How does sound reflection create echoes?

Sound reflection creates echoes when sound waves bounce off a surface and return to the listener after a noticeable delay.

Sound is a type of energy that travels in waves. When we make a sound, it travels through the air in all directions until it hits a surface. If the surface is hard and flat, like a wall or a mountain, the sound waves will bounce back, or reflect, towards the source. This reflected sound is what we hear as an echo.

The key to hearing an echo is the delay between the original sound and the reflected sound. This is because sound travels at a finite speed - approximately 343 metres per second in air. If the reflecting surface is close, the delay will be too short to distinguish the echo from the original sound. However, if the surface is far enough away (typically at least 17 metres), the delay will be long enough for our brains to perceive the original sound and the echo as separate sounds.

The strength or loudness of the echo depends on the reflecting surface. Hard, flat surfaces will reflect more sound energy and produce a louder echo. Soft or irregular surfaces will absorb more sound energy or scatter it in different directions, resulting in a weaker echo or no echo at all.

In summary, an echo is created when sound waves reflect off a surface and travel back to the listener. The distance to the reflecting surface determines whether the delay is long enough to perceive the echo, and the nature of the surface affects the strength of the echo.