What is echo ? Why we cannot hear an echo in a small room ?

Explanation

### Step-by-Step Solution:

1. **Definition of Echo**:
- An echo is defined as the reflection of sound that arrives at the listener after bouncing off a surface. When sound waves travel from a source, they can hit a reflective surface (like a wall) and bounce back, allowing us to hear the sound again.

2. **Understanding the Mechanism**:
- When a sound is produced, it travels in waves. If these waves hit a rigid surface, they reflect back towards the source. This reflection can occur multiple times, creating multiple echoes.

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