How is an echo defined?

An echo is defined as a sound that is perceived later than the original sound due to the reflection of sound waves off a surface. When sound waves travel and encounter a solid surface, such as a wall or a mountain, they can bounce back, resulting in the listener hearing the original sound and its reflection after a brief delay. This phenomenon is why echoes are commonly experienced in large, open areas or spaces with hard surfaces.

The characteristic of an echo being a delayed response is crucial, as it differentiates it from other sound phenomena. For instance, a repeated sound perceived immediately aligns more with reverberation, while an increase in sound amplitude refers to a sound becoming louder rather than delayed. Similarly, a complete cancellation of sound waves describes interference rather than the experience of hearing an echo. Understanding these differences helps in appreciating how sound travels and interacts with the environment.