Dogs respond to whistles for several reasons:

1. Training: Dogs can easily be trained to respond to whistled commands. Whistles provide a consistent sound that dogs can easily recognize and associate with a command or an action. Through positive reinforcement, they learn that responding to the whistle means rewards or praise, reinforcing the behavior.
2. Auditory Sensitivity: Dogs have keen hearing and can detect a wide range of frequencies, including the high-pitched sound of a whistle. Whistles cut through background noise and travel long distances, making them effective for communicating with dogs, especially in outdoor environments where they may not hear you.
3. Distinctiveness: Whistles are distinct from other noises in the field, making them stand out to dogs. This distinctiveness helps dogs differentiate between everyday sounds and commands. A very distinct sounding whistle can also help differentiate between you and another handler.
4. Consistency: Whistles produce consistent sounds compared to human voices. This helps dogs understand exactly what you’re asking of them and to respond the way you want, no matter who is handling them.
5. Versatility: Whistles can be used for different commands and behaviors, like recall, signaling the start (or end) of an activity, or directing the dog's attention. With field dogs, they are usually a signal to hunt on.
6. Non-verbal Communication: Whistles provide a form of non-verbal communication that transcends language. This is especially useful in situations where multiple handlers are working with the same dog or when giving commands across distances.

Auditory Sensitivity might be the number one key for training a hunting/field trial/hunt test dog. A dog’s sensitive hearing can pick out the sound of your whistle and carry out their mission. That being said, you can overdo it. The sound will become meaningless to your dog if they hear it constantly, and your hunting buddy or bracemate won’t have to endure the constant noise!