设计并搭建了超声光栅，观察了激光经过光栅形成的衍射斑纹，测量了声速; 并利用超声光栅测定了不同温度、不 同浓度的NaCl 溶液中的声速，给出了声速-水温和声速-溶液浓度的依赖关系. 水的温度每升高1℃，3.974 MHz 的超声波的 声速增加2.09 m/s， 16.574 MHz 的超声波的波速增加2.04m/s; 声速随着NaCl 溶液浓度的增大线性增加，NaCl 溶液浓度每升 高1%，3.974 MHz 的超声波声速增加13.637 m/s， 16.574 MHz 的声波声速增加11.757 m/s.在此基础上，分析了不同频率的超 声波对实验规律的影响，认为不同频率的超声波在相同条件下测量的溶液中声速大小的不同源于测量的随机误差.

Ultrasonic grating is design and built.Clear diffraction spots are obtained while a laser beam passes through. By measuring the distance between spots，the velocity of sound iscalculated and analyzed. Furthermore，the velocity of sound in pure water with different temperatures and Nacl solution with different concentrations are measured. Dependence of the sound velocity on the temperature and liquid concentration is established. T velocity of sound increases linearly with temperature and liquid concentration. The velocity increases 2.09m/s for 3.974MHz wave，and 2.04m/s for 16.574MHz wave when the temperature increases for 1℃. The velocity of sound increases 13.6m/s for 3.974MHz wave，and 11.8 m/s for 16.574MHz wave as the concentration of NaCl solution increases 1%. The difference in velocity of sound with different frequency is ascribed to inaccuracy of measurement.