Purchased this due to excessive barking from both of my neighbors' dogs. I half expected the device to be a waste of money but it worked extremely well with one of the dogs(small terrier mix)-he instantly stopped barking and moved to the far corner of the yard. I tried it with the other neighbor's dog (chocolate lab mix), he stopped mid bark and tilted his head but I had no discernible results on subsequent uses. It does seem more effective on felines.