I am an expert in this area--one of the poineers. Even did
early work on lowland gorillas, the California condor and horses.
The only problem with unltrasound in the fetus was small
birthweight in those having many studies--caught up by age 2--and
only found in Canada.
Sonography technologists have their hands on the transducer
(source and receiver of sound waves) most of their working day,
say six to seven hours. No problems. Like anything in science,
who knows what will happen in thirty years.
Your fingers should turn to prunes and the tips rot from the
liquid long (??decades) before the sound waves have any
appreciable effect on them. I you leave your fingers in the
water, cleaning solution, whatever, for six to seven hours a day,
your problem is much more interesting than anything you have
admitted to so far.
As to indirect contact, ultrasound cannot maintain strength when
it travels through air as a rule. You're not deaf, just
ignoring your spouse.
Since ultrasound is now used for rodent/pest control, we will
learn in the next ten to thirty years if there is a problem.
However, in the past twenty years, nothing to write home about.
If your dog responds to your unit, let me know how (Ossi dogs
are somewhat unpredictable).