| 摘要 |
<p>A liquid column (2) is placed between two high-frequency ultrasound sources (6) in the field of a standing wave produced by the sources. Each source produces a convergent beam that compensates for a substantial part of the attenuation of the ultrasound energy that occurs at higher frequencies. It is thereby possible to increase considerably the axial distance along the standing wave over which streaming effects due to acoustic pressure are absent or negligible. It is also possible to increase the angle of convergence to compensate for divergence of the outputs from the sources.</p> |
