Hearing is measured in cycles per second(c.p.s) or hertz. The human range is from a base tone of 20 c.p.s. to a high-pitched sound of approximately 20,000 c.p.s. Any sound over 20,000 c.p.s is referred to as ultrasonic. Dogs can hear noises ranging from 20 c.p.s. to an amazing level of at least 35,000 c.p.s. Dogs learn to locate the source of a sound with great accuracy, using their large mobile ear flaps. Experiments have shown that they are able to pinpoint a sound within five degrees when it is placed anywhere in a circle of 360 degrees.

Dogs often react to ultrasonic sound which are too high for us human to hear. Dogs may become excited and start running around or barking. Elderly dogs sometimes become deaf which can make it appear as if they are ignoring your voice signals. If your ageing dog is becoming deaf, increase the use of hand signal. Dogs will quickly react to noises which signify enjoyment such as the sound of the family car engine, the sound of food being prepared, or the owner's footsteps.

Dogs react quickly to high, sharp sound such as a key in a lock, or the sound of scissors cutting up silvers of meat. This suggests that dogs will be interested in similar voice signals and will be more likely to respond to them. Dogs will always react to a hissing sound made through the teeth. Saying 'sit' or 'stand' in a similar way will elicit extreme interest. It is always better to use high-pitched voice signals rather than low, commanding ones. When calling a young puppy from a distance, it is better to move away from it while you say 'come', so that your movement will help the puppy to find the source of the sound.