The MDR-NC100D Digital Noise Canceling In-Ear Headphones from Sony provide high-quality audio & noise cancellation in a compact & lightweight design thats ideal for travel. The headphones have closed-type vertical housings & 3 sizes of noise-isolating eartips that provide a secure & comfortable fit. There are 13.5mm dynamic drivers with a digital equalizer & a fully digital S-Master amplifier to provide crisp, detailed audio with a wide frequency response & high dynamic range. The headphones pack a wealth of technology to cancel out unwanted noise, allowing you to focus on your music. The headphones use Sonys unique DNC software engine to create a high-precision canceling signal. There is also an Artificial Intelligence Noise Canceling function, which sets an optimal noise canceling mode based on intelligent analysis of the environmental ambient noise. The headphones also offer a monitor function that means that you can hear your surroundings without removing the housings from your ears. All of the active technology operates on a single AAA battery. If desired, you can also use the headphones in a standard passive mode to listen to music without the cancellation features, even if the power switch is set to "off". The neck-chain style cable provides plenty of slack & has OFC Litz wiring to provide a clear signal path with low degradation. The gold-plated 3.5mm stereo mini plug is angled for strain relief, & offers wide compatibility with a variety of CD players, MP3 players, laptops, & other devices. A dual-prong plane adapter is included for easy connection to in-flight entertainment systems.