The Whistler

Every night beginning as early at 11:30pm, but usually closer to midnight or 1am, I hear someone blowing a whistle. "Woooooooooooo"....."Woooooooooooo"....whistling begins to sound further away...."woooo"......whistling comes back...."Wooooooooooo". Who/What/Why is this? Well, it's our neighborhood watchman, apparently, who rides around on a bicycle at night, blowing his whistle to alert everyone that all is well and safe in da hood (or he is just assuring us that he is out doing his duty). India....what a place.