Harmonic generation in finite amplitude sound beams from a rectangular aperture source

Abstract

Theoretical analysis and some experiments are performed on nonlinearly generated harmonic components in bounded sound beams emitted from a rectangular aperture source. The Khokhlov–Zabolotskaya–Kuznetsov equation, which takes account of nonlinearity, dissipation, and diffraction effects in the beams, is numerically solved by means of the alternating direction implicit difference method. Using a planar source of size 24×44 cm, axial sound pressures and beam patterns of the first three harmonics are measured in air for initially sinusoidal ultrasounds of 25- and 30-kHz frequency, and are compared with the theory. They are in relatively good agreement. Deformation of the source face from circular to rectangular shape results in the unclear appearance of pressure peaks and dips with propagation. Within the framework of these studies, the harmonic pressure levels in the far field are almost the same as from a circular aperture source with equal face area and equal initial pressure, independent of the source levels.

Generating dual beams from a single steerable parametric loudspeaker

“…the notable harmonic distortion [10] and relatively weak bass output [11]. Research works on preprocessing methods have been extensively carried out to address the harmonic distortion [12][13][14][15]. On the other hand, the bass output of the parametric loudspeaker is an inevitable result of the parametric acoustic array.…”

Increased off-axis energy deposition due to diffraction and nonlinear propagation of ultrasound from rectangular sources

“…While beams due to circular transducers have been studied in some detail ͑see, for example, Refs. 3-8͒, it is only recently that models have been developed, 9,10 that are capable of predicting the nonlinear evolution of beams lacking cylindrical symmetry, partly due to the demands they place on the computer, and partly to the need for reliable algorithms. 11 Yet real ultrasound scanners now usually involve a rectangular phased array of rectangular elements.…”

Focused ultrasound actuation of shape memory polymers; acoustic-thermoelastic modeling and testing

“…The method originally designed for monochromatic waves and tone bursts, was later modied to include the calculations for far eld, 72 focused beams 56 and nonaxisymmetric sources. 73 In order to overcome the problem of high computational time required for solving nonlinearity term with spectral method, hybrid method was adopted by several researchers. 74,75 The hybrid method based on KZK equation solves for the effects of absorption and diffraction in frequency domain and of nonlinearity in time domain.…”