What is ANC and do I need it?

Active Noise Cancellation uses microphones to detect ambient sound and generates inverse sound waves to cancel it. It's most effective against constant low frequency noise (airplane engines, train rumble, HVAC). It's less effective against sudden or high frequency sounds (voices, alarms). If you commute, work in open offices, or fly often, ANC is worth prioritizing. For quiet environments, it's less critical.