Instruct: Classify a given Amazon review as either positive or negative.
Query: Save your money

Had no appreciable effect on the local feral felines when two units were simultaneously placed at the entry points to my fenced yard. Cats didn't even twitch their ears when walking by and didn't seem at all discouraged from return visits. (And if you're near, the sound they make IS audible to humans - or at least to this one. (Didn't seem to dissuade a foul-tempered possum from entering the yard either.)