Discriminating between the nearfield and the farfield of acoustic transducers
Discriminating between the nearfield and the farfield of acoustic transducers
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DOI：
10.1121/1.4895701
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发表时间：
2014-10-01
影响因子：
2.4
通讯作者：
Foote, Kenneth G.
中科院分区：
文献类型：
--
作者：
Foote, Kenneth G.
声换能器的性能的测量以及利用声换能器进行的普通测量可能需要区分远场和互补近场，在远场中，场是球面发散的，在互补近场中，场结构更复杂。研究了一个安装在无限大平面刚性挡板上的具有均匀法向速度分布的平面圆形活塞投影器。通过误差为20 log的竖条p（f）/p（n）竖条，将向内外推的远场压力幅度p（f）与由瑞利积分建模的精确近场压力幅度p（n）进行比较。对波数-半径乘积ka = 10的活塞进行了三组计算：在对应于波束图损失为0、10、20和30 dB的角度处的归一化压力幅值和误差与范围的关系;在三个范围处的误差与角度的关系，a（2）/lambda、pia（2）/lambda和10 a（2）/lambda，其中lambda是波长;和范围与角度的两个向内有界的错误，1和0.3分贝。通过互易性，结果同样适用于在活动表面上具有均匀灵敏度的带挡板的圆形活塞接收器的情况。建议通过类似的建模建立与圆形活塞相关的场的测量的接近准则，并且在计算误差的基础上将品质因子分配给测量。(C)2014年美国声学学会。
Measurements of the performance of acoustic transducers, as well as ordinary measurements made with the same, may require discriminating between the farfield, where the field is spherically divergent, and the complementary nearfield, where the field structure is more complicated. The problem is addressed for a planar circular piston projector, with uniform normal velocity distribution, mounted in an infinite planar rigid baffle. The inward-extrapolated farfield pressure amplitude p(f) is compared with the exact nearfield pressure amplitude p(n), modeled by the Rayleigh integral, through the error 20 log vertical bar p(f)/p(n)vertical bar. Three sets of computations are performed for a piston with wavenumber-radius product ka = 10: normalized pressure amplitudes and error versus range at angles corresponding to beam pattern losses of 0, 10, 20, and 30 dB; error versus angle at three ranges, a(2)/lambda, pi a(2)/lambda, and 10a(2)/lambda, where lambda is the wavelength; and range versus angle for each of two inward-bounded errors, 1 and 0.3 dB. By reciprocity, the results apply equally to the case of a baffled circular piston receiver with uniform sensitivity over the active surface. It is proposed that proximity criteria for measurements of fields associated with circular pistons be established by like modeling, and that a quality factor be assigned to measurements on the basis of computed errors. (C) 2014 Acoustical Society of America.