While it is true that sound waves propagate faster in solids compared to gases or liquids, sound waves can still reflect off solid surfaces and create echoes. The reflection of sound waves occurs due to the change in the medium's properties or shape, causing the wave to bounce back.
When a sound wave encounters a solid surface, such as a wall or a rock, some of the wave's energy is transmitted into the solid, while some of it is reflected back into the air. The solid surface acts as a boundary, causing the sound wave to change direction. This change in direction is known as reflection.
The ability of sound waves to reflect from solid surfaces is due to the difference in the acoustic impedance between the two media (the solid and the air). Acoustic impedance is a property that depends on the density and the speed of sound in a particular medium. When sound waves encounter a medium with a different acoustic impedance, part of the wave's energy is reflected.
The reflected sound waves travel back to the observer's ears, creating an echo. The time delay between the original sound and the echo depends on the distance between the sound source and the reflecting surface. This delay is perceived as the time it takes for the sound to travel back to the listener.
It's important to note that even though sound waves propagate faster in solids, the reflection phenomenon is not solely dependent on the speed of sound. Reflection can occur in any medium, including gases and liquids, but it is often more noticeable with solid surfaces due to their higher acoustic impedance compared to air.
In summary, sound waves can reflect off solid surfaces due to differences in acoustic impedance, creating echoes that we can perceive. The speed of sound in solids influences the overall propagation of sound but does not prevent reflection from occurring.