This particular whistle is a Chinese knock off and does not perform as well as an authentic Fox40 whistle.  I received this whistle and was concerned that it took significant power to create a sound, so I contacted Fox40 and they confirmed that this whistle was not manufactured by them.  The seller "Poolweb" is obviously selling defective Chinese knockoff whistles which could prove useless in a crisis situation.... DO NOT PURCHASE THIS WHISTLE FROM POOLWEB!!.