Dogs can hear sounds at higher frequency than humans. Duvo+ Heardoggy features a patented squeaker that is tuned to an ultrasonic frequency which is out of human hearing range, but still fun for you 4 legged friend. Manufactured with the super tough durable liner that makes it strong enough to stand up to even the toughest play. * Dog toy with ultrasonic sound * No annoying noises for owners * Super-strong plush toy * Durable ChewGuard technology