What is the main function of a sound barrier in noise control?

The primary function of a sound barrier in noise control is to reflect sound waves away from sensitive areas. Sound barriers are typically structures built along roadways, railways, or other noise sources to mitigate the impact of noise pollution on nearby residential or sensitive areas, such as schools or hospitals. By reflecting the sound waves, the barriers effectively reduce the amount of noise that reaches these areas, thus helping to protect the occupants from disturbances.

While some sound barriers may have materials that provide sound absorption qualities, their main purpose is not primarily to absorb sound but rather to create a physical obstruction that diminishes the intensity of the sound waves that travel over or around them. This is why reflecting sound away is seen as their critical role in noise control.

The other options present functions that are either secondary to the main objective of sound barriers or unrealistic. For example, while soundproofing is a concept related to noise control, sound barriers cannot create a completely soundproof environment as sound can travel in various ways through the air and ground. Similarly, amplifying sound is contrary to the purpose of a sound barrier, and it's not designed to perform that function. Therefore, the function of reflecting sound away is effectively how sound barriers serve their role in noise management.