STEVE SAYS: This whistle is a "silent whistle". It is used to give commands to dogs over distance just as any other whistle is used. It is called a "silent whistle" because it operates on a frequency above that of the average person's hearing. Most people will hear a faint sound. In other words it is very LOUD to dogs but very QUIET to people.
It is not a "silencer" and does nothing to make a dog stop barking nor will it repel an aggressive dog.
Read more about the European Style Silent Whistle by SportDOG
Light single body construction
Adjustable tone - Simply remove the black cap to adjust the tone to meet your dog's hearing capabilities
Made in China
Instructions:
This whistle produces sounds that are insignificant to the human ear but extremely audible to the more sensitive hearing of a dog. While it is not totally silent, this whistle is an excellent means of communication with your best friend without the annoying trill of normal dog whistles. With a range of up to 2 miles with optimum weather and terrain conditions, the European Silent whistle is adjustable for close and long range work.
Adjusting the Tone
Remove the black plastic cap to access the frequency adjustment screw. It is a tight fit, but it should snap off.
With your dog close by, start blowing the whistle. While adjusting the turn screw, observe at what frequency your dog reacts the most. When you can see an obvious reaction, tighten the lock nut and replace the black cover. Take the dog and the whistle outside and do the same thing. The results should be very similar.
Sometimes the cap can be difficult to remove. You may want to warm the plastic
cap with a hair dryer or some other heat source to make it easier. I have had good luck getting the cap off by sticking a pen or pencil halfway through the ring on the end and using it as a handle to pull with. Once it comes apart the first time it usually isn't a problem anymore. --STEVE