If you place your ear close to an iron railing which is struck some distance away, you hear the sound twice. Explain why?

Compare approximately the speed of sound in air, water and steel.

The sound of an explosion on the surface of a lake is heard by a boat man 100 m away and by a diver 100 m below the point of explosion.

(i) Who would hear the sound first — boat man or diver?
(ii) Give a reason for your answer in part (i)
(iii) If sound takes time t to reach the boat man, how much time approximately does it take to reach the diver?

How does the speed of sound change with change in (i) amplitude and (ii) wavelength, of sound wave?