Photoacoustic excitation of a fluid sphere generates an outgoing ultrasonic wave whose time profile permits determination of the density, sound speed, and diameter of the sphere. Experiments with pulsed laser beams have confirmed the major predictions of existing theory. With regard to acoustic waves generated within spheres, although mathematical expressions for their properties are known, virtually no exploration of the waveforms in theory or experiment has taken place. Here, two cases for photoacoustic excitation of a droplet are discussed: first, absorption of radiation in a region of fluid external to the droplet, and, second, absorption of radiation by the droplet itself. Large amplitude transients, compressions in the former and rarefactions in the latter, are generated as the waves approach the center of the sphere. The high amplitudes of the waves suggest shock wave formation.

流体球体的光声激发会产生一个传出超声波，其时间分布允许确定球体的密度、声速和直径。脉冲激光束实验证实了现有理论的主要预测。关于在球体内产生的声波，虽然其性质的数学表达式是已知的，但实际上没有在理论或实验上对波形进行探索。在这里，讨论了液滴的光声激发的两种情况：首先，液滴外部流体区域中辐射的吸收，其次，液滴本身对辐射的吸收。当波接近球体中心时，会产生大振幅瞬变，前者为压缩，后者为稀疏。