The QZ77 Stereophone features both Active Noise Reduction (ANR) technology and Passive Noise Reduction (PNR) technology which eliminate harmful and unwanted noise while still providing the ultimate in stereo sound.

The ANR technology utilizes tiny microphones embedded in the ear piece. These microphones sample the surrounding low-frequency noise and transmit information about those undesirable sounds to a processing circuit. The processing circuit, in turn, generates mirror image "anti-waves" that are 180 degrees out of phase and relays those anti-waves back to the stereophone. When the offending sound waves encounter the waves generated by the QZ77, the two counteract each other at the wearer's ear. The offending hum and buzz is reduced and a peaceful listening environment is created where once there was noise. Low frequency noise below 1000 Hz, such as jet, bus or automotive engines, is reduced by an average of 10 dB. Noise reduction is even greater for noise below 200 Hz, offering a 15 dB of protection against low frequency noise.

Designed after another popular Koss model, The Plug, the stereo earbud features a dynamic element that is positioned just outside the ear. The element is connected to a tubular port structure that is inserted on a soft expandable cushion into the ear canal. Soft foam "memory" cushions expand for a custom fit to improve isolation and enhance deep bass and treble clarity. Utilizing the fit and mechanical design of the headphone to reduce noise is known as Passive Noise Reduction (PNR).

While the ANR circuit reduces low frequency noise, the PNR reduces high and mid frequencies so music and voice can be heard in absolute clarity. Double noise reduction and maximum sound performance all in one complete product.

Our Price	$39.09
Availability as of 3:46am 11/21/2009	Special Order. Allow approximately 2-3 weeks for delivery. Click to Verify Price and Stock
Condition	New and Factory Sealed
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