Materials that reflect sound waves the best are those with high acoustic impedance mismatch between the material and the surrounding medium (usually air). Acoustic impedance is a property that combines the density and speed of sound in a material.
Generally, dense and rigid materials tend to have high acoustic impedance and are good at reflecting sound waves. Some materials that are known for their excellent sound reflection properties include:
Metal: Metal surfaces, such as steel, aluminum, and brass, are highly reflective to sound waves due to their high density and rigidity.
Concrete: Concrete surfaces, especially smooth and dense ones, reflect sound waves effectively.
Glass: Glass also reflects sound waves well, especially when the surface is smooth and rigid.
Hardwood and Dense Woods: Solid and dense woods can be good sound reflectors, particularly when the surface is smooth and uninterrupted.
Stone: Materials like marble and granite can also reflect sound waves effectively.
It's important to note that the effectiveness of sound reflection also depends on the angle of incidence and the shape of the reflecting surface. Smooth and flat surfaces tend to reflect sound more efficiently than irregular or rough surfaces.
On the other hand, materials with low acoustic impedance mismatch tend to absorb sound rather than reflect it. Soft and porous materials like foam, carpets, curtains, and fiberglass are examples of sound-absorbing materials used for soundproofing and acoustic treatment purposes.