The stv728 the big cheese sonic repellers use powerful ultrasound that drives mice and rats from the home the 3 repellers produce ultrasound at constantly changing frequencies which are too high for humans dogs or cats to hear but which are within the hearing range of rats and mice each unit protects an area of at least 37 square metres 400 square feet from infestation by rats and mice is an apparatus which can be used to repel rats and mice the unit pack displays directions for use and