Final answer:
Reflection of sound waves is known as an echo, which occurs when sound waves hit a surface and are reflected back to the source, creating an audible repetition of the sound after a short delay.
Step-by-step explanation:
Reflection of sound waves produces the phenomenon known as echo. When sound waves collide with a large object or surface, they are reflected back. This can be experienced when you are in a large empty hall and you shout; the sound you hear a split second later is the echo of your own voice returning to you. This reflection of sound is also what enables us to hear our voices when we are near a mountain cliff in an open space with no other objects around to absorb or scatter the sound.
In terms of the physical properties of sound, an echo is a reflection that occurs when the sound waves hit a barrier and change direction, returning to the source. The condition for this to happen is usually an open space with large surfaces that can reflect the sound without too much absorption. For the reflection to be perceived as an echo, there must be a sufficient time delay between the original sound and its reflection, otherwise, it will not be discernible to the human ear.