The difference between a material that reflects sound waves and a material that absorbs sound waves lies in how they interact with the sound energy.
Reflecting material: A material that reflects sound waves bounces the sound energy back into the surrounding environment. When sound waves encounter a reflecting material, such as a hard, smooth surface, they are not easily absorbed into the material. Instead, they are redirected in a predictable manner, following the law of reflection, much like light waves bouncing off a mirror. Reflecting materials tend to produce echoes and reverberations, as the sound waves keep bouncing off the surface until their energy dissipates.
Absorbing material: In contrast, an absorbing material is designed to reduce the reflection of sound waves by dissipating their energy within the material. Absorptive materials are typically soft, porous, and have irregular surfaces. When sound waves reach an absorbing material, the porous structure and irregularities within the material cause the sound energy to be converted into heat through friction and internal reflections. As a result, the sound energy is effectively reduced, and fewer sound waves are reflected back into the environment. Absorbing materials are often used to improve room acoustics by reducing echoes, controlling reverberation, and minimizing background noise.
It's worth noting that materials can exhibit both reflective and absorptive properties to varying degrees. For instance, a hard, dense material like concrete can reflect sound waves due to its smooth surface, but it can also absorb some sound energy due to internal friction within the material. Similarly, some materials can be engineered or treated with special coatings to enhance their reflective or absorptive characteristics based on specific acoustic requirements.