, or even impose a specific mood on human beings. As the Renaissance tradition was by no means system- atic, let us see as an example the conception of the third and four modes, Phrygian and Hypo- phrygian, as established by Spanish theorist Bartolomé Ramos de Pareja (1990). The Phrygian mode, which is associated by Ramos de Pareja with the yellow bile, increases cruelty and anger. By contrast, music composed in the Hypo- phrygian mode weakens it and so on for each mode, which, in Ramos de Pareja’s theory, were also linked to planets, colors, and muses.
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ON MODELLING OF ROOM ACOUSTICS BY A SOUND ENERGY TRANSITION APPROACH

ON MODELLING OF ROOM ACOUSTICS BY A SOUND ENERGY TRANSITION APPROACH

In this paper, an alternative geometrical-statistical method is presented, describing a simple technique with low computation times, for a very wide range of room geometry configurations [1]. The sound field inside the enclosures is considered to be contributed by discrete energy packets, that are radiated from one, or several, sources. The motion of these energy packets, or sound particles, or phonons, is completely determined by an equation of motion that considers the transition amplitudes, when the sound particle changes its location inside the enclosure. Physical phenomena such as sound absorption in the air and in the surface walls are accounted for.
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Relationship between objective and subjective indicators in urban soundscape analysis. The case of Cordoba - Argentina

Relationship between objective and subjective indicators in urban soundscape analysis. The case of Cordoba - Argentina

Various works implement field surveys to determine the comfort level of users of the analyzed outdoor spaces. Questionnaires based on open and closed questions are directed to general sociological and individual aspects in relation to the physical space to be assessed, and the characterization of its soundscape. The questionnaire applied in the context of this work has taken as a general reference the one developed in an european project [5]. It contains a structure with initial questions intended to characterize the user’s sociological profile, then the overall assessment of the landscape of analyzed urban space and finally the characterization of sound sources and the degree of discomfort. Following the criteria established in similar works, the application of semantic scales of a maximum of five categories was adopted for the characterization [3] [6].
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SOUND-DESIGN DEVELOPMENT WITH SOUND SIMULATION VEHICLE

SOUND-DESIGN DEVELOPMENT WITH SOUND SIMULATION VEHICLE

The base function of humans sense of hearing is to gather information out of their environment and to use it for different purposes. The acoustical stimulus is represented by the collected sound waves. These sound waves, collected by the ears, include all acoustical information of interest. In other words the sound that may be measured with an artificial head for example contains all physical information as far as only the hearing system is concerned. According to Fig. 1 all sensorial information with regard to acoustics, e.g. intensity, frequency spectrum, time structure, stimulus statistics, number and arrangement of sources etc. are considered (acoustical level I and II) in that kind of recordings.
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Aspects of Hearing in Diffuse Sound Fields

Aspects of Hearing in Diffuse Sound Fields

Let us now turn the attention to the CCC. When the CCC is calculated using measurements performed at the entrance of the ear canals the first CCC zero occurs at approximately 500Hz, compared to approximately 1200Hz when the CCC is measured at the interaural distance but without the head in-between (Figure 4). The second zero crossing occurs at approximately 1000Hz. In between the CCC takes negative values. Therefore, in the range of frequencies where the CCC (measured with head) takes positive values there is a peak of the NCCF at τ =0.0 ms and in the range where the CCC takes negative values there are two NCCF peaks symmetric to τ =0.0 ms (Figure 2). The latter is a very interesting result as it may contribute to the explanation of the lateral concentration of the auditory events previously reported. It is important to note that the absence of a (negative) peak of NCCF at τ = 0.0 ms for the 500 Hz - 1000 Hz range is related to the halfwave rectification neural transduction model applied in the present study.
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8 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

A relation between Cost Of Energy, COE , maximum allowed tip speed, and rated wind speed, is obtained for wind turbines with a given goal rated power. The wind regime is characterised by the corresponding parameters of the probability density function of wind speed. The non-dimensional characteristics of the rotor: number of blades, the blade radial distributions of local solidity, twist angle, and airfoil type, play the role of parameters in the mentioned relation. The COE is estimated using a cost model commonly used by the designers. This cost model requires basic design data such as the rotor radius and the ratio between the hub height and the rotor radius. Certain design options, DO, related to the technology of the power plant, tower and blades are also required as inputs. The function obtained for the COE can be explored to nd those values of rotor radius that give rise to minimum cost of energy for a given wind regime as the tip speed limitation changes. The analysis reveals that iso-COE lines evolve parallel to iso-radius lines for large values of limit tip speed but that this is not the case for small values of the tip speed limits. It is concluded that, as the tip speed limit decreases, the optimum decision for keeping minimum COE values can be: a) reducing the rotor radius for places with high weibull scale parameter or b) increasing the rotor radius for places with low weibull scale parameter.
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STUDIES ON IMPACT SOUND INSULATION OF FLOORS

STUDIES ON IMPACT SOUND INSULATION OF FLOORS

Spectrum adaptation terms do not bring out any surplus value when rating concrete floors. The use of the spectrum adaptation term calculated at lower frequencies (calculated from 50 Hz) brings out a noticeable difference between heavy weight and lightweight floors (on the average about 3 dB impairment). On the other hand, extending of the measurements to frequencies 50, 64 and 80 Hz may contain serious problems. The use of a standard tapping machine at low fre- quencies to describe real heavy impacts may be doubtful.

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Chapter 02

Chapter 02

Q2.6 We assume the object moves along a straight line. If its average velocity is zero, then the displacement must be zero over the time interval, according to Equation 2.2. The object might be stationary throughout the interval. If it is moving to the right at first, it must later move to the left to return to its starting point. Its velocity must be zero as it turns around. The graph of the motion shown to the right represents such motion, as the initial and final positions are the same. In an x vs. t graph, the instantaneous velocity at any time t is the slope of the curve at that point. At t 0 in the graph, the slope of the curve is zero, and thus the instantaneous velocity at that time is also zero.
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