These are right up there among the very best noise cancelling headphones.

The Sony MDR-NC500D uses what's known as feedback type noise canceling, meaning the microphone is placed near the ear rather than on the outside of the earcup.

For the non-geeks among us, that means that the headphones cancel the sound that is actually reaching your eardrums, rather than the sound that is outside the earcup itself.

For low-cost headphones that isn't much of a distinction, but the Sony MDR-NC500D combines a number of high-tech features to deliver the best possible result.

These headphones also use a digital equalizer combined with a software engine which enable the headphones to react to different environments, such as an airplane, a train, or an office, which all generate different types of noise.

By changing the position of a switch on the earcup, you can change the setting that optimizes the noise-canceling performance according to whether you are on a plane, train or in the office.

That's pretty cool, and makes complete sense. The sounds you are trying to get rid off in a plane are very different from those in an office, for instance.

These are the core technology features of the Sony MDR-NC500D. Beyond that, these are sturdy, comfortable headphones with some great features and accessories, including a hard-shell carrying case.

They are not inexpensive, but with noise-cancelling headphones you really do get what you pay for.

The Deal: Get your Sony MDR-NC500D Digital Noise Canceling Headphone from Amazon.com for $304 (A saving of over $95).