Dogs hear higher pitch sounds than people. That's why dog whistles seem to be silent. Dogs hear the high frequency sounds that we can't. High frequency sounds usual travel further than voices and can be heard further away.

Dog trainers use dog whistles to get a dog's attention. Hand signals are often combined with dog whistles. Some find that different breeds react to different high frequecies. In general smaller dogs are most sensitive to higher frequencies compared to larger dogs.

Working Frequencies: 12000 to 40000 Hz