Justb a point of interest here but I have come across industrial sonic cleaners before on the ship but I have recently purchased a new idea in smoke generators for the model boat world.It uses a nebuliser unit, which apparently uses frequencies of many times that used by cleaners, to generate water vapour from a unit placed into a boat hull. These things have been used for some time in the medical proffession for easing problems with breathing but the latest idea is to put them in a boat with an electronically controlled fan unit that works off the speed controller to generate a quantity of "Exhaust" relative to the speed of the motor.
They are very effective, use water, generate no heat and can be controlled to give very responsive smoke effects.
I'll get a couple of pictures sorted out later but I am very impressed.