uPVC doors are very good at being soundproof due to the conducting properties of the material but it is good to note that if you live on a busy main road, whilst it may reduce it drastically it may not eliminate it all together.

UPVC doors provide improved soundproofing in several ways.

The first is through their internal structure.  The UPVC shell is filled with insulating material, which is primarily designed to prevent heat loss, however it is also a very poor conductor of sound.  This means that unlike a traditional wooden door, where noises are carried through a single layer, with a UPVC door, the sound waves have to travel between multiple surfaces and as such, a lot of the noise is blocked and reflected back.

The second way that a UPVC door will help reduce sound indoors is through the close seal that is formed between the door and frame.  This prevents draughts from entering your home, but also removes a route for noise to get in too.  

While UPVC doors are not specifically designed for soundproofing purposes, they are an effective way of reducing noise.  If you have a specific requirement for noise reduction as part of your project, your installer will be able to advise you about which option is best for your needs based on their knowledge and experience.