When do echoes typically occur?

Echoes occur whenever sound waves bounce off a surface and return to the listener's ears. This phenomenon can happen in various environments, including both enclosed spaces and open areas, as long as there are suitable surfaces for the sound waves to reflect off.

For instance, you can hear echoes in mountains, valleys, and even in empty rooms where sound waves hit walls or ceilings. The reflection of sound does not require specific conditions such as wind or particular sound frequencies. It's simply a matter of the sound waves encountering a surface that can reflect them. Thus, the notion that echoes can occur under such a broad range of circumstances supports the accuracy of this answer.