Probably this inquiry should base on the difference between the normal headphones and the noise-cancelling pieces. One key note to take is that these noise reducing headphones are categorized in two, depending on their work;  passive and active. Also Read: These are the different types of Headphones

Passive Noise Cancelling headphones

Typically, any type of head-phones can cancel noise passively because the materials in them are capable of blocking out external sound waves, especially if they come in at higher frequencies. They are closed-back and sealed to reduce noise passively by physically covering the listener’s ears to help block out external noises. They have an in-ear design that forms an acoustic seal that helps to block background noise and allow for more accuracy at lower volume levels.

In summary