But, this is not the only application, there are more.
The Netherlands is a country where bicycles are widely used. Many people use the bicycle to go to work, but the elderly also organize cycling tours, where they visit interesting places and stay in motion.
The application of the whistle at a cycling club for example, someone falls behind and is too far away to hear his/her call. With these whistles you give a clear audible signal, so everyone knows that something is going on. Because they are attached to a cord, the whistle can easily be hung around the neck, so you always have it at hand.