Hear Doggy! toys give your pet the same sensation and enjoyment of traditional squeaky toys without the irritating noise! The science behind Hear Doggy!: Dogs can hear sounds at a higher frequency (0 to 45KHz) than humans (0 to 20 KHz). Tuned to an ultrasonic range in the 24-28 KHz frequency, each Hear Doggy! squeaker is out of human hearing range, but still fun for your four-legged friend. The Chew Guard lining was specially engineered to withstand tough play. All seams are double stitched and reinforced. Dogs are tough but chew guard is tougher!