High frequency Ultrasonic transducer for finer mist making
From what research I found (99 page thesis) it appeared in 1986 that the most efficient transducer conductance to water was around 1.5MHz on page 71 . 

Therefore in answer to your question, I think not.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/17/083/17083027.pdf