Ultrasound dispersing unit - increasing power input with increasing pressure

[RDS12]

Hello,

I have a question pertaining to an ultrasound dispersing system.
The process consists of a tank with recycle... and along this process the flow stream comes into a tank where it is sonicated.
I can add pressure to the tank which causes the power input of the ultrasound to increase.

Can anyone help me understand why the added pressure causes the power input to increase?

Thanks in advance for the help.