The infinite planar baffles problem in acoustic radiation and its experimental verification

Abstract

In acoustics, the analysis of pressure distribution in a field of surface sources is most frequently performed using the assumption that the source constitutes a part of an infinite planar rigid baffle (Rayleigh’s approximation). However, in many practical cases of ultrasonic echography, assumption of a soft pressure-release baffle (the Rayleigh-Sommerfeld approximation) or of free-field conditions (the Kirchhoff approximation) seemed to be better matched to real conditions. A theoretical survey of the planar baffles problem is given in this paper, and its practical aspects in acoustic source radiation are discussed. Some experiments, showing the influence of different boundary conditions onto radiation patterns, verify the theoretical predictions.

A computational method to calculate the longitudinal wave evolution caused by interfaces between isotropic media

“…A detailed general deduction of (4), (5), and (6) is shown in Appendix A, considering that the infinite baffle around the interface can be one of the three basic types of boundary conditions: rigid, soft, and free-field [25]. This model neglects field components, which appear at a fluid/solid interface, like the converted waves, shear waves, surface waves, head waves, etc.…”

“…In particular, the obliquity factors for rigid, soft, and free-field boundary conditions analyzed by Delannoy et al [25] are:…”

Directivity and Frequency-Dependent Effective Sensitive Element Size of Needle Hydrophones: Predictions From Four Theoretical Forms Compared With Measurements

“…The second form for directivity uses the assumption of a circular piston in a soft (pressure-release) baffle (SB), which involves multiplication of the RB form by cos θ [28]. $$D_{SB}(k,\theta )=\frac{2J_1(kasin\theta )}{kasin\theta }cos\theta$$ The third form uses the assumption of an unbaffled (UB) circular piston, which involves multiplication of the RB form by (1 + cos θ )/2 [29]. $$D_{UB}(k,\theta )=\frac{2J_1(kasin\theta )}{kasin\theta }\left(\frac{1+cos\theta }{2}\right)$$…”

Modeling the acoustic field of physiotherapy ultrasound transducers using non uniform acoustic pressure distributions

“…it is feasible the complete interchange of energy between the front medium and the back one. In ultrasonic imaging, each element is fixed with acoustically soft material, and hence a soft baffle condition must be applied in this modeling [7,8]. For this paper, only rigid baffles are considered because this condition is dominant for physiotherapy transducers [8].…”