Is ultrasonic noise from small turbines painful to pets? A question on another SE site prompted me to search for 'Aircraft engines untrasonic noise dogs', but with not much success.  The OP's dog barked like crazy at turboprops, but was not bothered at all by 'louder' noises from light GA planes with piston engines, even when led next to them as the engines ran up on the ground.

Does anyone know how much ultrasonic noise does a small turboprop put out?  I suspect that it may be worse, in proportion, to that from the large turbofans on airliners since the hp shaft revs so high on those little engines.

Maybe that noise that is merely an annoyance to humans is actually painful to dogs etc?
This answer lists a number of RPM values for different aircraft engines. A typical small turboprop engine, the PT6, runs its core at 45,000 RPM and the power turbine at 30,000 RPM, which should produce sounds in the ultrasonic region.

The picture below shows a cutaway of a PT6 (source); if you count the blades and take the result times 3 (the cutaway spans 120°), the high pressure turbine disc shows 54 blades and the power turbine 42 blades.



Each time one of those blades runs through the wake of a stator blade ahead of it, it will create a pressure change with a frequency of 30,000·42/60 = 21 kHz and 45,000·54/60 = 40.5 kHz. At idle power, the speed is a bit lower, but not by much. 

So, yes, the dog might very well have heard a noise inaudible to humans.