Panasonic RP-HC70

Noise-cancelling headphones work by creating "anti-noise" that exactly counterbalances external sounds at the ear.  While unable to cope with non-repetitive sounds, they do a good job of reducing the constant drone in an airliner cabin or the hum of a room air conditioner or computer fan.

  Noise-cancelling headphones began as an expensive, bulky laboratory concept, but Panasonic's RP-HC70 exemplifies their graduation to an affordable consumer product.  The least expensive model in the RP-HC line, they nonetheless offer good sound quality and up to 50 hours of active background noise cancellation from a single AAA alkaline battery.  Their lightweight folding design makes them ideal for travel, and the closed over-ear approach is courteous to other passengers.  The cord-mounted controller offers a volume control as well as a noise-reduction intensity switch.  Choose either maximum noise cancellation -- up to 70%, according to Panasonic -- or the less aggressive setting for more awareness of the sounds around you.  Large 1.2" drivers respond to frequencies from 40 Hz to 15 KHz.