We don't know how the engineers at Direct Sound did it but they achieved a 29 db reduction passively.  No batteries! No electronics.  That means nothing to break or wear out. 

Noise Reduction Headphones Save Your Ears

These noise reducing or canceling headphones cut down the outside noise by 29 db, so you can set the headphone volume on a low to medium setting and save those ears.  Headphones that don't reduce the outside noise need to be loud to be heard.  Ouch, that hurts the ears, and can cause permanent damage. The 40 mm drivers in these noise canceling headphones are so good that they can be used with your CD player.  

Drummer Headphones With Unbeatable Comfort

The ear muffs and fit of these noise reducing  headphones have been refined over the years to be the most comfortable headphones available.   Remember that these headphones are created by a drummer, so you can wear these for hours without fatigue and ear discomfort. 

Hear Each Stroke

When used as drummer headphones the reduction in  ambient noise allows you to hear your drum strokes more distinctly. 

Specifications:

TYPE: Dynamic Closed Back Speakers Inside of a Closed Back Ear Muff is Direct Sound
FREQUENCY RESPONSE: 20 - 20,000 hz
DRIVERS: 40 mm
IMPEDANCE: 32 ohms
SENSITIVITY: 103db at 1000 hz.
CORD: 9 feet
PLUG: stereo 3.5mm w/gold plated 1/4" adapter
FEATURES: Advanced an-isotropic magnet drivers for superior Fidelity and Sensitivity.

Eliminates surrounding sounds by up to 29 db. making it possible to record "LIVE" drums next to the mixer board in a one room project studio (by using two sets of headphones).

Uses:

For SOUND ENGINEERS to monitor the mixer board during live performances while isolating their ears from main speakers.

For STAGE AND STUDIO DRUMMERS who want to hear how drums are being mixed without having head-phones at high volume.

Allows STUDIO MUSICIANS to hear only the studio mix during recording - eliminating costly return trips to the control room.

For STADIUM AND DOME EVENTS - listen to "LIVE" broadcasts at medium volume and block out most stadium noise while watching the game.

Headphones fold for easy storage - Convenient dual cords worn behind head.

• Types of Headphones

  Headphones are used not only for private entertainment, but also for professional monitoring. The most common uses and for field recording where a loudspeakers would be impractical or for musicians in the studio who need to hear each other or previously recorded tracks for overdubbing.