Trixie high frequency whistle with frequency protection Dogs react primarily on tne and acoustic signals and not on language. The high frequency whistle is therefore ideally suited for training. It differs in its sound quite markedly from the usual Geruschen with which your dog is faced day for day. Dogs have a much Full-Size tonal range and take these Tne true in the same loudness as a normal dog whistle. So please note that even a slight whistling is perfectly adequate. since too loud Tne can rather scare your dog.