You CAN hear this thing! Well, maybe that's because I'm under 25, but yes - you can hear it.Did it work on my dogs? For a day. Then they started ignoring it.Day 1 I was hit with a migraine - I get migraines every once in a while, take RX medication for it, etc. At first I thought it was a coincidence, took my medicine, was fine. Then the 2nd day...another migraine. Then the 3rd. And the 4th.Don't even waste your money on this piece of crap. I have 2 "hard to train" dogs, but come on - this thing is a joke.