How is it possible to detect the filling of a bottle under a water tap by hearing the sound at a distance ?

“During the filling of an empty bottle with water, the pitch of the sound heard goes on changing." Why?

A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column. Why does the sound become very loud for this lenght of the water column?

A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column. Name the phenomenon taking place when this happens.

How frog respires under water?

Why are aerated water bottles kept under water during summer ?

A sound tone is produced under water. When it enters air

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

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