An astronaut cannot hear his companion at the surface of the moon because –

A worker was working on the rail track. A boy at a distance holds his ear near the rail track. This boy was able to hear sound of the blow of workman twice. It is because of :

How much should minimum distance be between the source of sound and reflecting surface, so that an echo can be heard clearly?

What is the phenomenon where sound waves bounce off a surface called?

Which of the following animals can hear the highest frequencies?

The sound created in a big hall persists because of the repeated reflections. The phenomenon is called