Harland Andy R, Petzing Jon N, Tyrer John R
Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom.
J Acoust Soc Am. 2004 Jan;115(1):187-95. doi: 10.1121/1.1635841.
Localized changes in the density of water induced by the presence of an acoustic field cause perturbations in the localized refractive index. This relationship has given rise to a number of nonperturbing optical metrology techniques for recording measurement parameters from underwater acoustic fields. A method that has been recently developed involves the use of a Laser Doppler Vibrometer (LDV) targeted at a fixed, nonvibrating, plate through an underwater acoustic field. Measurements of the rate of change of optical pathlength along a line section enable the identification of the temporal and frequency characteristics of the acoustic wave front. This approach has been extended through the use of a scanning LDV, which facilitates the measurement of a range of spatially distributed parameters. A mathematical model is presented that relates the distribution of pressure amplitude and phase in a planar wave front with the rate of change of optical pathlength measured by the LDV along a specifically orientated laser line section. Measurements of a 1 MHz acoustic tone burst generated by a focused transducer are described and the results presented. Graphical depictions of the acoustic power and phase distribution recorded by the LDV are shown, together with images representing time history during the acoustic wave propagation.
声场的存在所引起的局部水密度变化会导致局部折射率的扰动。这种关系催生了许多用于记录水下声场测量参数的非扰动光学计量技术。最近开发的一种方法涉及通过水下声场将激光多普勒振动计（LDV）对准一块固定的、不振动的平板。沿着线段测量光程长度的变化率能够识别声波波前的时间和频率特性。通过使用扫描LDV，这种方法得到了扩展，它有助于测量一系列空间分布参数。本文提出了一个数学模型，该模型将平面波前中的压力振幅和相位分布与LDV沿着特定取向的激光线段测量的光程长度变化率联系起来。描述了由聚焦换能器产生的1 MHz声脉冲串的测量，并给出了结果。展示了LDV记录的声功率和相位分布的图形描绘，以及表示声波传播过程中时间历程的图像。
