Sound

1.why is the sound producer in air, not heard by a person deep inside the water?
2.if a person sets his watch by the sound of a distant suren, will it go fast or slow and why?
3.A stone is dropped into a well 44.1m deep.The sound of the palash is heart 3.13 s after the stone is dropped.Find the velocity of sound in air. Take g=9.8 m /s.s .  {339.2m/s}
4.The sound of the spasht of a stone dropped into a well is heard 3 s later.What is the death of the well? Take speed of sound in air as 343 m/s.             {40.62m}
5.A boy strike a long aluminium rod at one end.Another boy at the other end with his ear close to the rod, hears the sound of blow twice with an interval of 0.120 s.Find the length of the rod. Take velocity of sound in air as 343 m/s and velocity of sound in aluminium as 6420m/s.     {43.48m}