I use the whistle very cautious if I eg not pervade the cycle track with the voice or with the bicycle bell (Which is unfortunately more and more often the case, because many people pursue their sport with Stöppseln in the ear, which makes them almost inaccessible to "normal" sound) Anyway, I can do it almost always that I will eventually still noticed - if necessary with "full volume" The bell I go constantly around his neck, which gives a good feeling of security