Dogs, cats and humans can all hear lowpitched sounds. But while humans can hear pitches only up to 20 kHz, dogs can perceive sound at 45 kHz and cats can hear the squeaks of their rodent prey up to 64 kHz. This ultrasonic hearing allows dogs to be trained with ‘‘ silent’’ whistles, while cats respond well to high voices. If you’ve wondered how your pet always hears the rustle of a packet, it might be because their ears can be turned to capture more sound. Their ears have 14 muscles, compared with humans’ six. A cat’s hearing allows it to distinguish the location of two objects only 7.5cm apart, from the distance of a metre – a necessary skill to locate hidden prey.