Acoustics and Electroacoustics

Abstract

pp. Price 3. 40 rubles.Professor Lyamshev, the current editor of the Soviet Acoustics Journal, has long played a significant role in Soviet work on acoustooptics. In 1980, he contributed an invited paper on the subject to the ICA in Sydney, Australia. In this short volume, he carries out a careful exposition of the theoretical basis of laser excitation of sound, beginning with the simplest cases and proceeding systemically through the more complicated.The first chapter concerns itself with laser excitation of sound in a homogeneous half-space, first with a free surface and then with increasing complications of rough surfaces. Chapter 2 takes up various possible materials in the second half-space, be it another liquid, a solid, or an inhomogeneous surface layer. Here, he also introduces FM modulation of the intensity of the exciting laser.Chapter 3 continues this exploration of the source, considering pulses of various shape, interactions in one and three dimensions, and the effect of bubbles on the sound generation.The effect of moving sources has been of interest in Soviet acoustics since the days of Blokhintsev in the late 40s, and Chap. 4 is devoted to effects produced by moving laser thermooptical sound sources. The theoretical analysis is then completed by a chapter on the laser generation of sound in solids, including surface wave excitation and solid waveguides.The last chapter in the book is devoted to experimental results, mainly for laser-induced sound in water, with a small amount of attention paid to excitations of surface acoustic waves in solids.

Acoustic transmission line metamaterial with negative/zero/positive refractive index

“…This section describes the adopted conventions associated with this formalism when used for acoustic waves in a fluid and introduces the concept of TL-based metamaterial. In the acoustic circuit modeling used in this work, the voltage corresponds to the acoustic pressure p and the current to the volume velocity q flowing through a surface S. This representation is often used for waveguide related problems, where S is naturally the waveguide cross-sectional area, 29,30 but it can also be applied to plane waves in an unbounded medium, in which case S can be chosen arbitrarily.…”

“…The membrane is modeled as a thin plate described by the transverse displacement ͑r͒, which satisfies the flexural waves equation 29,33,34 …”

“…Assuming a uniform pressure field on the membrane, the effect of the latter on the acoustic field can be represented by the acoustic impedance Z am defined as 29,34 …”

“…The considered stub is physically open at its termination, which approximately corresponds to a condition p =0. 29 As a result, the stub is approximately short circuited according to the chosen TL modeling, hence the name "shorted stub" that will be used thereafter.…”

“…6͑b͒ by adding an acoustic resistance R at in series with the acoustic mass m at . Based on the HagenPoiseuille assumption of laminar viscous fluid, the R at for a short radial stub can be approximated at low frequency by 29,34 …”