The most effective way of soundproofing a door is to apply soundproofing rubber to the door perimeter or use weatherstripping. Other methods involve installing a door gasket, acoustic panels or solid core doors to absorb sound waves effectively. 
When compared to old houses, modern-day apartments are noisier due to faulty construction, open floor designs, and extensive use of entertainment devices. These make soundproofing a necessity in many situations, such as if you have neighbors who create a ruckus or when working from home. 
In such cases, soundproofing the door should be the priority since it is the main entrance to the house. So, my guide explains the most effective methods to accomplish that. 
How To Soundproof A Door

Best Door Noise Reduction Techniques 1. Installing A Door Gasket
When sound travels through gaps, it gets amplified. Such gaps are usually present around the door frame, which can be blocked using a door gasket. A door gasket is generally made from high-quality neoprene and attaches easily to the top and sides of the door jamb, effectively blocking out sound. 

You can find many types of door gaskets on the market to soundproof your door, even vinyl and adjustable ones. These also block moisture, dust, and light and can be used on doors that may not be rectangular or are warped. 
2. Applying Soundproofing Materials To The Door Perimeter
Another excellent method you can try is to apply soundproofing materials to the door perimeter. Such materials...