Sound wave conduction

Sound wave conduction (Frohn et al., 1998), phacoemulsification performance and duration (Dick et al., 1996)... 

Ultrasonic Spectroscopy. Information on size distribution maybe obtained from the attenuation of sound waves traveling through a particle dispersion. Two distinct approaches are being used to extract particle size data from the attenuation spectmm an empirical approach based on the Bouguer-Lambert-Beerlaw (63) and a more fundamental or first-principle approach (64—66). The first-principle approach implies that no caHbration is required, but certain physical constants of both phases, ie, speed of sound, density, thermal coefficient of expansion, heat capacity, thermal conductivity. 

Schsilwelle, /. sound wave, schsilzuleitend, a. sound-conducting. 

The passage of a sound wave along a tube, so that no energy is dissipated by friction, is an example of a compressional wave of permanent type, and Newton applied his equation (1) to determine the velocity of sound in air. For this purpose he took e as the isothermal elasticity of air, which is equivalent to assuming that the temperature is the same in all parts of the wave as that in the unstrained medium. Since air is heated by compression and cooled by expansion, the assumption implies that these temperature differences are automatically annulled by conduction. Taking the isothermal elasticity, we have ... 

The pioneering work on the chemical applications of ultrasound was conducted in the 1920 s by Richards and Loomis in their classic survey of the effects of high frequency sound waves on a variety of solutions, solids and pure liquidsQ). Ultrasonic waves are usually defined as those sound waves with a frequency of 20 kHz or higher. The human ear is most sensitive to frequencies in the 1-5 kHz range with upper and lower limits of 0.3 and 20 kHz, respectively. A brief but useful general treatment of the theory and applications of ultrasound has been given by Cracknel 1(2). 

Relaxation methods can be classified as either transient or stationary (Bernasconi, 1986). The former include pressure and temperature jump (p-jump and t-jump, respectively), and electric field pulse. With these methods, the equilibrium is perturbed and the relaxation time is monitored using some physical measurement such as conductivity. Examples of stationary relaxation methods are ultrasonic and certain electric field methods. Here, the reaction system is perturbed using a sound wave, which creates temperature and pressure changes or an oscillating electric field. Chemical relaxation can then be determined by analyzing absorbed energy (acous-... 

It is sometimes useful to distinguish between conducting or dissipative media (crel > 0) and non-conducting media (cej = 0) For non-conducting media the velocity of an electromagnetic wave is proportional to (p.e)1/2, just as the velocity of a sound wave is proportional to the square root of the compressibility. 

The conventional macroscopic Fourier conduction model violates this non-local feature of microscale heat transfer, and alternative approaches are necessary for analysis. The most suitable model to date is the concept of phonon. The thermal energy in a uniform solid material can be jntetpreied as the vibrations of a regular lattice of closely bound atoms inside. These atoms exhibit collective modes of sound waves (phonons) wliich transports energy at tlie speed of sound in a material. Following quantum mechanical principles, phonons exhibit paiticle-like properties of bosons with zero spin (wave-particle duality). Phonons play an important role in many of the physical properties of solids, such as the thermal and the electrical conductivities. In insulating solids, phonons are also (he primary mechanism by which heal conduction takes place. 

Mechanical oscillations of >18,000 Hz are referred to as ultrasound. In solid bodies, sound waves spread longitudinally as well as transversally in fluids, gases or body tissue, however, waves only spread longitudinally. The average velocity of sound conduction (v) in tissues is approximately 1,500 m/sec. 

Ultrasonic waves are generated by a piezoelectric crystal and emitted via a sound-conductive medium. These waves are reflected, broken, dispersed and absorbed by boundary layers. The piezoelectric crystal also acts as a sound-wave receiver and registers the modified ultrasonic waves (= reciprocal piezoelectric effect). They are then converted into an electric signal and displayed by means of oscilloscopic imaging. 

Ultrasonic velocity has been almost exclusively measured in ultrasonic studies of fat crystallization, but the attenuation coefficient also can reveal interesting information. As the sound wave passes, the fluid is alternately compressed and rarefied which results in the formation of rapidly varying temperature gradients. Heat energy is lost because the conduction mechanisms are inefficient (thermal losses) and together with molecular friction (viscous losses) cause an attenuation of the sound given by classical scattering theory (5) ... 

The gas content of the liquid (nature, concentration), thermal conductivity, viscosity, temperature, hydrostatic pressure, frequency of the sound wave, and shape of the reactor. As a consequence the utmost care should be taken in monitoring experimental conditions to obtain good repeatability. 

A method used to calculate B(T) [7] (not favored by us, and presented here mainly for historical reasons) utilizes relationships between the bulk modulus B, the density p, and the velocity of acoustic (sound) waves in materials. B(T) is approximately equal to the product of the density with the sixth power of the ratio (UR/V), where UR is the molar Rao function (or the molar sound velocity function). UR is independent of the temperature. In the past, it has also been found to be useful in predicting the thermal conductivity (Chapter 14). 

The pressure geireration (fcscribed by Eqs. (27) and (28) in solution is finally to be detected by a piezoelectric transducer. Since the detector is not din tly introduced into solution in our expmments [18, 24], the sound wave must be conducted by difierent connecting materials to the piezoelectric detector and thus passes throuj various phase boundaries. The acoustic transition coefficient represents a measure for the crossing of the acoustic wave at these boundary surfaces [%, 97]. For the crossover of the sound wave from medium 1 into medium 2 we have ... 

Artificial ear implants capable of processing speech have been developed with electrodes to stimulate cochlear nerve cells. Cochlear implants also have a speech processor that transforms sound waves into electrical impulses that can be conducted through coupled external and internal coils. The electrical impulses can be transmitted directly by means of a percutaneous device. 

The electronic structure of rare-earth atoms with the configuration (Xe)4f"5d 6s gives rise to conduction bands with 5d and 6s character in the intermetallic compounds. The d bands can have a rather large density of states. Therefore the coupling of phonons to these itinerant electrons can be quite strong. In this chapter we review experimental effects caused by the interaction of conduction electrons with sound waves. These experiments mainly concern the anomalous temperature dependence of symmetry elastic constants and the presence of magnetoacoustic quantum oscillations observed in sound velocity and attenuation. 

Here i/ (z) = d In T(z) /dz is the digamma function and W is the band width of the Lorentzian conduction electron density of states. Furthermore, T) is the effective temperature-dependent coupling strength of the longitudinal sound waves to quasiparticles. It may be written as... 

Heat conduction into the gas phase causes a modulated expansion of a layer of gas near the sample surface, producing a sound wave that can be detected using a microphone the so-called photoacoustic effect. Thermally induced variations in the gas-phase... 

---