High Frequency Whistle ? with frequency guard, guarantees a uniform tone frequency. ? individually tuneable. ? very quiet. - Dogs primarily react to tones and acoustic signals but not to language. They learn easier with consistent tones and signals. The high frequency whistle is ideal for training and hunting. Its sound differs clearly from the day to day sounds with which the dog is normally confronted. The pitch of the high frequency whistle will be perceived by the dogs because of their bigger audio frequency. The pitch can be set by the help of a set screw which is under the plastic cap.