近场影响消除法测量声吸收系数

The method eliminating nearneld effect for measuring sound absorption coefficient

本文采用数值模拟方法理论研究了活塞式辐射器的辐射近场和采用“大”尺寸接收器接收对声场的平滑作用以及近场(及其过渡区域)对测量声吸收系数的影响.计算表明,在近场及其附近,用通常的方法测量声吸收系数将产生很大的误差.通过分析误差产生的原因,本文提出了近场影响消除法测量声吸收系数,并对a/λ=3、9,b=0、0.5a、a(a,b分别是辐射器和接收器半径)几种情况进行了数值模拟计算,结果表明,采用这种方法不仅能在近场区域进行测量,而且具有较高的测量精度.

As the strong coherence of the sound wave in nearfield of a projector , the pressure in the region is very complex. In addition, hydrophones in practical applications usually have a certain size of their receptive face, and maximum dimensions of the so called 'big' receiver may be many times the size of sound wave length. The pressure received by them is assembly pressure in loeal field, and will produce serious effect on results measured . In this paper, a numerical simulation method is used to study the radiation pressure field of a piston projector, smoothing effect on the field by the 'big' receiver and their influence on measurement of sound absorption coefficient in nearfield, and the nearfield effect setoff method (NESM) is advanced. The calculated results show that this method not only widens the measuring range in nearfield, but gives more accurate results.