i can her it, it freaks out my cat too and i can hear a similar sound from tvs
adults can't her it because their ears are worn more than kids ears and not as sensitive to high pitched sounds.
the sound is sometimes used to deter children and teenagers from places. it is played really loud through speakers it is commonly used in skate spots, strip clubs and sex toy shops or places where kids do drugs and anywhere else where kids shouldn't be. it deters kids but not adults. adults simply cant hear it