Sony MDR-NC500D

The Sony MDR-NC500D are the world's first headphones to have digital noise-canceling technology. This helps remove the background noise from planes, cars, trucks, buses, etc. while still providing a high-quality audio. Like all noise-cancelling headphones, there is a mic that samples ambient noise, which is then turned into an inverted wave that, when mixed with the audio playback, effectively cancels out the ambient noise. The difference in the case of these headphones is that the sampled ambient noise is converted and processed as a digital signal by the internal circuitry before mixed with the audio playback. It requires battery power, for which a rechargeable lithium-ion battery or the option of connecting to an external power supply that takes two regular AA batteries. The fully charged lithium-ion battery provides 16 hours, and two AA batteries used in conjunction with that provide 28 hours of battery life.