Why Can't Humans Hear Dog Whistles?

It is fascinating to watch a person blow a whistle, yet to hear no sound. Nonetheless, dogs in the neighborhood start to bark and some even come running. What do the dogs hear that we can not, and how does this all work?

  1. The Physics of Whistles

    • Whistles are aerophones because they make a sound by forcing air through an opening, much the same way as organ pipes and oboes do. You may have noticed that when you blow a whistle, only one pitch comes out. That is because the distance between where you blow into the whistle and where the sound comes out of the whistle never varies. Bigger whistles emit lower tones than do little whistles, which emit higher notes. The basic principle here is that the shorter the distance the air has to travel through a resonating tube or chamber, the higher the note will be. This can also be influenced by the diameter of the tube: skinnier resonating chambers will produce higher pitches.

    Sound Production

    • If you look at a whistle (or an organ pipe), you will notice that at the point at which the sound comes out of the resonating chamber there is a sharp metal or plastic edge. This is what actually produces the pitch. The air you blow into the whistle rushes through the resonating chamber on its way out of the instrument, but can only leave the whistle once it has been "cut" by the hard edge.

    Human Hearing

    • The range of normal human hearing has been determined to be 16Hz to 16,400Hz. 16Hz are very low-pitched sounds and 16,400Hz are high-pitched. A Hz (Herz) is a complete cycle of a sound wave. Sixteen Hz means the pitch vibrates 16 times in one second. Some people with excellent hearing can hear as high as 20,000Hz. As we age, our hearing deteriorates, and our upper range is usually the first to diminish.

    Canine Hearing

    • Dogs can typically hear in the range of 60Hz to 60,000Hz. In other words, it can hear a much wider range of high-pitched sounds than can humans. Hearing is such an important sense to dogs that their ears have eighteen muscles in them so when a dog hears something, it can position its ears properly for maximum reception, even without moving its head.

    Dog Whistles

    • Dog whistles emit sounds in the range of 20,000Hz to 48,000Hz. Some dog whistles have sliders on them to produce variable pitches. They are sometimes called "silent whistles," but only because we humans can't hear them. Dog whistles are effective with our pets because the animal is not used to hearing such high pitches in our man-made world. Pitches higher than human hearing get a dog's attention very quickly.