Echo:
An echo is a sound that is reflected back to the listener after hitting a surface. It is a distinct repetition of a sound that occurs when the original sound waves bounce off a surface and return to the listener's ears. The time interval between the original sound and its echo is determined by the distance between the sound source and the reflecting surface. Here are some key points that differentiate an echo from reverberation:

1. Reflection:
- An echo occurs when sound waves reflect off a surface and return to the listener.
- The reflecting surface needs to be at a significant distance from the sound source to create a noticeable echo.

2. Delay:
- The time delay between the original sound and its echo is usually perceptible.
- The delay is a result of the time taken for sound waves to travel to the reflecting surface and back.

3. Repetition:
- An echo is a distinct repetition of the original sound.
- It is heard as a separate sound event, occurring after the initial sound has ceased.

Examples:
- When shouting in a canyon, the sound waves bounce off the canyon walls and produce echoes.
- Clapping hands in an empty room can also create echoes.

Reverberation:
Reverberation refers to the persistence of sound in an enclosed space after the original sound has stopped. It is caused by multiple reflections of sound waves from various surfaces within the space. Here are the key differences between reverberation and an echo:

1. Multiple Reflections:
- Reverberation occurs due to multiple reflections of sound waves within an enclosed space.
- These reflections blend together and create a continuous sound effect.

2. Continuity:
- Unlike an echo, which is a distinct repetition, reverberation is a continuous sound effect that lingers in the environment.

3. Indistinguishable Repetition:
- The individual reflections in reverberation cannot be distinguished by the listener.
- The resulting sound appears as a blend of multiple reflections, creating a dense and prolonged effect.

Examples:
- Singing in a large hall or performing in a concert venue often produces a reverberant sound.
- The sound of a bell ringing in a cathedral can also create a prolonged reverberation.