Acoustic properties propagation

The elastic properties of PS depend on its microstructure and porosity. The Young s modulus for meso PS, as measured by X-ray diffraction (XRD) [Ba8], acoustic wave propagation [Da5], nanoindentation [Bel3] and Brillouin spectroscopy [An2], shows a roughly (1-p)2 dependence. For the same values of porosity (70%), micro PS shows a significantly lower Young s modulus (2.4 GPa) than meso PS (12 GPa). The Poisson ratio for meso PS (0.09 for p=54%) is found to be much smaller than the value for bulk silicon (0.26) [Ba8]. 

Heat is the most common product of biological reaction. Heat measurement can avoid the color and turbidity interferences that are the concerns in photometry. Measurements by a calorimeter are cumbersome, but thermistors are simple to use. However, selectivity and drift need to be overcome in biosensor development. Changes in the density and surface properties of the molecules during biological reactions can be detected by the surface acoustic wave propagation or piezoelectric crystal distortion. Both techniques operate over a wide temperature range. Piezoelectric technique provides fast response and stable output. However, mass loading in liquid is a limitation of this method. 

The ability to use SAW devices for real-time monitoring of corrosion of thin metal films in gaseous environments has been demonstrated. Metal films, ranging in thickness from a few Angstroms to a micron, were deposited on the prop-agatimi path between transducers. Since the acoustic-wave propagation velocity depends upon the mass and mechanical properties of the film, any change in these properties due to corrosion alters the velocity. 

Which sediment property mainly influences the ultrasonic acoustic wave propagation (50 - 500 kHz), and how affects it the P-wave velocity and attenuation in terrigenous and calcareous sediments ... 

QCM can be described as a thickness-shear mode resonator, since weight change is measured on the base of the resonance frequency change. The acoustic wave propagates in a direction perpendicular to the crystal surface. The quartz crystal plate has to be cut to a specific orientation with respect to the ciystal axis to attain this acoustic propagation properties. AT-cut crystals are typically used for piezoelectric crystal resonators[7]. The use of quartz crystal microbalances as chemical sensors has its origins in the work of Sauerbrey[8] and King [9] who... 

These effects lead to SAW phase velocity local changes determining sensor output. For SAW propagating along x axis, the relationship between SAW phase velocity V relative and changes of the layer acoustic properties is [2]... 

Acoustic baffles are used to reduce the transmission of this noise into sensitive areas, including the upper body structure, where acoustical breakout (noise penetration) through drain and access holes in the body are attenuated only by the acoustical properties of the interior trim components. The variety of potential paths by which sound is propagated throughout the upper body structure requires the baffle package design be evaluated as a system for acoustic and water management. 

In literature (25-30) it is anticipated that i) the concept of the LMGP can be extended to acoustic waves propagating in liquids, ii) the LMGP varies only slightly in a given phase, and iii) the LMGP of a liquid still reflects the anharmonic properties of the material. 

Associated with each of the two modes of propagation, there is a sound speed and an absorption. Thus, four parameters are required to specify the acoustic properties of a solid isotropic polymer longitudinal speed, shear speed, longitudinal absorption, and shear absorption. 

Perhaps the most general mathematical treatment of the surface mass loading effect on bulk shear wave resonators has been presented by Kanazawa (13). In this work, a wave equation was developed for acoustic wave propagation within the deposited layer, assuming the material had both elastic and viscous properties. Boundary conditions between crystal and deposited mass were established by assuming shear forces and particle displacements were equal for both materials at the interface plane. This approach results in a fairly complex mathematical model, but simplified relationships were derived for purely elastic and purely viscous behaviour. 

This type of sensor operates by observing the propagation of an acoustic wave through the solid-state device. Sensing is achieved by correlating acoustic wave-propagation variations to the amount of analyte captured at the surface and then to the amount or concentration of analyte present in the sample exposed to the sensor, or to the changes in physical properties of interfacial thin films. 

This chapter first provides an introduction to the acoustic properties of textiles, which include propagation, absorption, and scattering of sound. The properties can be characterized by various parameters such as flow resistance, transmission loss, absorption coefficient, and scattering coefficient. Test and evaluation methods for obtaining these parameters are discussed. Based on the acoustic properties of the textiles, acoustics designers can make use of textiles in buildings and office environments to optimize sound quaUty depending on particular requirements. 

Most textiles that are used for acoustic purposes show open porosity due to many interconnected pores or voids inside. The acoustic performance of a porous textile is mainly determined by its (air) flow resistivity, which is an intrinsic property of the textile and is a measure of how easily air can enter and pass through a porous textile material (Cox and D Antonio, 2009). Flow resistivity, also known as static flow resistivity, is related to acoustical properties and plays a critical role in the calculation of many intrinsic acoustic properties of porous textiles, such as the characteristic impedance, the propagation constant, and the sound absorption coefficient. In the S.l. Unit system, flow resistivity is quoted in units of Nsm" and is defined as the unit-thickness specific flow resistance o (Morfey, 2001),... 

Results relating to individual bubble dynamics were used in theory of soimd propagation in two-phase viscoelastic hquids and later for modeling the acoustic properties of elastic tubes with polymeric liquids, containing microbubbles. " ... 

Acoustic properties (i.e., reflection coefficient, attenuation, and velocity of acoustic wave), and surface condition (i.e., surface roughness and discontinuities) of the specimen are factors in forming acoustic images. For a nanoscaled thin film system, (1) deference in the velocity of the surface acoustic wave propagating through the portion of the system and (2) increase of the amplitude of the acoustic wave caused by returning of the acoustic wave from the discontinuity located within the system are important for contrast factor. 

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