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"My son, Billy, picked up this silent dog whistle at a pet supply store." My friend George held out his hand to show me a small shiny metal whistle and then he continued, "Billy said that he was told that it is useful in controlling a dog's behavior — like calling them to you. He was also told that it could also be used to stop a dog from barking. I tried using it with Boo-Boo [George's standard poodle] but it didn't stop her when she was barking and she certainly didn't come to me when I blew it."
We were sitting in my house drinking coffee, and George put down his mug and blew on the little whistle as if he wanted to demonstrate how it worked. All that I heard was the faint hissing of his breath; however, my Cavalier King Charles Spaniel, Ripley, started to his feet and began to bark excitedly.
George gave a little laugh and said, "At least your dog responds to it. Boo-Boo acts as if she doesn't hear it all."
The silent dog whistle actually started out as a research device. It was first described in 1876 by the eccentric genius Sir Francis Galton in his book Inquiries Into Human Faculty and Its Development and scientists refer to it as Galton's Whistle.
His original device was a small brass whistle with a slide which allowed him to alter the whistle's frequency. The idea was to test the range of human hearing.
Galton then went on to repeat the same hearing experiments on a variety of animals including dogs. He found that dogs could hear high-pitched sounds that were well beyond human hearing ability. Thus the maximum upper sound frequency range of human hearing is about 20,000 Hz for children, but by the time a person is around 30 years of age, it will have declined to about 16,000 Hz. The top end of the dog's hearing range is about 45,000 Hz*.
To give you an example of what this means, if we wanted to extend the right side of a piano keyboard to the limits of human hearing, we would have to add 28 keys. If we extended the keyboard to match a dog's hearing, we would have to add 52 keys — and the last 24 of these would produce sounds that were so high-pitched that humans cannot hear them.
Most scientists believe that the wild ancestors of our dogs evolved the ability to hear high-pitched sounds in order to allow them to hear the high-frequency noises made by the small prey animals that they hunted when they were rustling around in the grass and leaves or scratching at the ground.
So it should be clear that silent whistles are not silent. Typically the most common of whistles with a fixed frequency tend to produce a tone which is around 35,000 Hz. This is easily heard by dogs but is beyond human hearing (see the figure below).
However, the majority of these dog whistles are adjustable because the higher frequencies, which easily get the attention of small dogs, are often not responded to by larger dogs. That means that if you are using a silent dog whistle, you must adjust it to the optimal frequency for your dog.
One way to find out which frequency is right for any particular dog is the "wake-up" test. Start when the dog is asleep and blow the whistle. Then in small steps, adjust the frequency until the dog is awakened by the noise (which will still be inaudible to you). Alternatively, working with a dog that is awake, you can adjust the frequencies until you find one which causes the dog's ears to twitch or one that causes him to turn his head reliably in your direction.
The primary advantage associated with such dog whistles is that the sounds that they make, although imperceptible to humans appear to be quite loud to dogs. That means that dogs can hear these signals over longer distances than they might be able to hear the human voice, even when a person is shouting. For this reason, dog whistles are often used while hunting, since it is more likely that human voice commands might not carry a sufficient distance.
Another advantage is that these high-frequency sounds are less likely to spook the wildlife than the sound of a human shouting. Herding dogs are also often trained to respond to whistle commands and dog handlers in the police and military services often use such whistles as an alternative to verbal commands.
Surprisingly, a dog that is suffering from hearing loss may still respond to whistle training. By using a frequency-adjustable silent whistle, the dog's owner may be able to find a frequency that is within a range that the animal can still hear. Although not every deaf dog still retains hearing within a range that the whistle produces, it is successful in enough cases to be worth a try.
Please note that the silent whistle does not have any mysterious qualities. It is simply producing a sound that the dog can hear and you can't. That means that if you want a dog to respond to that sound you must train him in the traditional way, much like you would train a dog to respond to the sounds of the verbal commands "come", "sit," or "down."
The most persistent myth about silent dog whistles (or their electronic equivalents which also produce the same ultrasonic high-frequency sounds) is that these sounds will make a dog stop barking, stop fighting, or terminate other ongoing annoying behaviors.
Unfortunately, the available scientific data fails to confirm these expectations unless the dog has been trained to associate these specific sounds with rewards or punishments. In some cases attempts to use a whistle have backfired because the sound it produces may be irritating or annoying for a dog and might actually provoke them to bark, howl, or act in an excited manner — as was the case when my friend blew the whistle which provoked my dog Ripley to bark.
I then went on to explain to George that perhaps the most useful application of the silent whistle was to teach a dog to return when he hears the sound that it makes. Since this high-frequency sound carries a longer distance than the human voice, it can be used indoors to call the dog to you, no matter which room in the house the dog happens to be in at the time — all without disturbing the other members of the household. It can be used outdoors when the dog has strayed a distance or may be out of sight.
However, the dog has to be taught to respond to this signal the same way that you initially taught the dog to return to you when you gave the verbal command "come" or a hand signal to call him to you. I then went on to remind George of the time when his dog Boo-Boo slipped out through an open gate. "Remember that you told me about how embarrassed you were when you had to spend half an hour wandering through the neighborhood shouting 'Boo-Boo come!' You know if you had trained her to come to a silent whistle command then you could've managed to get her to come back without disturbing your neighbors and drawing attention to yourself. Like the old proverb goes, sometimes 'Silence is golden!'"
Stanley Coren is the author of many books including The Wisdom of Dogs.
Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.
References
Coren, S. (2004). How dogs think: Understanding the canine mind. New York: Free Press.
