Active vs. Passive Noise Reduction:
 
"Noise canceling" headphones (or more properly, headphones with built-in
noise-reduction circuitry) are designed to reduce background noise in
inherently noisy environments, such as in an airplane or bus. With noise 
reduction, you won't have to 'crank up' your player's volume to hear your 
music over the background noise around you. 

Traditional headphone designs use physical isolation to keep out external
noise. The isolation comes from thick padding around the ears and closed 
ear cups. This is called "passive noise reduction" because it does not 
require any electronic noise reduction circuitry. 

"Active" noise reduction circuitry can be incorporated into a headphone
design, which can block out low frequency rumble that simple physical
isolation can't.  The circuit usually consists of microphones that sense 
the ambient noise of the environment you're in, with circuitry that 
electronically cancels out this noise in the playback from the headphone's 
speaker drivers. 

The Turtle Beach ANR-10 headphone is a "behind-the-neck" model with good
physical isolation that also incorporates active noise reduction of up to 
-12 dB. The ANR-10's soft ear cushions and over-the-ear design have much 
better passive isolation than most similar models. When coupled with its
active noise reduction circuitry, the ANR-10 gives you great private listening
in a lightweight, comfortable package. It's a best choice for those who need 
a low-profile, portable package with great performance. 

The Turtle Beach ANR-20 headphone is a full-size model, with deep, soft ear
cushions that provide excellent passive isolation. In addition, the ANR-20 
employs an active circuit that provides an additional -20 dB of noise 
reduction! The sound quality is top-notch, with robust bass response, thanks 
to the full sized drivers and ear cup/enclosures. The ANR-20 is the top 
choice for listeners who demand the very best in sound quality and acoustic
isolation from a portable, foldable headphone. 
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